1a. Objectives (from AD-416):
1) Develop genetic resources and cropping practices that increase cotton water-use efficiency. 2) Develop new cotton genetic resources with improved fiber quality, lint yield stability, and adaptation. 3) Develop management techniques for cotton grown with conservation tillage after a winter biofuel crop.
1b. Approach (from AD-416):
Basic genomic and applied research will be conducted on improving cotton water use efficiency. In this research, molecular techniques will be used to search for genes that may provide more tolerance to water-deficit stress. Field studies will be conducted to screen cotton germplasm for water-deficit stress tolerance and to determine how agronomic practices affect plant water status. Contemporary plant breeding methods will be used to develop and release high yielding germplasm lines with improved fiber quality. Germplasm combining ability studies as well as studies determining genetic mechanisms for improved fiber quality will be conducted to accelerate the germplasm development program. We will evaluate cotton production potential when double cropped with winter crops harvested for biofuels. Winter crop biomass and energy content, cotton seedling establishment, and cotton fertility needs will be assessed.
3. Progress Report:
Gene Identification Research. An experiment was conducted to identify genes in cotton roots with expression sensitivity to water deficit stress. Out of nearly 34,000 genes assayed using next generation DNA sequencing techniques, our research identified more than 1,500 genes with expression sensitivity to water deficit stress. Both up-regulated and down-regulated genes were identified. Of particular interest, this research identified several aquaporin genes with expression patterns sensitive to water deficit stress. Overall, this research will help efforts to understand the complex responses governing gene expression regulatory mechanisms while also identifying a large number of useful candidate gene targets for the genetic improvement of water use efficiency in cotton. Genetic Improvement Research. Two experiments are currently being conducted with the ultimate goal of developing new cotton genetic resources with improved fiber quality, lint yield stability, and adaptation. The first experiment is evaluating the breeding combining ability of the high fiber quality and genetically diverse Pee Dee germplasm with cotton germplasm developed in numerous other US cotton production areas. Results indicate that recently developed elite Pee Dee germplasm lines combine well with other US cotton germplasm and offer breeding parents that break the negative linkage between fiber yield and quality. The second experiment is determining the genetic relationships between several germplasm sources of high fiber quality. An analysis of two years of field data suggests that these germplasm sources contain and transmit different genetic factors for high fiber quality that can be combined to further improve fiber quality. A set of experimental breeding lines derived from both genetic studies are being evaluated in replicated breeding trials for their potential germplasm release. These new breeding lines offer new genetic resources that can be used to develop new cotton cultivars. Cropping Systems Research. Winter cover crops are commonly grown to enhance cotton productivity when cotton is managed with conservation tillage in the southeast. A two year study was conducted to investigate cotton productivity following harvest of the winter crop biomass in a winter-biofuel crop/cotton double cropping system. In the study, four cotton lines with diverse genetic backgrounds were grown. Preliminary analysis indicates removal of the winter crop biomass does not negatively affect cotton productivity in this system. Also, the four cotton lines had similar yield suggesting that criteria growers use for cultivar selection in this system does not need to be modified.
1. Identifying cotton breeding parents that break the negative relationship between fiber yield and quality. Cotton breeding parents with broad breeding potential are needed to develop the next generation of high yielding, high quality cotton cultivars. In this study, we determined the breeding potential of newly developed, elite Pee Dee germplasm lines. Breeding families involving elite Pee Dee germplasm lines and germplasm lines from eight U.S. public cotton breeding programs were evaluated in replicated trials for their yield and fiber quality performance. Results determined that the breeding potential of elite Pee Dee germplasm lines was equal to or better than two well-known, commercial cultivars. In addition, results suggested that recently developed, elite Pee Dee germplasm can be used to generate breeding populations with a lessened or absent negative relationship between lint yield and fiber quality. The research is expected to improve cotton breeding efficiency by advancing the development of cultivars with the unique combination of both high fiber yield and quality.