2012 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.
Three Pima varieties were identified for earliness, lint yield, and superior fiber quality at Stoneville, MS. These Pima varieties will be crossed with five Delta cultivars to transfer their superior fiber quality. To broaden the genetic base of Delta cotton, eleven crosses involving Gossypium (G). hirsutum mutants, Acala varieties, and FiberMax cultivars crossed and backcrossed with four best-adapted Delta cultivars were screened to identify useful germplasm for the region. To break the negative linkages between lint yield and fiber strength, two sets of polycrosses, each involving eight diverse cotton germplasms, were made. Crosses were also made between MD 15 (superior quality) and SG 747 (good yielder) to develop recombinant inbred lines to use in quantitative trait loci (QTL) analyses for marker assisted selection. Backcrosses and random crosses are also being attempted with this cross to break the linkage. An improved mutant population (MD 15 M4) with enhanced fiber quality has been proposed for release. On an individual plant basis, eight individual mutant plants with fiber length of 3.25 to 3.43 centimeters (1.28 to 1.35 inches) and six mutant individual plants with fiber strength of 49.1 to 52.3 grams/tex have been selected for further screening. Cotton varieties with partially naked seed traits gin faster and have lower short fiber content and neps. A new gene conditioning naked-tufted seed coat with high lint turnout in a mutant germplasm SC 9023NS-57-13-2-1 has been identified. In other tests, 153 segregating materials ranging from F2 to F5 generations were selected for further testing for lint yield, fiber quality and the nectariless trait. In a collaborative project called ‘Genomics and breeding of cotton with high ginning efficiency between three ARS research units, two populations were created with traits for ginning rate and ginning energy. Experiments were designed to evaluate F2 and F3 populations derived from multiple crosses between nine germplasm lines and five cultivars for genetic values of lint yield and fiber properties and genetic correlations among fiber traits. Individual plant selections were initiated in F3 progenies for lint yield and fiber quality, and F4 progeny lines are under evaluation in the current season. F2 populations derived crosses between five nectariless lines in a half diallel design are being evaluated for lint yield and fiber properties. An experiment was started to analyze effects of late planting on lint yield, fiber quality and breeding values.
Identification of a new fuzzless seed locus in an upland cotton mutant. Normal cottonseed is covered with lint and fuzz; lint is a textile fiber whereas fuzz is a short fiber that is difficult to gin from the seeds, resulting in increased energy use, short fiber content and neps (entangled fibers). Two widely studied mutants have fuzzless seeds and also have very low lint percent (ratio of cotton lint to cottonseed that together make up the seed cotton that is picked) which has discouraged use of these mutants in breeding programs. In 1997, a mutant plant having fuzzless seed with tufts attached to one end of the seed was identified from commercial variety SC 9023 treated with ethyl methanesulfonate. An ARS scientist at Stoneville, MS, showed that this trait is controlled by one recessive gene and has lint percent as high as most commercial cultivars (38 to 40%), gins faster, and has low short fiber content and neps. Breeders can use this mutant in cotton breeding programs to improve fiber quality without having to remove the adverse effect of low lint percent.
Genotype × environment interactions and performance stability of cotton cultivars across major regions in U.S. Cotton Belt. Determination of genotype by environment interactions can help identify cotton cultivars with stable performance across different environments. Data from the National Cotton Variety Trial (NCVT) were used to determine the influence of cotton genotype and environmental interactions on breeding success and to identify germplasm with wide adaptation to environments across U.S. Cotton Belt. Results indicated that environments in U.S. Cotton Belt are highly unpredictable for lint yield. It is recommended that superior genotypes with wide adaptation to environments across locations and years be selected by breeders for improvement of lint yield and fiber quality. Cultivar ‘DPL 445BR’ had high yield and good stability across most of the environments where it was tested and can be a good standard in national variety tests.
Analysis of additive and dominant genetic components facilitate introgression of novel genes into Upland cotton cultivars. Determination of additive and dominant correlations among fiber traits can help breeder simultaneously improve multiple fiber traits. It was determined in germplasm lines Species Polycross (SP) 156 and SP2015 that lint yield and yield components (boll number, lint percent and seed index) were mainly controlled by genetic effects with additive and dominant variance components larger than 66% of total phenotypic variance. The germplasm lines had both positive additive effects and positive predicted dominant effects for lint yield and yield components, and genetic analysis indicated that yield components should be balanced in pure line development. These results should promote utilization of Species Polycross germplasm populations in cotton breeding and the balancing of yield components during selection efforts to genetically improve lint yield.