1a. Objectives (from AD-416):
The objectives of this research are to evaluate and validate improvements within ARS in-house breeding lines in yield and fiber quality traits through comparative field evaluations, and to evaluate and identify sources of Fusarium wilt (FOV) resistance in a diverse cotton germplasm collection, including commercial and experimental cultivars and mapping populations, through field and greenhouse trials.
1b. Approach (from AD-416):
Acala, non-Acala Upland, Pima, and other Gossypium cultivars and germplasm from a broad genetic background will be evaluated for yield and fiber quality properties at both Shafter and West Side Research and Extension Centers of the University of California, and in commercial fields when available. In addition, for Fusarium wilt resistance (FOV), cotton entries will be evaluated at the University of California Kearney Research and Extension Center greenhouses, and in verified FOV race 4 or race 1 infested commercial fields when available. Completely randomized or randomized complete block designs with three or four replications will be used for most trials. A minimum of two replications will be used for yield or FOV resistance estimation when seed availability or study acreage is limited. Plot size in field studies will vary depending on objectives and seed and land availability. In studies focused on yield characters, data collected will include in- and end-of-season measurements of plant height, number and type of nodes, and boll position, retention, and numbers per plant. Fifty-boll and six-pound samples of seed cotton will be collected to estimate lint percentage and fiber quality properties. These cotton samples will be ginned at Shafter to determine lint percent. Where fiber quality is of key interest samples will be sent for analysis to one or more commercial classing laboratories or to the USDA Classing office in Visalia, CA. Studies focused on identification of FOV resistance will assess a diverse cotton germplasm collection, which includes diploid cottons, public germplasm, and germplasm developed by conventional breeding techniques. Measured responses specific to FOV studies will include stand survival rates, ratings of disease severity, and vascular staining. Results of FOV field trials will be supplemented by replicated studies under greenhouse conditions, which will document responses of cultivars or breeding lines to artificially-inoculated soil mixes. Several races of FOV (e.g., races 1 and 4) may be used in greenhouse evaluations to better understand variations in exhibited germplasm resistance responses. In addition, we will evaluate selected control practices such as seed treatment, planting date, and irrigation regimen under different soil types for management of the FOV disease in combination with resistant or tolerant cultivars. Documents NFCA with University of CA-Davis. Formerly 5303-21220-003-16N (11/10).
3. Progress Report:
The goal of this project is to evaluate and validate yield, fiber quality, and disease resistance improvements of ARS in-house breeding lines through comparative field and Fusarium wilt resistance greenhouse evaluations. In our continuing efforts to introgress the Fusarium wilt (FOV) race 4 resistance and to develop FOV race 4 resistant Upland germplasm, more than 500 plants were assayed for resistance to FOV race 4 in greenhouse and field studies. We also increased seed of the next generation of progeny developed from known resistant and susceptible cotton entries to FOV race 4. Seed of around 511 progeny-families was prepared for testing under infested field and greenhouse artificial FOV race 4 inoculation. Results from preliminary analyses to introgress Fov4 gene from resistant Pima-S6 into developed progeny revealed positive introgress. Some evaluated progeny showed as high as or higher resistance than Pima-S6 parent. Also, field and greenhouse evaluations identified Acala, non-Acala Upland and Pima varieties, landraces, and breeding elite germplasm with different levels of resistance. Efforts continue for the evaluation and possible release of five Pima breeding lines with resistance to FOV races 1 and 4. Upon release, these breeding lines will expand the genetic base cottons with FOV race 4 resistance. Continuous improvement of disease resistance, yield, and fiber quality of cotton breeding lines is important to maintain the competitiveness of U.S. cotton industry. Activities during this project were documented through presentations at meetings of cotton growers, professional societies, and commodity groups, and through telephone contacts and site visits with collaborators.