Location: Crop Genetics Research2009 Annual Report
1a. Objectives (from AD-416)
Objective 1 – Develop new and improved combinations of yield and fiber traits and investigate the basic genetic factors related to the improved cottons. Objective 2 – Evaluate populations involving introgressed genes from wild species for agronomic acceptance and determine their genomic relationships. Objective 3: - Identify physiological traits that confer improved yield and fiber quality and investigate new management systems that optimize the performance of diverse varieties through pairing them with alternative production strategies.
1b. Approach (from AD-416)
Assemble germplasms originating from other Gossypium strains, race stocks, species, and genetic-breeding populations. Using genomics and other new biotechnology tools combined with conventional methods, evaluate new germplasms for its potential in developing improved combinations of yield, fiber quality, and pest resistance cottons. Investigate the underlying causes of the negative associations of yield and fiber quality. Determine how the micro-climate and management impact improved yield and fiber quality. Characterize the genetic vegetative-reproductive growth patterns, crop maturity, leaf shape and the physiological variances that interact with crop management. Identify physiological and genetic systems that have potential for being more efficient in developing new cotton cultivar systems that are environmentally safe and results in more competitive USA cottons. Identify biomarkers associated with improved yield and fiber quality for marker assisted selections. In cooperation with other ARS laboratories, describe developmental mechanisms of cellulose synthesis and improved fiber traits. Important fiber traits are fiber length, short fiber content, bundle strength, fineness and maturity.
3. Progress Report
Cooperative research between ARS personnel at Stoneville and Mississippi State University, MS, detected Single Sequence Repeat (SSR) markers that are closely associated with differences in fiber strength (T1) between MD 52ne and its recurrent parent DPL 90ne. After the equivalent of eight backcrosses, MD 52ne consistently averaged 10 to 15% higher bundle strength than DPL 90ne. A population of 186 segregating BC9F2:3 progenies will be evaluated for fiber strength (T1) in field tests at Stoneville, MS. Results of 2008 studies show that the strain MD25 has great potential for germplasm release. In research on cross selecting polycross progenies with array of cultivar types in 4 X 12 crossing design, a total of 39 marker-trait associations were identified and confirmed. In addition, 16 parental lines including 12 elite JC germplasm lines and 4 cultivars were genotyped with 100 SSR markers. The genetic distances among the 16 parents will be used to predict hybrid performance for lint yield and fiber quality. In the agronomic, physiological and crop culture studies, analyses give insight to physiological mechanisms leading to lint yield and fiber quality differences among diverse cotton varieties. Although planting date did not alter the irrigated yields, dryland conditions were much more damaging to the early planted cotton than to the normal planted cotton. Genotype, planting date, and irrigation all impacted multiple fiber traits. In particular, both early planting and dryland conditions increased the short fiber content. Genotypic variation was detected in leaf photosynthesis, leaf chloraphyll concentration, dry matter partitioning, and canopy light interception. These differences will be related to previously reported differences in lint yield, yield components, and fiber quality among the cotton genotypes. In contrast to previous years, the heat stress treatment did not reduce lint yield this year probably because the ambient air temperature was abnormally high during part of the 2008 growing season. Fiber strength was numerically greater when grown under high temperature but not statistically so as had been the case in previous years. Rd (% reflectance) was significantly lower for fiber produced under the heat stress conditions. The number of total Neps was reduced under the high temperature treatment. Starter fertilizer reduced stands counts relative to the plots not receiving any starter fertilizer, probably due to some toxicity from free ammonia near the seeds. Even though stand establishment was reduced, the plots receiving the starter fertilizer produced 4% greater lint yield than the non-starter fertilizer plots, which was statistically significant.
1. Notice of Release of JC Cotton Germplasm Line with Unique Features in Lint Yield and Fiber Quality. High yielding cultivars in Mid South and southeastern regions lack fibers with sufficient strength and length and often have high short fiber content thus failing to meet the needs of the domestic industry and for exports. Four germplasm lines the JC14, JC32, JC60 and JC65 were developed from evaluation and selection of an exotic germplasm population, JohnCotton (JC), derived from crosses among diverse germplasm lines. Lint yield of the four released JC lines ranged from 830 to 1190 kg/ha, compared to 1565 kg/ha of the high yielding cultivar DP555BR and 1090 kg/ha of high fiber quality cultivar PHY72. JC32 and JC65 produced lint percentage significantly greater than that of PHY72, and all four released lines displayed fiber quality superior to the high quality check PHY72. The release of these germplasm lines provides cotton breeders with opportunities to improve fiber quality while maintaining productivity in commercial cultivars.