Location: Crop Genetics Research2014 Annual Report
1a. Objectives (from AD-416):
Objective 1 - Develop and release superior cotton germplasm or genetic stocks that incorporate improved lint yield, combined with value added traits such as longer fiber, improved ginning efficiency, nectariless, or high leaf Terpenoid Aldehydes, with accompanying DNA markers and improved methods for effective selection. Sub-objective 1A - Identify and evaluate lines with improved ginning efficiency using conventional and molecular methods. Sub-objective 1B - Identify and introgress into adapted cotton lines, natural variants that improve host plant resistance (HPR) to pests. Objective 2 - Use genetics, genomics, and molecular approaches to determine interrelationships among these genetic and agronomic traits and how they are controlled, as well as develop strategies to reduce undesirable linkages between traits. Sub-objective 2A – Broaden the genetic base of Upland cotton and improve efficiency of trait transfer by evaluating genetic and genomic relationships and the interactions that occur during intermating and introgression of fiber traits. Sub-objective 2B - Develop and compare strategies to reduce undesirable linkages between lint yield and fiber traits. Sub-objective 2C - Use the rapidly expanding arsenal of molecular techniques to develop and evaluate near isogenic lines with phenotypic variants for fiber and leaf trichomes. Objective 3 - Conduct a regional and national cotton variety testing program to generate supporting data that can be applied in a diverse set of situations to develop genetic and/or production strategies to improve the cotton crop. Sub-objective 3A - Test annually new germplasm and varieties for yield, fiber and seed quality and maintain a database of the evaluation. Sub-objective 3B - Compare and validate effects of changing the source or method of fiber quality analyses or seed assays.
1b. Approach (from AD-416):
Use a coordinated approach to develop new germplasm and tools to improve cotton fiber and seed, as well as maintaining a regional and national cotton testing program relevant to the needs of the cotton community. Use cotton variants as a tool, as well as novel cotton lines developed from intermating diverse germplasm, to reduce the existing negative association between yield and fiber quality. Improve the efficiency and accuracy of the intermating and introgression techniques by using DNA markers to track the intermating and introgression processes over generations. Use the rapidly expanding arsenal of molecular techniques to develop and evaluate near isogenic lines with phenotypic variants for fiber and leaf trichomes. Study trichome initiation mechanisms using the isogenic lines. Evaluate the feasibility of using cotton genotypes with low attachment strengths to improve ginning efficiency and decrease fiber damage during the ginning process. Increase the use of cotton seed for animal and fish feed by introgressing traits that make the seed less toxic. Improve cotton’s host plant resistance (HPR) to pests, by introgressing into adapted lines, existing traits that improve the levels of protective compounds in the plant and the nectariless trait that decreases the plant’s attractiveness to insects. Provide a venue to test elite lines and new varieties through coordinated multi-location tests, and use the data generated to compile a database of performance data across locations and years. Evaluate the potential of new fiber quality measurements compared to existing measurement methods.
3. Progress Report:
Broaden cotton genetic base through introgression of exotic cotton relatives. Growers would like higher yields and better quality fiber, however, there is a negative correlation between fiber quality and yield. During 2014, ARS scientists used special crossing techniques to inter-mate diverse exotic cotton lines in order to break this negative association in addition to broaden the Upland cotton genetic base. New methods using DNA markers are being used to track the intermating process and ensure that the intermating is working efficiently. Field evaluation of elite cotton lines introgressed with less toxic terpenoid aldehyde (TA) compounds. The cotton plant and seed contain several TA compounds (gossypol, hemigossypolone and heliciocides) which protect the cotton plant from pests and disease, but also inhibit the growth of monogastric animals and humans that eat the cotton seed. There are wild cottons that contain modified less toxic compounds and the trait responsible for this was previously transferred into elite cotton lines. In 2014, the ARS scientist completed the first year of a three year evaluation of the improved cotton lines. The evaluation includes yield and fiber tests as well as high performance liquid chromatography analyses of TA levels. These lines could be used to develop cultivars where the seed as well as the fiber can provide better income for growers. Developing elite cotton lines with improved terpenoid aldehyde (TA) profile, high yield and good fiber traits. Previously, fifty exotic cotton lines were evaluated for the TA compounds gossypol, hemigossypolone and heliciocides. In 2013, ARS scientist selected six lines, with the best combination of low TA levels in the seed and higher TA levels in the other plant tissues. The six lines were crossed with four elite lines and one cultivar at the cotton winter nursery in Mexico. In 2014, progeny from the crosses were self-pollinated to produce F2 generation. The goal is to develop elite lines with an improved TA profile while maintaining yield and good fiber traits. National Cotton Variety Test (NCVT), a multi-location test for breeders to evaluate new cotton material and provides a database of performance data across locations and years. The 2014 NCVTs were conducted at 30 locations with a total of 51 entries being tested at multiple locations. This includes a Regional High Quality Test at 8 locations to identify new lines with better quality fiber. In addition, spinning experiments were conducted by ARS scientists in Stoneville, MS, using a test where small samples were spun into yarn and evaluated to determine how well the fiber processed into textile goods. Improvements were made to the spinning trials to allow for two replicates of each sample, unlike previous years where all processing was done with no replication.
1. Identifying the optimal number and location for testing new cotton elite lines. When testing new cotton elite lines to decide which to advance as cultivars, it is critical that the lines be evaluated under enough different growing environments to adequately assess the elite lines, but keep the number to a minimum to reduce development costs. ARS researchers at Stoneville, Mississippi, leveraged the information collected from the National Cotton Variety Test (NCVT), to evaluate data from elite lines tested at 10 locations between 2003 and 2009. The locations covered the cotton belt from South Carolina to New Mexico, and the data was used to determine number of locations and/or years needed to evaluate the lines and to determine if some locations were better for detecting differences in the elite lines. The results indicated that more locations was not a substitute for multi-year testing and it was advisable to test for two years at multiple locations that included at least two locations in the regions from South Carolina to Louisiana and tests in Western region as these locations were significantly different from the other regions. These results will help breeders decide the most effective number of years to test as well as how to select locations to obtain the best data for the cost.
2. Saving energy and reducing ginning costs by improving ginning efficiency. To remain competitive, the American cotton grower needs to save on production and processing costs wherever he/she can. Cotton cultivars differ in how strongly fibers are attached to the seed, and cultivars with reduced fiber-seed attachment force have the potential to be ginned faster with less energy and fiber damage. ARS researchers at Stoneville, Mississippi, conducted a series of studies that confirmed there was heritable diversity among current cultivars for ginning efficiency, showed the trait was heritable and that genetic advances from selection were possible. They also showed that other traits such as percent fuzz were correlated with ginning efficiency and could also be used as selection targets. These results will help breeders develop cotton cultivars that gin faster with lower ginning energy requirements. Because less force is required to remove the fiber from the seed, there is less damage and the fiber also maintains better quality when delivered to the textile mill.
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