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The Botrytis Gray Mold Fungus: Pervasive Pathogen, Formidable Foe

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Introduction and Significance

When evaluating the impact and importance of a plant pathogen, one could consult various metrics to make such an assessment. One could consider the values of the affected crops, the acreages planted, the geographic distribution (how widespread is it?) of the pathogen, the mode of pathogen attack (does it affect leaves, flowers, both?), the persistence and staying-power of the organism, and the difficulty in controlling the pathogen. The Botrytis fungus, causal agent of gray mold and other related diseases, is one of the few plant pathogens that could arguably be placed at or near the top of a key pathogen list based on all of these criteria. Field professionals likely are familiar with the challenges of gray mold for the crops they oversee. However, what may be overlooked is the impact of Botrytis throughout a broad spectrum of many agricultural commodities and settings. Botrytis is an unusually dangerous threat due to its ability to infect dozens of crops, uncommon versatility as a microorganism, and propensity to change genetically in adapting to fungicide chemistry.

Table 1. Examples of Vegetative, Flower, and Fruit diseases caused by Botrytis on diverse crops.
*In contrast to most other crops diseases on onion are not primarily caused by Botrytis cinerea but by other Botrytis species.

Broad Spectrum Impact on Crops Worldwide

Botrytis is a highly ranked plant pathogen due to its broad host range that includes hundreds of plants. Such hosts are in almost all commodity groups: annuals and perennials, herbaceous and woody plants, food and ornamental crops, vegetable and fruit and field crops. Included within this diverse list are dozens of high value vegetable, fruit, and ornamental commodities (examples are listed in Table 1 and seen in Photos 1 to 4), for which gray mold can inflict sizeable economic losses. This broad spectrum of activity can also be described based on the type of plant tissue affected. Depending on the crop host, Botrytis can infect the vegetative portions (stems, petioles, leaves), flowering parts (buds, sepals, petals, reproductive tissues), and fruit (immature and ripe phases).

The Botrytis impact on all these crops and commodity groups is further compounded by two factors. First, the gray mold fungus can cause significant disease both before and after harvest. Pre-harvest disease occurs when Botrytis is active on developing plants in the field and greenhouse, resulting in blight, decay, and rot that reduces crop quality and harvestability. In addition, for many crops the Botrytis fungus can be a contaminant on or even inside the harvested plant commodity. Once these contaminated commodities are stored, the Botrytis fungus can become activated under certain postharvest conditions and cause rots and decay in storage (Photo 5). Secondly, we note that Botrytis is found throughout most agricultural and horticultural production regions in the world. In the USA, there are only a few states where an official report of Botrytis is lacking. Likewise, Botrytis is found throughout the world and is reported to cause disease on a huge number of crops and plants.

On pea, Botrytis can cause a pre-harvest disease but is perhaps more important as a postharvest problem, as seen by these lesions on stored pea pods.

Versatility as a Microorganism

A notable feature about Botrytis is the organism’s ability to function in different modes or survival strategies. This diversity of biological activity is not commonly seen in plant pathogens and points to the extreme versatility of Botrytis as a microorganism. Pathogen: We are most aware of Botrytis as an aggressive, difficult to control primary pathogen of plants. From an agricultural point of view, this is the most prominent role for Botrytis. Saprophyte: In a different mode, Botrytis does not even need a living plant. As a saprophyte, the gray mold fungus can grow, thrive, and reproduce on senescent, dying, and dead organic plant tissue. Spores that land on decaying matter can readily germinate and colonize such substrates. Secondary invader: If a plant is injured from weather extremes, damaged from mishaps in the field, or has symptoms caused by other pathogens, spores of Botrytis can drop onto such compromised plant tissues and aggressively grow on and overwhelm the injured plant. In such situations Botrytis did not initially cause the problem but is a secondary invader that can make the overall problem worse.

Dormant sleeper: Botrytis can be a sneaky adversary. This pathogen can infect and penetrate plant tissues but remain dormant within the protection of its host. Later, when the conditions change, the weather warms, or the plant tissues mature and grow, the once dormant Botrytis wakes up and begins to colonize the host, resulting in gray mold disease. Such dormant infections are called latent or “quiescent” infections. Opportunist: Botrytis is an opportunist because it can switch from being a harmless saprophyte, growing on dead tissue that growers do not care about, to an aggressive pathogen causing problems. Numerous examples exist of this switching. The Botrytis starts by colonizing dead parts of plants, such as old flower parts; if these Botrytis-laden dead pieces are in contact with healthy tissue, the Botrytis is able to bridge over from the dead to the living, resulting in a primary disease problem (Photo 6).

Gray mold is also versatile in how it survives and is moved around in the agricultural environment. Airborne spores: The gray color of the fungus, as it appears on infected plants, indicates Botrytis is producing millions of spores. These spore masses (Photo 7) are readily spread long distances by winds, splashing water, and physical contact. Sclerotia: Under certain conditions Botrytis can produce a survival structure, the sclerotium, which is a hard, black, oblong to spherical structure that can be up to ½ inch long. Sclerotia can withstand dry, warm, or cold conditions and can survive inside dead crop debris or buried in the soil; under conducive conditions these sclerotia can germinate and produce mycelium that infects the host. Sclerotia can form within the hollow stems of plant hosts and be carried with the plant if these stems are moved to other locations. Sclerotia can become mixed in with seed and become a seedborne contaminant. Embedded mycelium: In another survival mode, the hyphal strands of Botrytis can penetrate and be buried inside the living flowers, buds, or stems of plant hosts. This strategy allows the gray mold fungus to be protected from harsh environmental conditions, giving it an opportunity to wait for more favorable situations.

Botrytis can cause a brown decay on orange fruit by first colonizing dead flower parts that stick to the fruit; here the old blossom has been moved aside to show the developing brown lesion.

Genetic Plasticity and Loss of Fungicide Efficacy

Botrytis is notorious for becoming resistant (insensitive) to fungicides because of its high genetic variability and adaptability, profuse production of spores, and multiple cycles of spore production. Molecular recombination, mixing of genes between strains, and mutations provide the raw genetic material for resistance to develop. When fungicides are applied numerous times to a susceptible crop, the presence of the chemical challenges Botrytis and can result in the selection of individual strains that are no longer affected by that chemistry. Fungicides with single-site modes of action are especially at risk for inducing resistance in Botrytis. Worldwide, resistant isolates of Botrytis have been confirmed for all of the single-site fungicide categories used to manage gray mold (Table 2). Even more alarming are the research findings that show individual isolates of Botrytis can possess resistance to multiple fungicide classes; there are even isolates that are shown to be resistant to seven different fungicides, each of which has a different mode of action.

Table 2. Fungicide classes for use against Botrytis and for which resistance has been reported. *FRAC = Fungicide Resistance Action Committee

A Note About Botrytis Species

This article is addressing the broad topic of gray mold caused by Botrytis, and for most crops the pathogen species is Botrytis cinerea. However, examining the DNA of Botrytis from different crops in different parts of the world, powerful molecular tools and innovative techniques are detecting multiple, diverse genetic signatures which indicate that B. cinerea is not the only gray mold species out there. For example, a series of studies documents that strawberry can be infected by one or more of the following Botrytis species: B. cinerea, B. fragariae, B. caroliniana, B. mali, B. pseudocinerea. Such findings can have implications for the farmer and the field. On grapes in France, for example, the B. pseudocinerea species is more active in the early spring, while B. cinerea is active in both spring and fall. There are indications that a higher percentage of B. pseudocinerea isolates are resistant to some fungicides than B. cinerea isolates. So in the future it might be critical to know exactly which species is causing gray mold, since different species may require slightly different management approaches.

Management of Gray Mold

Controlling gray mold diseases requires the implementation of IPM practices. Fungicides: Judicious and strategic use of fungicides remains the primary means of managing gray mold. Multiple applications usually are needed, throughout the season, using diverse products having different modes of action. Fungicides with single-site modes of action are especially at risk for inducing resistance in Botrytis, so multi-site products should be integrated into spray programs. Sanitation: Sanitation measures, such as the removal of dead leaves and diseased fruit, appear to only slightly decrease gray mold incidence and cannot replace reliance on fungicide programs. Given the logistical difficulty and expense of such measures, these sanitation steps are not practical for most commercial growers but could be a consideration in certain circumstances, such as for greenhouse crop production.

Botrytis produces masses of airborne spores that readily land on host crops.

Modifying the environment: Because Botrytis is dependent on free moisture and high humidity, reducing such factors can help reduce disease severity. The venting out of moist air in a greenhouse is one example of such environmental modifications. Use of drip irrigation is a field equivalent of reducing water on foliage and can reduce gray mold severity. Canopy modification (pruning to remove leaves and laterals and increase air flow and light penetration) can help with bunch rot control in grapes. Resistant or tolerant cultivars: For most crops there are no cultivars that are genetically resistant to Botrytis. However, some cultivars may experience less gray mold for other reasons. For example, some strawberry cultivars suffer less gray mold due to the upright growth habit of leaves and flowers. Use such cultivars if available. Reduce damage: Reducing damage to crops in the field will reduce the opportunities for Botrytis to invade as a secondary decay organism. Proper harvesting and postharvest handling of fruit are critical to reducing fruit injury and lowering the impact from gray mold. Storing fruit at low temperatures is also necessary to retard gray mold and slow down the aging and senescing of fruit.

Screening of 1,000 Acala Cotton Lines

Work Completed

  • Selected 1,100 Acala Cotton Lines to be screened.
  • Prepared seed (ginned, delinted, treated, and packaged) for planting.
  • Planted seed in multiple testing locations.
  • Took multiple stand evaluations to determine the degree of FOV-4 damage.

Findings to Date

  • The year started off well with good stands on all Acala Lines.
  • Upon the completion of stand evaluations, we eliminated over 800 Acala Lines as being susceptible to FOV-4.

Work to Be Completed

  • Determine the degree of vascular staining in each Acala Line that has not already been eliminated from stand evaluations.
  • Rate each Acala Line based on productivity.
  • Assemble data and analysis throughout the year.
  • Complete Final Report.

Maintaining Fusarium Wilt Race 4 (FOV4) Resistance/Tolerance of Cotton

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The funded amount for this project from CCGGA is devoted to support travel to California for Dr. Ulloa and to assist in evaluation, progeny development, breeding and coordination of seed increases of selected developed progeny and breeding lines of Pima and Upland cotton for future testing and germplasm public releases with improved resistance/tolerance to Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4), a soil borne fungal pathogen. These FOV4 breeding research efforts and activities are coordinated and supported by the California team. In addition, funding partially pays for professional research/services support needed to increase our understanding of plant FOV4 defense mechanisms.

Over the past 14 years, the fungus that causes FOV4 has impacted fields in California’s San Joaquin Valley.  This fungus is particularly difficult to control in cotton as the hyphae or fungus- overwintering structures reside in the woody vascular tissues, preventing the penetration of fungicides. These structures can survive in soils indefinitely. In the United States, FOV4 was first confirmed in California cotton fields in 2003, however, in 2017 it was also identified in far-west Texas and in 2019 in New Mexico.

Cultivars with relatively high levels of resistance to FOV4 were originally identified in commercial Pima cotton (Gossypium barbadense L.), ‘Phytogen 800’, and originated-pool germplasm, ‘Pima S-6’. Field evaluation of cotton cultivars in FOV4-infested fields have provided information to develop a number of generalizations:  (1) most Pima cultivars show more severe symptoms and suffer higher levels of stunting and plant mortality from FOV4 than with most Upland and Acala cottons; (2) some moderate to highly-resistant commercial Pima cultivars have been developed from several seed companies and private breeders; and (3) several USDA-ARS experimental Pima germplasm or breeding lines with moderate to high resistance to FOV4 have been identified, developed, and publicly released (SJ-FR01 to SJ-FR09). These germplasm lines have helped to increase the genetic base for FOV4 resistance in Pima Cotton. Typical FOV4 symptoms are shown in Figure 1. Disease symptoms of this pathogen have been observed to differ between Pima and Upland cotton.

Figure 1. Foliar and root symptoms of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4). A) Foliar symptoms for Pima (Gossypium barbadense L.) cotton and B) Foliar with no visual symptoms and root with vascular root staining symptoms for Upland (G. hirsutum L.) cotton. (All photos courtesy of M. Ulloa.)

From 2006-18, we have been evaluating Pima germplasm from the USDA ARS and international breeding collections, and Upland germplasm from the USDA ARS Cotton Germplasm Collection College Station, Texas or breeding lines from around 13 public (universities and USDA) cotton breeding programs across the Belt through the regional breeder testing network or RBTN sponsored by Cotton Inc. and have provided information about the level of FOV4 tolerance of these breeding lines and germplasm. In addition, since 2013, more than 4,000 entries and developed progeny have been evaluated in infested FOV4 fields and a portion (1/4) in the greenhouse using artificial FOV4 inoculation.

During the growing season, plant responses to fungus-inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor. In Upland cotton, germplasm with good levels of tolerance have been identified, and new breeding lines are being developed by USDA-ARS and the University of California. After FOV4 artificial-greenhouse and natural-infested FOV4 evaluations of these accessions, less than 0.1% were selected to develop highly resistant FOV4 progeny. Two sources (NM12Y1004 – NM12Y1005 and SA-3208) of Asiatic breeding origin were identified with tolerance to FOV4 and used to introgress and increase resistance. Pedigree information from additional parental lines or breeding stocks used to develop progeny revealed their sources to be exotic and wild Upland germplasm – triple/multiple crosses, deriving these SA-obsolete cultivars named ‘Auburn M’, ‘DES 920’, ‘MARSPD202085’, ‘S.N.0503-1’, PD 2165, and ‘Stoneville 14’, among others.

In 2019, around 130 selected breeding lines were ginned, acid delinted, and planted at two infested field sites in California [Los Palos (Figure 2) and Tipton Co. (Figure 3)] to validate their resistance/tolerance against FOV4.

Figure 2. Infested Fusarium wilt race 4 (FOV4) field site around Dos Palos, CA. planted with selected breeding lines to validate their tolerance level before public releases. Photos showing Dr. Ulloa next to one of the FOV4 highly resistant Upland lines surrounded by empty research plots from a susceptible FOV4 variety-check.

These selected lines were also planted at the Tipton FOV4 infested site (Figure 3). In addition, evaluations were performed on more than 500 additional Pima and Upland cotton lines from progeny and breeding lines with different levels of FOV4 tolerance/resistance. Most of these lines were derived from multi-cross-combinations between and within Pima and Upland cultivars or germplasm lines with known FOV4 resistance to develop progeny and new populations to assess FOV4 resistance.

Figure 3. Infested Fusarium wilt race 4 (FOV4) field site around Tipton, CA. planted with selected breeding lines to validate their FOV4 resistance/tolerance level before public releases, with an additional 500 Pima and Upland entries. Photos showing evaluation site and roots with no vascular root staining, a typical diagnostic infection sign of FOV4.

In addition, a subset of these entries was also planted in the El Paso, TX area in FOV4 infested field (Figure 4).  Following are images from the FOV4 infested field site near El Paso, TX.  We planted lines with known levels of FOV4 tolerance, and resistant and susceptible FOV4 check-cultivars using a RCBD with three replications (Figures 1-3).

Continuing with the breeding efforts of this cooperative project next year, we anticipate additional visits to California by Dr. Ulloa to coordinate and support the selection, harvest, ginning of breeding lines with good to excellent FOV4 tolerance/resistance for the 2020 year’s season.

Figure 4. Infested Fusarium wilt race 4 (FOV4) field site around El Paso, TX area planted with selected breeding lines to validate their tolerance level before public releases.

 

Management of Key Cotton Arthropod Pests with Insecticides and Acaricides

Objectives of Research

1.) Develop an expanded database on the current efficacy of labeled/recommended insecticide and acaricide products on key insect and mite pests of cotton in the San Joaquin Valley and document the influence of these products on beneficial arthropods with the objective of providing better guidelines on pesticide use.

2.) Evaluate the effectiveness of new candidate insecticide/acaricide products on key San Joaquin Valley cotton pests, the impact of these new compounds on populations of beneficial arthropods, and devise strategies for deploying these new products.

3.) Examine factors, including insecticide-related, environmental, and agronomic factors, which influence management of cotton arthropod pests with registered and experimental insecticides, emphasizing insects that threaten lint quality.

Introduction

We must maintain a multifaceted IPM approach to sustain an efficient and stable system of pest management in California cotton and to improve overall profitability. Insecticides remain a key component of effective management of arthropod pests in cotton. Furthermore, management of insect pests is a critical aspect of managing sticky cotton. California has a reputation for producing high-quality cotton, and successfully managing whiteflies and aphids and the resulting havoc they can create with lint quality is key to maintaining this reputation. Up-to-date data on insecticide efficacy are in constant demand by growers and PCAs, as are data on how given insecticides can fit within an IPM program. The results from this project will clearly be used nearly immediately.

Regulatory actions involving insecticides are ongoing and likely inevitable in California’s agricultural sector, which can lead to uncertainty and changes to what tools are available to control arthropod pests. In recent years, several insecticides, such as several organophosphates, Temik®, and endosulfan, have been lost due to marketing decisions (probably hastened by regulations). Use of several EC formulations in cotton have been limited due to VOC regulations in the SJV – dimethoate, abamectin, etc. Concerns about off-site movement (via water and air) have threatened registrations and use of chlorpyrifos and pyrethroid products (and several premixes that contain a pyrethoid). Belt® insecticide was removed from the market although it was promoted and thought to be a reduced-risk material for beet armyworm (and other species) control. Recently, numerous insecticides, especially neonicotinoid products, are being scrutinized due to the ongoing honeybee/pollinator concerns with proposed regulations potentially having significant impacts. There are a variety of neonicotinoid products used by the industry that could be influenced by future regulations. Registrations of “new” insecticide products such as Transform® are threatened and have been delayed (on again and off again) as well due to the pollinator issue. Transform will not be available for the upcoming season in California. During the last growing season, chlorpyrifos was slated from removal from the marketplace. This has clearly left a gap in tools for late-season management of aphids and whiteflies. The overall effect of the losses or lack of registrations is very problematic and makes pest management more challenging.

Products are also being removed from the “toolbox” because of the build-up of insecticide resistance in pests, which are constantly evolving. Organophosphates are typically not useful for lygus management, and pyrethroid insecticides may be useful for lygus for one application per season due to resistance. Spider mite control options have been available and numerous, but there appears to be some slippage in performance in recent years in other field crops. Given the ability of spider mites to develop resistance in multiple regions and cropping systems, this is not a surprise. Presently, whitefly control options are still in place although during some “application windows” there are now a shortage of options. Mid-season aphid management is still viable as long as the neonicotinoid products are available, but late-season there is a critical void with the loss of chlorpyrifos. Maintaining effective aphid and whitefly IPM programs is essential to addressing the threat of sticky cotton to the industry.

The challenges from development of insecticide resistance and regulatory actions are best addressed with well-planned research and interaction/collaboration with all concerned industry representatives. Fortunately, new materials are developed to facilitate IPM programs. These new products must be evaluated under California conditions. This development of new products appears to have slowed somewhat recently with the consolidation of the agrichemical industry and changes in ownership that have disrupted and delayed research plans. In the interim, available experimental products will be evaluated, registered products will be researched and evaluated for efficacy, and other IPM tactics will be studied and developed. This research has allowed and will continue to allow a thorough evaluation of the applicability of experimental materials for the California cotton system before they appear on the market. By examining the complete “big picture” of California cotton IPM, this project helps to determine the applicability and fit of these products. The pests of interest in this project include cotton aphids, spider mites, thrips, whiteflies, lepidopteran larvae, and lygus bugs. Emerging and invasive pests will also be addressed, as needed and relevant. The integration of insecticides and acaricides with other management approaches (biological control, etc.) will be emphasized.

Summary: Insecticide/Acaricide Efficacy

The research season in 2019 progressed well, despite some weather challenges early in the season that made research challenging when trying to get cotton planted, although this was something that commercial growers faced as well. Late-season rains prevented us from getting out cotton planted “on time”, especially at the Shafter Research Station. Planting at West Side Rec was less affected. Whitefly populations were low but were relatively consistent over the course of the trial. Our aphid populations steadily declined after the first application, leading to very low populations after the second application. In the past year, we continued conducting the research trials at the locations (West Side REC and Shafter Research Station) where they have been conducted for the past several years. Field and laboratory work was split between both locations, with the lygus and mite trials conducted at West Side REC and the aphid/whitefly study at Shafter Research Station.

Lygus

Objective: To evaluate Lygus bug management tactics, including newly registered insecticides, combinations of materials and varied timings, and industry standard (registered) insecticides, as well as the effect of treatments beneficial insects and secondary pest populations.

  • Application Dates:2 applications, July 9 and July 14
  • Study Location:West Side Research and Extension Center, Five Points, CA; Fresno County
  • Application Equipment: pull-behind tractor sprayer, CO2 propellant, Spraying Systems TX-VS10 nozzles (5 nozzles per row)
  • Application Parameters:20 GPA, 40 PSI, 3.5 MPH
  • Plot Size: 10 rows x 68′ feet, 4 replications
  • Plot Design: randomized complete block
  • Plot Condition:irrigated Acala cotton (PhytoGen 764 WideStrike RF) planted on 38 in rows
  • Insect Sampling: Lygus: Adults and nymphs per 50 sweeps per plot at various days after treatment (DAT). Secondary pests: 10 leaves/plot (5th main stem node leaf from top) were collected and aphids and spider mites counted in the lab 10 DAT1). Natural enemies were assessed once at 7 DAT1 using the same sweep net sampling used for lygus sampling. Later sampling using the same technique was not possible because of the growth habit of the cotton.
  • Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested.

For all results, see tables and figures for full analysis details and means.

Lygus nymphs: Pre-treatment populations of nymphs were 7.75 per 50 sweeps. At 2 DAT1, only Warrior and Vydate provided any level of control (70 and 76 percent). At 6 DAT1 Vydate provided 80 percent control, while both Transform treatments, Carbine, and Diamond+Carbine all provided 70-80 percent control. Differences were more pronounced 10 DAT1, with the same treatments (other than Transform-L) providing 80-90 percent control. Only Vydate had high levels of control 13 DAT1.

At 2 DAT2, a number of treatments had 80-90 percent control. At 6DAT2, Diamond+Carbine, Orthene, Transform (L and H) and Vydate all had 90-100 percent control. Diamond alone provided 80 percent. At 10 DAT2, only Orthene and Vydate had above 80 percent (83) control. The pattern was similar 13 DAT2 and at 21 DAT2, Diamond provided 90 percent control, Orthene 97 percent, and all remaining 51 percent and lower.

Lygus adults: At the first sampling (2 DAT1), Transform-L and Vydate provided a degree of control (70 and 80 percent). At 6 DAT2, only Transform-L provided any degree of control (75 percent). At 10 DAT2, many of the materials provided some degree of control in the 40-50 percent range, and Carbine, Diamond, Transform-H, and Warrior all provided 64 to 68 percent control. At 13 DAT1, Transform-H provided the best level of control (70 percent), with some control (54 and 59 percent) still offered by Carbine and Diamond+Carbine. 2 DAT2 Orthene provided 86 percent control. At 6 DAT2, both Transform rates provide 88 percent control. At 10 DAT2, a number of materials provide 45-60 percent control.

Natural enemies: We have not yet attempted to analyze the natural enemy data using multivariate statistics, so we present analysis of summed counts of natural enemies. At 2 DAT1, there were significant differences among treatments based on the overall analysis, but none in pairwise comparisons (numerically lowest in Belay, highest in Diamond+Carbine). At 10 DAT1, natural enemies were least abundant in the Belay and Sivanto-High treatments and highest in the Brigade and Untreated. At 13 DAT1, natural enemy populations had increased across most treatments, with the untreated having the most, followed by Brigade and Baythroid. Orthene, Assail, and Belay all still had low natural enemy populations.

Secondary pests: Aphid and mite populations were low during this trial and none of the treatments led to very high levels. Populations of aphids did differ significantly between treatments (F14,42 = 2.67, P = 0.007). At 10 DAT1 when they were assessed, aphid populations were highest in the Brigade plots (~1 per leaf), followed by Baythroid, Vydate, and then the Untreated. The only significant differences were between Baythroid and Assail, the latter which had the fewest. Mites were extremely low overall, with no significant differences among treatments (F14,42 = 0.57, P = 0.87). After the second application (6 DAT2), the untreated had the most natural enemies, followed by Vydate. Orthene, Transform-ow, and Assail all had few natural enemies. These patterns generally persisted through the end of the study. At 13 DAT2, the untreated had by far the most natural enemies, followed by Warrior and the Admire/Carbine treatment.

Yield: Yield was highest in the Vydate treatment with 3,254 pounds seed cotton per acre. This was followed by Diamond+Carbine with 3,152, Carbine with 3,093, Transform-H with 3,090. Brigade had the lowest yield at 2,015, followed by Baythroid at 2,148.

Bioassays

Similar to previous years, we have continued to monitor insecticide resistance in lygus populations for key insecticides. This includes older materials like Vydate and Capture, and newer materials that have been increasingly relied upon for lygus management, Capture and Carbine. For Vydate and Capture, these assays consisted of exposure of insects to the material in insecticide coated plastic bags. The Carbine method relies on dipped green beans, while Transform uses floral foam soaked with a solution containing the insecticide.

The data are still being processed for these assays, but we can report on the number of assays that were completed. To mirror prior years, we conducted both early and late season assays. For the early season assays, we had four locations, with insects collected between May 31 and June 13. For the late season assays, we again attempted assays at four locations, but lygus were no abundant enough for the full complement of assays. At two of the locations, we could run all four materials. At one site, we only had enough for two materials, so we focused on Carbine and Transform. At the other, site, we were unable to collect enough lygus for assays.

Aphids and Whiteflies
Objective: To compare the efficacy of selected registered insecticides and
experimental materials against cotton aphids and whiteflies during the midand
late-season period in Pima cotton.

  • Application Dates: 28 August and 11 September – Insecticides – 21 treatments
  • Study Location: Shafter Research Station near Shafter, CA; Kern County
  • Application Equipment: High-clearance trailer spryer pulled with a tractor, CO2 propellant, Spraying Systems TX-VS6 nozzles (5 nozzles per row)
  • Application Parameters: 30 GPA, 40 PSI, 3 MPH
  • Plot Size: 5 rows x ~55′ feet, 4 replications, 38 in. rows
  • Plot Design: Randomized Complete Block
  • Plot Condition: irrigated Pima cotton (‘Phytogen 841 RF’)
  • Insect Sampling: All insect data were collected from 10-leaf samples (5th main stem node leaf down from terminal) per plot. Cotton aphids (Aphis gossypii) and whitefly nymphs Bemisia tabaci Biotype B, (formerly B. argentifolii): visually counted on leaves using a dissecting microscope. Data on WF nymphs were collected per entire leaf as well as per “quarter-sized” disk (between the main leaf veins; not reported here). This is the area that the treatment threshold is based upon. Whitefly adults: leaves were carefully examined and turned over in the field and adults counted.
  • Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested. We did not harvest any plots in the first block because vigor was extremely poor, and this would have not been useful yield data. Yield was very low overall.

For all results, see tables and figures for full analysis details and means.

Aphids: On the day of application, aphids averaged 116/leaf. At 2 DAT, The low rate of Transform was most effective (91 percent control), followed by Lorsban+Dibrom and the high rate of transform. At 7 DAT1, both Transform rates performed well, with 98 and 97 percent control of the high and low rates respectively. Lorsban and Sefina-Low both provided 89 to 90-percent control. At 13 DAT1, many of the treatments provided excellent levels of control (many over 90 percent 80 percent). This included all of the newer materials (Sefina, Sivanto, Transform, PQZ, Carbine; all rates) as well as Assail, Lorsban+Dibrom, and Knack. Meanwhile, by this point, Vydate, Lorsban, and Courier had increased numbers of aphids relative to the control (numerically, not significantly different). Immediately after the 2nd application (2 DAT2), the Lorsban+Dibrom had the fewest aphids. At 7 DAT2, aphid populations in the untreated had started to crash and were only 9 per leaf. The following sampling dates were somewhat less useful because of the low untreated numbers, with one exception being that these patterns showed which treatments otherwise maintained aphid populations (see Vydate in particular).

Whitefly nymphs: On the day of applications, whitefly nymph populations were low at 0.9/leaf. At 2 DAT1, only Knack provided >50 percent control at 56 percent. At 7 DAT1, a number of the other treatments began to provide some level of control, with Sivanto-Low provided the best at 83 percent, followed by Assail+Bifenture at 76 percent. A number of other treatments provided 60 to 70 percent control. At 13 DAT1, the untreated had fairly low numbers, so percent control was poor across treatments (other than Courier). At 2 DAT2, Sivanto-High provided the best control (82 percent), followed by Assail and Sefina-High.  Lorsban provided the least level of control at this time point. At 14 DAT2, Cormoran provided the most control, followed by Assail, Carbine (although this appears to aberrant), Sefina-Low and Assail+Bifenture. Across dates, Vydate and Admire Pro performed poorly, several times having more nymphs than the untreated.

Whitefly adults: Whitefly adult counts typically ranged between 1 and 2 per leaf in the untreated over the course of the study. There were only significant differences among treatments for several of the assessment dates (7 DAT1, 2 DAT2, and 21 DAT-2 – at α = 0.10). Posthoc comparisons did not indicate any significant differences except on 7 DAT1 when the untreated was significantly different from over half of the treatments.  No individual treatment appeared to stand out when viewed across dates.

Secondary pests: Spider mites were evaluated as a secondary pest that could be flared by treatments for aphids/whiteflies. Mite counts were very low over the course of the study. We therefore analyzed counts summed by plot across the entire study. There were not significant differences among treatments for these counts (F19,57 = 1.17, P = 0.31).

Yield: Measuring yield was not one of the key aspects of this study because we are focused on managing aphids and whiteflies because of the way they threaten quality of lint (via sticky cotton) rather than quantity of lint. We did not detect significant differences in yield quantity (F19,38 = 0.41, P = 0.97).

 

Evaluation Of Effectiveness Of Varying Rates and Application Methods Using Cotton Clean ™ Technology

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The purpose of this study was to evaluate the effectiveness of the Cotton Clean™ product when applied with various methods and at various rates. The results confirmed what our preliminary research indicated.  Generally, the study indicates that Cotton Clean™ shows significant benefit in reducing stickiness on cotton that is at a level of moderate to heavy levels of stickiness.  Where stickiness is light or nearly absent, Cotton Clean™ does not have any significant effect on reducing stickiness.  From these findings, one may conclude that where stickiness levels are very low to begin with, there may be insufficient food source (deposited insect sugar) for enzymatic sugar reduction through the use of Cotton Clean™.  Therefore, the stickiness of cotton with low levels of stickiness do not change with any degree of significance.  This is true statistically, as well as economically, as extremely low levels of stickiness generally cause no detectible difference in textile processing or quality of output.

Also, we determined cotton ginned at commercial gins where Cotton Clean™ was applied at time of ginning was significantly less sticky than cotton from the same farm that was ginned at a facility where no Cotton Clean™ was applied at time of ginning.

Introduction

Aphid and whitefly pests are well distributed throughout the San Joaquin Valley and in many other irrigated upland and pima cotton producing regions, particularly where arid conditions exist.  It is well documented that several species of these pests can deposit objectionable levels of sugars through their excreta which can make processing seed cotton (in ginning) and cotton lint (in carding and spinning) very difficult and time consuming if sugar deposits reach moderate to high levels.  Growers have used many methods and approaches in keeping sticky cotton producing pests to a manageable level, but there are instances where their efforts are ineffective in the avoidance of problematic stickiness levels.  When this occurs, gins and spinning mills have severe problems in handling cottons in this condition.

It is believed that if the deposited insect sugar was converted into a substance with little or no viscous properties at ginning or spinning operational temperatures, without harming the cotton fiber onto which it was deposited, then ginning and spinning processes would be improved and lint quality preserved.

In 2016 San Joaquin Valley Quality Cotton Growers Association began work to identify ways to combat the ill effects of sticky cotton beyond control of the insect source itself.  A biological agent was introduced on problematic seed cotton that had been plugging up stands at a roller ginning facility.  It was sprayed on seed cotton at the module feeder in an aqueous solution.  Cotton so treated did not exhibit problems with plug ups at the stands.  After that initial trial further study was conducted and it was determined that a more precise formulation could be developed to address Trehalulose and Melizitose even more effectively.  In 2017 Cotton Clean™ was developed in conjunction with the manufacturer and their principal dealer.  Cotton Clean was provided to 12 different growers for use in applying at harvest and 1 gin used the material applied at the module feeder.

Lint samples were collected from bales treated with Cotton Clean™ and those bales not treated with Cotton Clean™.  Those lint samples were tested using Thermodetector, Mini card, and Mesdan ConTest stickiness testing methods.  Most test data sets indicated reduced stickiness on samples treated with Cotton Clean™, while a few sets were more inconclusive.  Whether or not influential factors not recognized had impacted the results was unclear.  Some of those factors are the subject of this project proposal, including rates of application and methods of application.  What is known is that ginning personnel report anecdotally that there were no problems with gin stand plugging on cotton treated with Cotton Clean™, whereas, untreated cotton from the same field continued to exhibit plugging problems.

A better understanding of the proper rate of use of Cotton Clean™ and most effective method for application will help growers and ginners make the most of this contamination mitigation tool.

Methods and Materials

Plan of work:

  1. Identify sources of seed cotton to be included in the study. Growers and ginners in the San Joaquin Valley were contacted to participate as volunteers in the study.  In addition to commercial locations, research plots were used as a source of seed cotton.
    1. Cotton was collected from and ginned at:
      1. The Shafter Research Station – Farmers Co-Op Gin
      2. Armstead Ranch – Westhaven Cotton Gin
  • Woolf Farming – Huron Gin
  1. Errotabere Ranches – West Island Gin
  2. J. Polder Co. – West Island Gin
  1. Seed cotton samples (both Upland and Pima) were collected from the fields prior to harvest, identified and segregated so as to preserve identity for both test and control sample sets.
  2. Varying rates (25 to 90 bales per pound) of Cotton Clean™ were applied through picker moistener systems at time of harvest as well as varying rates applied at time of ginning.
  3. Lint samples were collected at the gins and transported to secure storage until fiber testing is conducted.
  4. Lint samples were tested for stickiness using Mesdan Contest instrumentation and recorded.
  5. Randomly selected lint samples were procured for testing at USDA ARS New Orleans for additional confirmation of results.
  6. Results were analyzed and reported.

Results

The results from this experiment generally support our hypothesis that Cotton Clean™ reduces the stickiness grades determined by the Mesdan Contest Cotton Quality Testing machine. The overall results from all stickiness levels of cotton in the experiment were slightly in favor of the sample group that had Cotton Clean™ applied. The average stickiness level of the fields without Cotton Clean™ applied during ginning was 102. The average stickiness level of the fields with Cotton Clean™ applied during ginning was 97. A difference of 5 points on the measurement system of the Mesdan Contest machine is insignificant. While it is noted that some field stickiness grade averages were higher with Cotton Clean™ applied than without, those only occurred in samples with low (<100 stickiness grade).

However, when fields with lower levels of stickiness (<100 stickiness grade) were removed from the averaging process, the result is dramatically different.  When only those fields with medium to heavy stickiness were considered, Cotton Clean™ applied at ginning reduced measured stickiness significantly, from 147 down to 97, a reduction of 34%.

In order to confirm validity of results measured by the Contest instrument, a random selection of samples from each field was sent to USDA-ARS in New Orleans for blind testing using the standard minicard stickiness test. The minicard test uses a different method of measurement to gauge stickiness levels than the Contest instrument, but has shown relatively good correlation of stickiness between the two measurement technologies.  That being said, due to the variability of stickiness among samples within a field the results may also illustrate some degree of variation. The measurements reported by USDA are None, Light, Medium, Heavy, and Very Heavy. In order to make relevant those designations to Contest values, we assigned values we believe to be consistent with similar levels of stickiness as measured by the Contest instrument.  None = 10, Light = 75, Medium = 125, Heavy = 200 and Very Heavy = 375.  We assigned a numeric value of 10 for None in order to present it graphically, but for all intents and purposes Contest levels of 0 and 10 are effectively indistinguishable.

The results by field for the samples without Cotton Clean™ applied during ginning were 4 fields were None, 10 fields were Light, and 1 field was Heavy. The results by field for the samples with Cotton Clean™ applied during ginning were 1 field was None and 14 fields were Light.  None of the samples treated with Cotton Clean™ measured above a Light designation. It should be noted that the minicard designations are subjective evaluations of the technician conducting the test.  The difference between Light and None in some instances can be almost indistinguishable.  Medium, Heavy, and Very Heavy designations tend to be much more pronounced.  So as indicated by the Chart 3, one can see that only where stickiness is more than Light, (in this case Heavy in field 18), can we see significant improvement with Cotton Clean™.  This is consistent with the results developed independently with the Contest instrument and so therefore, we conclude the independent results confirm one another.

CHART 3

Since only one commercial gin applied Cotton Clean™ uniformly on cotton of a large scale (>10,000 bales) we were only able to evaluate stickiness grades of cotton ginned commercially at one rate (80 bales ginned per pound of Cotton Clean™ applied).  At this rate stickiness grades averaged 32 versus an average of 58 for those bales ginned from the same farm but ginned at a ginning facility that did not use Cotton Clean™.  Even though all the stickiness levels in this instance were not considered heavily sticky, this large scale test from a farm producing > 10,000 bales indicated that stickiness grades were significantly reduced when Cotton Clean™ was applied at the time of ginning.

Conclusion

Cotton Clean™ shows significant benefit in reducing measured stickiness in instances where stickiness levels in the field are expected to be medium or moderate levels and above. Even when cotton stickiness levels are below moderate, proper application of Cotton Clean™ at manufacturers suggested rates at time of ginning shows significant reduction in measured stickiness.

Acknowledgements

This study could not have been conducted without the assistance and cooperation of many individuals and organizations.  We wish to thank all who contributed something to this effort, especially the following:  Armstead Ranch, California Cotton Ginners and Growers Association, California State University, Bakersfield, Errotabere Ranches, J. Polder Co., Stone Land Co., USDA ARS New Orleans, Westhaven Cotton Co., and Woolf Farming Co.

 

 

Assessment of Fusarium in SJV Cotton: Field Evaluation Support, Identification and Commercial Variety Screening Evaluations

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This project covers two primary purposes: 1) Conduct germplasm screening trials of commercially-available cultivars plus evaluations of experimental cultivars seed companies submit to us for FOV resistance evaluations.  In these evaluations, all entries in all University of CA variety trials (Acala/Upland, Upland Advanced Strains, Pima, Pima experimental cultivars, National Standards trials) are included, plus experimental entries submitted by seed company breeders. 2) Support field efforts to collect samples and evaluate fields to determine and characterize the race of Fusarium (race 4 or others) in SJV cotton fields when growers, seed company reps or consultants contact us for assistance with plant evaluations and fusarium race identification.

Prior and Current Work

Resistance Screening Work – Commercially Released Cultivars and Company Experimentals. This work has been directed toward identification of relative levels of resistance/susceptibility to race 4 FOV, including both indices of severity of disease impacts and survival under moderate to severe FOV race 4 pressure, with focus on evaluations of newer experimental and commercially-available cultivars. The two objectives mentioned above are at least somewhat related, as we conduct field trials to evaluate germplasm resistance to FOV, and we need to identify and access fields and cooperative growers if field screening trials are to be conducted.

Field evaluations in the resistance screening program each of the years of the trials have included:

  1. Commercially-available germplasm of Pima varieties included in our variety trials
  2. Commercially available germplasm of CA Upland and any remaining Acala varieties included in our variety trials,
  3. Experimental germplasm from company commercial development and improvement programs, plus
  4. Entries from cotton breeders at a variety of locations, including those from the RBTN tests done nationwide, plus efforts will be made to solicit entries from private company breeders working with Pima or hybrids (we have some funding through Cotton Incorporated CORE that helps cover some of the costs for the other agronomic evaluations (yield, fiber quality) for the Regional Breeder entries from U.S. public breeders – but the costs of the FOV race 4 screening work are not provided by that funding)

Field Sample Evaluations Work

Some support has been utilized to facilitate travel to field sites and allow us to be in the fields to physically do the visual surveys and collect samples, and to provide county and UC support for repeated trips to screening sites/fields as well as to grower fields where the Principal Investigator for this study gets requests for field evaluations to assess presence of Fusarium race 4.  Efforts beginning in 2002 and continuing through current efforts have been in repeated field visits to grower field sites, collection and evaluation of stem and hypocotyl samples for evidence of vascular staining, and AgDia test evaluations when growers/consultants make the request for Fusarium race identification.

The varieties tested include all commercial and public breeder entries in our variety trial program plus company/breeder submitted experimental cultivars. This screening effort is separate from, and in addition to, the work covered in a separate breeding program effort supported through cotton industry funding for a project entitled  “FOV race 4 Germplasm Development” that in recent years has been jointly funded by CA Cotton Alliance and CA Cotton Growers Association Research Funds. That project is a cooperative project with Dr. Mauricio Ulloa of USDA-ARS in Lubbock, Texas.  The cooperative work with Dr. Ulloa is somewhat different from the screening efforts supported by this proposal in that this project is more focused on maintaining: (a) support for FOV race 4 resistance screening for commercial entry commercial and experimental entries, plus entries from public breeders; and (b) some funds to continue support for field race 4 evaluations requested from growers, consultants and seed companies for which we need to purchase AgDia test kits and cover related other expenses.

Field Sample Evaluations

Since 2013, we have been using the AgDia company race 4 FOV quick test on root and lower stem samples in these field evaluations.  For some FOV race identification pathology work for samples when we request additional evaluations over and above what can be done using the AgDia quick tests, we are working with Dr. Maggie Ellis at CSU Fresno to determine local capabilities for identification of other races of FOV if that becomes necessary and useful. The funds from this proposal/project help provide funds to purchase the FOV-4 AgDia kits, which cost approximately $35 for each sample run (just for the supplies, not other lab costs or staff time).

Summary Report of 2018-19 Activities

For 2019, sites for field evaluations and sampling were located in 4 cotton producing San Joaquin Valley counties  (Fresno, Merced, Kings, Tulare Counties), with the most new confirmed sites located in Merced County. There were 27 fields visited and evaluated visually for FOV4 evaluation, and sampling for Fusarium race 4 done in 19 fields, and confirmations of FOV4 in 16 of the fields visited. Unless we see significant increases in different variants of FOV (race 4, others) in cotton, we expect a downward trend in requests for field visits to continue in the next years.

The number of requests for field evaluations compares with sampling in earlier years: (1) 2018—48 fields evaluated, with 37 confirmed as race 4 FOV; (2) 2017—66 fields evaluated; (3) 2016—89 fields evaluated; (4) 2015—89 fields were visited for in-field evaluations, with AgDia tests run on 47, and 21 positive determinations in tests for race 4.  These numbers most likely do not represent the full number of additional fields that could have been identified as race 4 FOV, as some fields were visited where samples were not collected due to lack of grower desire or approval to collect samples needed to provide an assessment.

Results 2019 – Field Resistance Screening Evaluations

Field varietal screens were planted and completed at both field screening sites at the time of this report, both in fields confirmed to be infested with FOV race 4.  The field tests were done only in a part of the field where a prior cotton crop showed consistent, significant plant losses due to FOV race 4 (greater than 50 percent mortality in susceptible Pima entries). An initial plant population count was done within 2 weeks after planting in plots at both sites, followed by plant survival counts done a minimum of two times during an evaluation period of 7 to 8 weeks after emergence of cultivars being tested for resistance at the Tulare County site and a Dos Palos area (Merced County) site.

In addition to plant survival percentages, we evaluated plants for root vascular staining, foliar damage index rating, and plant size / height and node counts as a measure of vigor. At both sites, major hand weeding efforts were required to keep weeds under control in these sites due to restricted use of herbicides necessitated by working with conventional cotton varieties.

The commercial varieties and company and RBTN program breeder experimental materials evaluated in our Commercial Entry and Company/RBTN Experimentals screening trials for 2019 are shown in the following figures in this report.  Average root vascular stain values for the TULARE COUNTY SITE are the only 2019 date summaries available and ready to share at the time of preparation of this report. Data analyses on the rest of the data sets are underway and will be made available to seed companies, breeders and industry partners in the fall.

The following tables (Figures 1-4) show the average Root vascular stain index ratings for all of the Pima and Upland cotton entries in the commercial screening trial for FOV-4 resistance conducted at the Tulare County site in 2019.  As with prior years, check varieties are included in the screen: more susceptible varieties such as DP-340 and DP-744 Pima, and some more highly resistant commercial Pima varieties such as Phy 888RF, Phy 841 RF, DP 348 RF, DP 359 RF and others). Also included in this screen are all varieties entered in the following variety trials for 2019:  CA Uplands/Acala trial, CA Uplands Advanced Strains trial, National Standards Uplands trial, Pima variety trial, and RBTN (Regional Breeder Testing Network) entries.

Other than the previously mentioned Pima cultivars with higher levels of FOV-4 resistance, there are a limited number of entries in this commercial screen that appear worth a follow-up evaluation as potential higher FOV-4 resistance varieties, including:  Group figure 1: FM 2398, ST 4550, PX 8504 Pima; Group figure 2: DGX 19014, BX 2037, FM 162; Group figure 3: Phy-60, Phy 64 through Phy 67; Group figure 4: Ark 1112-59, TAM LBB 15905, CSX 8308.

When data is compiled for the second trial location (which includes most commercial entries other than the RBTN program entries), there will also be an opportunity to determine consistency of resistance screen results for two sites.

                            Figure 2
                          Figure 1
                        Figure 3

 

 

 

 

                       Figure 4

 

 

 

 

 

 

Data Summaries for 2018

As examples of the full data sets that are provided each year as a result of this project, the following tables of this report show the summary averages for the Tipton area site (Tulare County) in 2018. Similar data will be developed and posted when 2019 results are completed.  These 2018 tables and those from prior year summaries are shown on the UC cotton web site at http://cottoninfo.ucdavis.edu . This information includes foliar Fusarium ratings, root vascular stain ratings, plant height and node number as indicators of vigor.  In coming weeks as data is processed, we will add the plant survival percentage for each entry, but it is not included in this summary.  Data shown are determined from five plants evaluated in each of three field replications per entry.  The tests include all entries in University of CA cotton variety trials, additional commercial germplasm (company selected varieties plus experimentals they submitted) plus entries from the Regional Public Breeders testing program (including check varieties, organized nationally by Dr. Ted Wallace of Mississippi).

Information to focus on in reviewing the tables as best indicators of overall responses to FOV-4 infection are: (a) root vascular stain index; and (b) survival percent at 7 weeks, since they indicate relative severity of infection and impacts on plant mortality (this data, as mentioned above, is not summarized and available at this time).

“Check” varieties that are moderately to highly susceptible include: Phy-725RF, DP-340 (moderate), while a quite tolerant check variety would be Phy-802RF.  The scale for Foliar FOV index and root vascular stain index ratings is 0 to 5, with 0 being no symptoms, 5 being severe (usually reserved for dead, near-dead plants).  Keep in mind that ratings are done at 7+ weeks post emergence, so they are done on plants surviving at the time of the rating, which in the most severely impacted  entries  can be some of the few survivor plants, with most others dead. It is recommended that the combination of lower vascular stain ratings as a relative indicator of disease severity in tested plants must be considered in combination with survival of the plants in order to assess relative levels of resistance.

 

Identification and Development of Cotton Germplasm and Potential Breeding Lines with Improved Fusarium Wilt Resistance, Fiber Quality and Yield

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Objectives of Research 

  1. Develop and expand the cotton progeny and breeding populations segregating for Fusarium wilt race 4 (FOV4) resistance. (efforts are roughly split between Upland/Acala types of cotton and Pima germplasm).

2. Evaluate resulting progeny, breeding lines, and germplasm for FOV resistance.

3. Utilizing selected materials, maintain seed supplies through progeny propagation and breeding population increases at field location(s) in California and in greenhouses as necessary for limited seed entries.

4. As selected germplasm are advanced, also conduct trials to evaluate growth characteristics and yield performance  (growth habit, growing season length requirements and yield performance) at West Side Research Center location

5. Identify breeding lines and germplasm with improved combinations of FOV race 4 resistance, fiber quality, and yield for release and availability to breeders and seed companies as appropriate.

 Planting tolerant/resistant varieties is an effective strategy to manage FOV4 damage and losses in cotton. Progress has been made by University of California and USDA, ARS, and the private companies from information and results generated by this and other FOV4 research projects funded through California cotton growers/producers.   Research efforts have identified and developed tolerant/resistant Pimas, as have made some progress in identifying improved FOV4 resistance in Upland cultivars.

Field evaluations have provided information for a number of generalizations: (1) most Pima cultivars show more severe symptoms and suffer higher levels of stunting and plant mortality from FOV4 than seen with most Uplands or non-Acala, and Acala cotton; (2) some moderate to highly-resistant commercial Pima cultivars have been identified from several seed companies and private breeders; and (3) several experimental Pima germplasm or breeding lines with moderate to high resistance to FOV4 have been identified, developed, and publicly released (SJ-FR01 to SJ-FR09) by the Univ. of California and USDA-ARS. These germplasm lines have helped to increase the genetic base for FOV4 resistance in Pima Cotton.

Since 2013, more than 4,000 entries and developed progeny have been evaluated in infested FOV4 fields and a portion (1/4) in the greenhouse using artificial FOV4 inoculation. Our primary objectives have been to identify/develop additional Pima cultivars, and evaluate and develop the Upland gene pool for improved FOV4 tolerant germplasm.  Efforts have included introducing a known FOV4 dominant gene that has shown resistance in Pima (e.g., Pima-S6) into Upland cultivars, as well as, introducing tolerant gene(s) from identified Upland tolerant lines from our research obtained from the USDA-ARS Cotton Germplasm Collection and University-breeding programs into elite or improved yield and fiber quality cotton lines.

For the breeding efforts, entries and progeny have been planted in naturally-infested FOV4 fields and seeded in 5-by-1 meter plots and replicated three times. During the growing season, plant responses to inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor. Selected cotton entries used as parents to make crosses and progeny developed from these parental entries (F1 populations) were also inoculated with FOV-4 and grown under greenhouse conditions for rating. In addition, resistant/tolerant varieties or germplasm may not express similar modes of inheritance of resistance when they are derived from different genetic backgrounds or are challenged by different Fusarium types or races of different geographic origin. The postulated pathogenicity or mode of infection mechanisms and the inheritance of Fusarium resistance significantly differ among races for cotton entries or lines. Previous reports indicated FOV4 resistance is associated with a complex allelic-recombination and duplicated marker-genes between cotton chromosomes 14 and 17. Genomic islands or regions on chromosomes 3, 6, 8, 11, and 25 have also been reported to be associated with allelic dosage for FOV-4 tolerance. Additional analyses revealed that cotton lines and progeny share resistance genes for plant defense against Fusarium races (1, 4, and 7).

In Upland cotton, germplasm with improved levels of FOV-4 tolerance have been identified, and new breeding lines are being developed by USDA-ARS and the University of California with the support of the CA Cotton Alliance and the CA Cotton Growers and Ginners Association.  From 2019, more than 150 Upland breeding lines are being evaluated to validate their higher FOV-4 levels of tolerance and to identify the best FOV-4 tolerant lines for releasing to the public and private researchers and breeders. In Figure 1, the evaluation of FOV-4 results and the progress of selection of a few breeding lines from 2016 to 2018 are compared with check lines with known level of FOV-4 resistance (Shorty-Upland, Pimas: PS7 and P3-39 susceptible and PS6 resistance).

In Pima cotton, Egyptian and Peruvian Pima or long staple cotton have been evaluated for relative levels of FOV-4 resistance.  A half-dozen of these lines were selected to make crosses and develop progeny that eventually will derive new and more diverse Pima germplasm resistance to FOV4. From 2019, more than 300 Pima variants (Gossypium barbadense L.) from the country of Uzbekistan are being evaluated to identify new sources of FOV4 resistance for developing novel germplasm.

Figure 1. Average Root Vascular Wilt Staining values (VRS) of select germplasm. Examples shown are evaluations from 2016 to 2018 selections of selected entries or Parents (1-9) to be used in crosses to develop new progeny/breeding lines with improved Fusarium wilt race 4 (FOV4) tolerance (rating of vascular root staining (VRS) – scale 0 = no infection to 4 highly infected root with VRS or almost death).

Significance of Research

Fusarium wilt [Fusarium oxysporum f. sp. vasinfectum Atk. Syn & Hans (FOV)] of cotton (Gossypium spp.) in California has long been considered a serious fungal disease for cotton.  Some races of this disease were first noted in 1959 in California (Garber and Paxman, 1963), and the number of infested sites remained relatively limited until the mid-1970’s. Before 2003, FOV in California was thought to be primarily caused by race 1. Race 1 of FOV is typically found in sandy soils, with the most severe, economic impacts found when the disease organism is present in an interaction with root-knot nematodes (Bell, 1984; Veech, 1984). Susceptibility to FOV, particularly race 1 FOV is increased by the effect of the nematode’s wounds (Garber et al., 1979).  In 2003, UC Davis scientists (Kim et al., 2005) identified a race 4 isolate of FOV in California soils. Race 4 of FOV was first identified in India on Asiatic cottons and was not previously identified as a problem in the U.S. Recent field investigations (Kim et al., 2005; Ulloa et al., 2006) have found race 4 FOV in clay loam and loam soils, in which root knot nematode populations and root damage symptoms were largely absent.

The introduction of new genetic variability or genetic diversity into elite cotton germplasm is difficult and the breeding process slow. When breeders use new and exotic germplasm sources, which possess resistance disease genes, to introduce genetic variability, large blocks of undesirable genes are also introgressed during the recombination between the two parental lines (linkage drag). This linkage drag has limited the use of such germplasm. In terms of the maintenance of elite germplasm with elite genes/traits, very high constraints are placed on today’s cotton breeders. However, the competitiveness of the cotton industry will be dependent upon continuing improvements of traits such disease resistance, fiber quality, and yield.  We feel that improvements in host-plant resistance currently is the most economic and effective strategy for managing Fusarium Race 4 for continuing cotton production in the San Joaquin Valley region of California. Continuing the development of resistant cultivars or germplasm to FOV is important for reducing yield losses and reducing further expansion of the pathogen.

The primary areas of work in this project include the following:

  1. Maintain and further develop access to one (preferably two) field test sites infested with race 4 FOV as well as greenhouse space to continue resistant germplasm testing in the San Joaquin Valley.
  2. Using field and greenhouse screening sites available to us, test cotton progeny and breeding lines and continue making crosses with potential for improved FOV-4 resistance. Collect seed from self and open pollinated cultivars of interest/improved FOV-4 resistance or other traits, delint and prepare seed for plantings for further FOV-4 testing of segregating populations and for seed increases necessary to allow further agronomic testing for yield and quality, plus to provide seed for interested breeders for further development.
  3. A link to ongoing plant genetics program in FOV resistance of Dr. Ulloa and his continuing molecular work is a vital part of this project plan. Identification of developed breeding lines and germplasm with improved FOV resistance through molecular breeding increases the need for molecular markers because molecular markers facilitate selection of resistant cottons, and decrease cost, time, and the risk associated with subjective greenhouse or field phenotypic evaluations. Molecular markers can also help in the identification of the genes that provide host-plant resistance against FOV.
  4. Under current arrangements with USDA-ARS cooperators, one additional major part of the project is to produce, maintain and expand seed supplies for advancing germplasm. Work to be done includes seed preparation, progeny propagation and breeding population increases at field and greenhouse location(s) in California.

Progress on Objectives

  • A series of 4 to 9 Pima lines were grown for seed increase with intention of release as improved “SJ” series lines from program efforts since 2014. These lines are meant to have superior FOV resistance with the capacity to be used as germplasm in breeding programs.  Bolls of each line were harvested and have been evaluated for fiber quality parameters.
  • An additional 50+ lines were selected from other populations the past two years, as well as an additional dozen or more selections made from those with superior FOV resistance and fiber quality.
  • During the 2017 and 2018 seasons, more than 160 additional Upland entries/germplasm were evaluated under a FOV race 4 infested field in California. These entries represent a wide range and diverse genetic backgrounds of germplasm material or cotton types. We continue to follow our established breeding scheme or strategy for identifying, selecting, and developing FOV race 4 resistant/tolerant germplasm. Selected breeding lines from 2013-2014 and now re-selected in 2015 through 2018 have been examined and targeted for the introgression of FOV race 4 resistance/tolerance genes from entries such as Pima-S6 (PS-6), Upland TM-1, and Acala FBCX2, an original pedigree-parental line of Acala NemX. So far from this set of derived progeny, around 20 breeding lines continue to show FOV race 4 resistance-improvement, and about 12 to 15 lines were re-selected in a seriously infested field this and last season. In addition, we continue to search for new sources of FOV race 4 resistance/tolerance within the Upland germplasm gene-pool by evaluation of around 150 added entries in each of the past several years.
  • In 2018, 2017 and 2016, as in prior years, over 100 newly tested genetic-diverse Upland and some Pima entries/germplasm were evaluated for FOV race 4 tolerance. These entries were also received from screening and selection efforts at the USDA-ARS, PSGD Laboratory, Lubbock, TX. From this set of entries, about two dozen additional cultivars were identified with good levels of FOV race 4 tolerance. Selected entries were self-pollinated for seed increase and further testing, and entries were evaluated in fields for FOV resistance and other desirable plant characteristics in field trial sites in 2018.  Similar efforts are underway from 2019.

Evaluation of Inoculation and Screening Strategies in the Greenhouse and Field

Grain carriers (wheat, rye ) were inoculated with FOV race 4 and added to the soil in whole grain and ground form to the soil at both of our field FOV-4 screening sites (Tulare County and Kern County) to supplement existing FOV-4 inoculum and assess the feasibility of using with these substrates as potential methods of inoculation compared to the current standard of liquid conidial inoculation used in our greenhouse inoculation and screening trials.  We utilized rye grain in 2017 and 2018 field  trials due to what appeared to be superior inoculum development compared with other tested grains.

Dr. Maggie Ellis of CA State University Fresno has worked on some seed inoculation in growth chamber settings, with FOV-4 seedling evaluations done at intervals after pathogen exposure.  The approach could be helpful as an alternative quick-screening method alternative to the root dip method we have been using in the UC Kearney REC greenhouse.  We have worked with her graduate student (Josue Diaz) and Dr. Ellis in field assessments and greenhouse assessments, and feel that there will be value in combining some of these early screening approaches with field assessments for more complete cultivar disease resistance evaluations. With that in mind, there is evidence to suggest that  rolled towel methods may be useful as a reliable pre-screening test to identify materials that are so susceptible that field screens are unnecessary; and additional work is needed to identify a reliable severe test that could be replicated as a follow-up/critical test to further verify the best-performing cultivars/germplasm identified in field screening tests (both could be very useful in breeding programs.)

Developing a Broad Germplasm Base of Populations for Future Selection of Material With Advanced FOV Resistance and Good Fiber Quality

As materials are developed for which we require seed production as well as more advanced agronomic testing for yield or fiber quality, fields have been set up at UC West Side REC for seed increase needs, and screen materials developed for larger scale self pollination needs. As needed, we will develop new crosses for promising materials, and continue to utilize lines developed based on crosses made in the past few years in order to provide not only resistant Pima materials but also develop some Upland / Acala FOV-4 resistant/tolerant materials.

In all evaluations of responses of cultivars to FOV race 4 pressure, rating procedures are standardized across sites and experiments.  Measured responses to FOV will include percent plant survival and standardized ratings of disease severity and vascular discoloration.  Vascular discoloration of the lower stem and upper tap root are observed by slicing the stem longitudinally, and rated according to the scale of 0) no symptoms, 1) light staining as spotty areas, 2) light colored staining, continuous and covering ¼–½ of the stem diameter, 3) moderate brown or black staining in a band encircling most of stem cross section, 4) brown or black staining  across most vascular tissue in cross section, and 5) dark brown or black staining accompanied by plant death.

A very large-scale effort for seed production was made in 2018 on about 1 acre of tented or bagged plants (to prevent bee pollination), with a much smaller (about 1/4 acre) similar tented planting for seed increases done also at West Side REC in 2019.   The photos shown below were taken in August, 2018, and show an approximately two acre area with about 1 acre of planted rows (split into two fields) where we grew out some selections and crosses that we determined to have improved FOV-4 resistance (as determined in multiple field disease resistance screenings).  For 2018, there were about 600 bagged or “tented” plots in these two fields at the UC West Side REC, representing close to 400 different entries for which we grew out plants to be self-pollinated to increase seed amounts for continuing work, and in many cases, to provide seed for additional testing and release to breeders.   The purpose of the” bee-proof” netting used in the tenting and bags is to prevent insects from cross pollinating the cotton that we want to be self-pollinated for seed increase/production.

“Bee-proof” netting used in the tenting and bags helps prevent insects from cross pollinating the cotton that researchers want to be self-pollinated for seed increase/production. (Photo courtesy of B.Hutmacher)

As examples of the work being done on several fronts (Pima, Upland, crosses), in field trials done in heavily FOV4 infested fields, we evaluated lines, crosses and some reselections based on current and prior year screening efforts, with the following examples of some cultivars being advanced in the testing program:

  • Egyptian source Pima entries: Three entries selected for advancement based on very good FOV vascular stain ratings.
  • Crosses made in 2015 and 2016 (Pima x Upland crosses): 31 entries advanced in selection for seed increase based on very good FOV vascular stain ratings.
  • New Entries from Upland Program and Collection of Mauricio Ulloa for 2017: 17 entries advanced in selection for seed increase based on good to very good FOV stain ratings.
  • Experiment #9 (based on 2015 and 2016 Pima selections tested for FOV-4 tolerance at Tulare County site): 10 entries advances in selection for seed increase and further testing based on good FOV stain ratings and agronomic characteristics – tested multiple years and sites.
  • Experiment #10 (based on 2015 Upland selections tested for FOV-4 tolerance at Tulare County site): 5 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.
  • Experiment # 11 (F-2’s based on 2014 Crosses at Tulare Co. site (some Upland and Upland-by-Pima included) followed by reselections in Greenhouse evaluations: 22 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.
  • Experiment #12 (both Upland and Upland by Pima crosses at Tulare County site): 17 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.

Verticillium Wilt Resistance of Newer Germplasm in Pima, Acala and California Upland Varieties

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The overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide location(s) for field screening of cotton germplasm of interest in CA Cotton production.  The aim of the work will be: (1) to sustain a relatively small location (approximately 0.5-1 acres) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for California cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative Verticillium wilt levels in cultivars being tested in the FOV race 4 screening location(s).

Some of the evaluations have either not been done (West Side REC) for 2019 or have not yet been summarized (Tulare County site) at the time of preparation of this report since the best time for evaluations of this type are generally mid- to late-summer. Results from the 2019 field evaluations will be summarized when data is available.

Summary from 2018

Tulare County Location:

All entries grown in the FOV race 4 screening trials were grown at a location with Verticillium present, which also turned out to be a location that had race 4 FOV present.   The screening for Verticillium was still done at this location since the plantings were in place and we considered it to be useful information, and the Verticillium screening was done on a minimum of 5 plants per entry per replication, for a total of 15 plants per entry to rate for incidence (of plants with Verticillium evidence in the stem – vascular staining about 1/4 to 1/3 of the way up the stem, as compared to root vascular staining evaluations for FOV).

West Side REC location:

Evaluations were done at a site at the West Side REC of the University of CA where we planted small plots for evaluation. The screening for Verticillium was done at this location on 7 plants per entry per replication, for a total of 21 plants per entry to rate for incidence (number of plants with Verticillium evidence in the stem – vascular staining about 1/4  of the way up the stem, as compared to root vascular staining evaluations for FOV).

The overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide a location for field screening of cotton germplasm of interest in CA Cotton production.  The aim of the work will be: (1) to sustain a relatively small location (approximately 1 acre in multiple variety trials) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for CA Cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative Verticillium wilt levels in cultivars being tested in the FOV race 4 screening locations.

The intent of continuing this work on a relatively small scale, and with data reported from both West Side REC and field trial locations where we also are doing Fusarium race 4 field screening is to develop information on Verticillium wilt incidence in currently-grown and possible future cultivars of interest for California cotton production.  Verticillium wilt incidence was evaluated in 5 plants per field replication at each field site.  The intent is that UC and USDA-ARS investigators as well as seed company representatives and breeders could use this information in determining the relative need for follow-up evaluations and screening efforts for Verticillium wilt susceptibility as they advance cultivars through their selection processes. The charts attached to this brief report give an indication of the levels of Verticillium seen during the current year evaluations for the broad mix of cultivars.

Verticillium wilt incidence evaluations were done on a large collection of experimental Pimas and Uplands that were included in our Uplands Advanced Strains trial, plus experimentals submitted by seed company representatives or breeders, plus public breeder entries in the RBTN (Regional Breeder Testing Network) evaluations coordinated by Ted Wallace of Mississippi State University in cooperation with the USDA-ARS.  Figures 1 through 5 show Verticillium incidence in commercial Upland/Acala & advanced experimental Uplands at Tulare County site in 2018 field evaluations.   The five graphs show data for over 100 entries plus three check varieties.  The check varieties were evaluated for consistency of data across field replications, and generally incidence of verticillium was evident across all three field replications in most entries.   Check varieties included were:  DP-340 Pima, Phy-888RF Pima and Mon-109-C7 Experimental Pima.

Data for the Tulare County site and the West Side REC site for 2018, and similar
results will be prepared when 2019 data is available on the UC Cotton Website.
Verticillium incidence is generally higher in Upland varieties than in Pima varieties. However, there are examples of very low incidence, or even zero incidence cultivars in both Upland and Pima data particularly at the Univ CA West Side REC site, but in some cases
also at this one Tulare County site. It was interesting that the experimental
Egyptian Pima cultivars worked with in recent years and in crosses did not
appear to be susceptible to Verticillium, at least at 2018 evaluation sites. Similar
data will be collected from two sites in 2019 and made available after analysis.

The intent of this work is to provide it to seed companies as a means of identifying materials that may require some additional evaluations for Verticillium susceptibility as they move forward in their breeding programs.

Pima On-Farm Variety Trials, Pima Research Center Variety Trials

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Project Summary

Field evaluations of Pima cotton varieties will be conducted at a UCCE Research Center location (West Side Research and Extension Center) and at 3 grower field sites as follows:

  1. For 2019, we conducted trials at the UC West Side REC and 3 grower field farm sites. Sites are located in Kings County, Kern County, and Merced County); and
  2. For 2018, we conducted Pima variety trials at the West Side REC, Fresno, Merced and Kings County grower sites; and
  3. We offered the opportunity to conduct smaller-scale research plot variety trials of Pima varieties at the West Side REC, including any experimental varieties supplied by seed companies where seed quantity available for testing is limited.

Preliminary Summary of 2019 Year

2019 Trial Activities:

Entries included in the field trials for 2019 included the following cultivars planted at West Side REC and Farm locations. Results of trials each year will be available at the same UC cotton web site mentioned for prior year results.

Entries Planted in 2019 Pima Variety Trials – West Side REC: DP 341 RF, DP 348 RF, Phy PX 8504RF, DP 359 RF, PHY 841 RF, PHY 881 RF, PHY 888 RF, HA 1432, PHY 802 RF, and PHY 805 RF.

HA 1432 was also planted at a Merced Co site.  Phy-802 RF and Phy-805RF were only at WSREC.

Entries planted at the grower sites will be reported by individual sites.  There were differences in the entry list due to expressed grower interest and willingness to have plantings, and some differences due to limited seed availability.   Complete list of plot maps at each site can be available on request.  For the most part, the varieties planted were the same as at WSREC, except for some sites that did not want the Hazera hybrid, which is non-transgenic and not glyphosate herbicide resistant.

Research Center and Farm Trial Sites: West Side REC, Kern County – Bone Farms, Merced County – Bowles Farms, Kings County – Hansen Ranches. In addition, all of the entries in these trials were included in our field Fusarium race 4 screening trials for 2019 as in all prior years. A selection of Pima varieties from Egyptian sources were planted at a Merced County site for evaluations in including yield potential, earliness and FOV-4 resistance, and if possible, fiber quality samples will be collected for hvi evaluations.

Results from those trials will be summarized and reported in our final screening information after completion of field data and analyses.  The results will be available on the University of CA cotton web site at http://cottoninfo.ucdavis.edu

The 2019 field trials were still underway at the time of this report, so there are no yield results or other hvi results from 2019 trials available.  The 2018 results from Pima variety trials are available on the web site mentioned.

Upland and Acala Research Center Variety Trials

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Acala and Upland acreage continues to be far less than Pima plantings in this and recent years. There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lower-risk decisions.   All of the entries in both types of trials were harvested in late October or in November by spindle picker (center two rows harvested out of four row wide plots). Subsamples from all field replications of the trials at both sites will be collected, and will be ginned starting in early December on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions. Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, Calif.

2019 Trial Activities:

Entries included in the field trials included the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at UC cotton web site mentioned for prior year results.

Entries planted in 2019 UC / Cotton Inc. / CCGGA Research Funded Acala / Upland Variety Trials – West Side REC location only for 2019: FM 1830GLT, ST 4550GLTP, FM 2398GLTP, ST 5600B2XF, ST 5707B2XF, FM 2498GLT, ST 5471GLTP, FM 2574 GLT, PHY 764WRF, DP 1646B2XF, DP 1820 B3XF, and DP 1845B3XF.

Entries Planted in 2019 CA Upland Advanced Strains Variety Evaluations – West Side location: Phy-764 WRF (check), DGX 19001 B3XF , DGX 19014 B3XF, DGX H929 B3XF, BX 2002 GL, BX 2005 GLT, BX 2037 GLT, BX 2016 GLTP, BX 2022 GLTP, BX 2076 GLTP, BX 2398 GLTP, FM 2498 GLT, ST 5600 B2XF, ST 5707 B2XF, FM 1621 GL, 18 R411 B3XF, 18 R421 B3XF, 18 R423 B3XF, 18 R438 B3XF, 18 R445 B3XF, 18 R448, and B3XF.

Entries Planted in 2019 Western and National Entries–NATIONAL STANDARDS TRIALS  – West Side REC location: DP 1646 B2XF, NG 4545 B2XF, PHY 764 WRF, PHY 499 WRF, DAYTONA RF, DP 1549 B2XF , FM 1830 GLT , FM 2574, and DP 1522 B2XF.

Entries Planted in 2019 RBTN (Regional Breeder Testing Network) Program–West Side REC location LA16063019, LA16063033, LA16063054, 13AFX6-27-2, 13AFX13-12-5, Ark 1115-36, Ark 1102-55, Ark 1114-21, Ark 1117-60, Ark 1124-50, Ark 1112-59, TAM 13S-03, TAM 12J-39, TAMLBB15905, TAMLBB16507, GA2016024, GA 2016099, GA 2016103, MS 2010-87-37, CSX 8308, DP 393 check, DP 493 check, FM 958 Check, UA 222 check.

All of the entries in these trials were included in our field Fusarium race 4 screening trials for 2019 at one location. Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu.  The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and Shafter (for primary Upland/Acala trial) for 2019 focused mostly on yield performance, gin turnout, and fiber quality components.   This information will be available following the conclusion of the growing season, and data presentation will be via the UC cotton website, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office.

2018 Project Summary
The overall project supports in part conducting three types of variety trials:

a. Testing of commercial non-Acala Upland varieties (and remaining Acala types if      available), with a target of two sites (one on-farm site or Shafter Research Station site in Kern County if possible, plus the University of CA West Side REC for these trials); and

b. Small scale testing at the UC West Side REC of a range of Upland varieties that are either only available in small seed quantities or that are experimental or of limited current commercial interest for grower field trials (CA Upland Advanced Strains Trials)

c. Small scale testing at the UC West Side REC of entries in the National Standards and Western Regional trials in a small plot, four replication trial at this one site.

For 2018, the set of trials planted were:

d. Acala and non-Acala Upland varieties to bed grown in two sites including a plot trial at the University of CA West Side REC in Fresno County and the former UC/USDA field station site in Shafter, CA in Kern County; plus

e. A small plot trial with limited seed availability CA Upland cultivars (or entries of limited or unknown commercial interest for the San Joaquin Valley), with the plots established at the West Side Research and Extension Center.

f. Entries in the UPLAND COTTON Western Regional and National Standards trial coordinated by USDA-ARS, with entries supplied for western region by Alison Thompson, USDA-ARS, Maricopa, AZ on request of the national standards committee

This project, with partial support from Cotton Incorporated plus added support from the CA Cotton Ginners and Growers Association Research Fund and from participating seed companies for the Advanced Strains trial, is now the only public variety testing program for Upland/Acala varieties of potential interest for San Joaquin Valley cotton production.

The small plot trials have 4 replications, with plots 4 rows in width by 60 to 70 feet in length (depending upon seed availability and locations used for the trials).  The test sites at the West Side Research and Extension Center in Fresno County were planted the third week of April this year, and the Shafter site was planted in the third week of April this year.  The goals of the project are to provide trial sites for testing a large number of entries of potential interest to seed companies and growers, with entries chosen to assess relative performance in SJ Valley settings and areas where Uplands/Acalas have been of at least some continuing commercial interest.

Data Collection and Availability From Field Trials:

Summaries of prior year trial results are available at http://cottoninfo.ucdavis.edu). In addition, results are presented at the Cotton Workgroup meetings and at winter and spring grower/PCA meetings of the University of California.  Results of the trials will be reported in winter meetings of the UCCE Specialist and Farm Advisors, and will be available in a printable form (pdf or Word) as full tables on the University of California cotton web site: http://cottoninfo.ucdavis.edu

Field Work for 2018

Acala and Upland acreage continues to be far less than Pima plantings in this and recent years.  There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lower-risk decisions.

All of the entries in both types of trials were harvested in late October by spindle picker (center two rows harvested out of four row wide plots).  Subsamples from all field replications of the trials at both sites were collected, and will be ginned starting in November on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions.  Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, CA.

*If the services are available, we may try to run two replication subsamples per variety through the Shafter Research Gin, if it is in operation this year, in order to provide more reasonable gin turnout estimates.

2018 Trial Activities:

Entries included in the field trials include the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at the UC cotton web site mentioned for prior year results.

  • All of the field plots at the West Side REC yielded and looked relatively good, despite heavy early- to mid-season lygus pressure and the hottest July on record in the Fresno County and San Joaquin Valley area (with over 30 consecutive days with high temperatures in excess of 100 degrees F).  Some of the bottom crop was lost due to lygus pressure, with some losses also attributable to high nighttime temperatures
  • As with the past two years, we no longer have access to the Shafter Research Gin at the old Shafter Research Center, so the only gin turnout and lint percent data available are those derived using mini-gins, with no other cleaners other than hand removal of trash materials during the ginning process.

All of the entries in these trials were also included in our field Fusarium race 4 screening trials for 2018 at one location.  Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu

The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and on-farm trials focuses mostly on yield performance, gin turnout, and fiber quality components.   This information is available via the UC cotton website mentioned earlier, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office. Thank you for the past and current support of these trials.  If you have questions, please direct them to Bob Hutmacher at (559) 260-8957 or rbhutmacher@ucdavis.edu.

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