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.
3. Progress Report
The agreement was established in support of objectives 4b and 4c of the in-house project, the goal being to evaluate and validate yield, fiber quality, and disease resistance improvements of ARS in-house breeding lines through comparative field and greenhouse evaluations. Documentation of yield, fiber quality, and disease resistance improvements of cotton breeding lines are important to maintain the competitiveness of US cotton. Five advanced Upland and 10 Pima breeding lines with resistance to the causative agent of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) were evaluated for yield potential, fiber quality characteristics, and other agronomic traits at two field locations in California (University of California West Side Research and Extension Center; USDA, ARS Shafter Cotton Research Station). In addition, more than 5000 plants were assayed for resistance to races 1 and 4 of F. oxysporum f. sp. vasinfectum in a greenhouse at the University of California Kearney Agricultural Center, and in a field infested with F. oxysporum f.sp. vasinfectum in Kern County. Observed disease responses revealed interactions between cotton entries and different races of F. oxysporum f.sp. vasinfectum. Analyses of these data were initiated to investigate the inheritance and the discovery of a gene or genes involved in Fusarium wilt resistance. 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.