Location: Crop Germplasm Research2012 Annual Report
1a. Objectives (from AD-416):
The objectives of this project are to characterize, evaluate, and enhance cotton germplasm, and augment, improve, and maintain germplasm databases. Evaluation and enhancement efforts will focus on agronomic, fiber quality, and biotic and abiotic stress tolerance traits important to the cotton industry and to the improvement of cotton as a crop. Specifically, this project will investigate the genetic diversity and agronomic potential of improved global cultivars in order to: 1) determine the genetic diversity and relationships among cultivars from cotton-growing regions of the world, including Africa, Brazil, China, Greece, India, Pakistan, Russia, Turkey, the U.S., and Uzbekistan; 2) identify within these global cultivars agronomic traits with potential for enhancing the breeding programs for cotton grown in Texas; and 3) more fully characterize a portion of the U.S. Cotton Germplasm Collection. Efforts to characterize and evaluate germplasm will be complemented and augmented by molecular mapping efforts on the cotton genome and database improvement and maintenance efforts.
1b. Approach (from AD-416):
Cotton germplasm will be characterized and evaluated for agronomic traits, fiber quality, and biotic and abiotic stress tolerance. Molecular marker profiles will be used to establish genetic relationships between germplasm lines and to characterize genetic diversity within germplasm sets. Molecular mapping techniques will be employed in characterizing genome structure. Data collected from phenotypic characterizations and evaluations, and from molecular characterization and mapping will be maintained in the CottonDB and GRIN databases. An initial project, occurring during the first three years of the project, will involve the phenotypic evaluation and molecular characterization of global cultivars and elite germplasm. Phenotypic evaluations will focus on agronomic, yield, and fiber quality traits of cultivars. Morphological descriptor data will also be taken. Phenotypic evaluations will occur in replicated tests on cooperator facilities at College Station, TX, using seed provided by the ARS. Phenotypic evaluation will be a joint effort. Molecular characterization of the cultivars/elite lines will take place in ARS facilities by ARS personnel. Molecular diversity will be assessed using a set of 208 simple sequence repeat (SSR) markers. Data from the molecular diversity assessment will be used to calculate genetic similarity coefficients. This coefficient will be further used in a cluster analysis to construct a dendrogram showing relationships between cultivars and a principal component analysis to observe how individual cultivars form groups based on SSR similarities. An analysis of molecular variance (AMOVA) based on the SSR data will measure genetic structure between and among the twelve groups of cotton cultivars. The project may be extended to other germplasm and beyond the initial three years. Complementary efforts to supplement characterization of germplasm through physical mapping of the cotton genome and database development will occur.
3. Progress Report:
The goal of this project is to characterize and evaluate the genetic variation in the National Cotton Germplasm Collection. In FY 2012, work to evaluate genetic diversity for fiber quality traits in germplasm collection cultivars from North Africa, South Africa, China, and the U.S. was completed. Cultivars from the collection were test crossed to high and low fiber quality lines and were intercrossed with each other in all combinations to determine their general combining ability for fiber length. General combining ability is a measure of how well two parents combine to produce superior offspring. Results indicated that cultivars from Africa and obsolete U.S. cultivars could harbor genetic variation for improving fiber length that is not currently being exploited in cultivar development. Analyses of the genetic diversity of cultivars from North Africa, South Africa, China, and the U.S. as measured by genetic tools known as molecular markers was completed and reported in FY 2012. The work established that greater genetic variation occurred among cultivars of the same national origin than between cultivars of differing national origin. Based upon these results, it would appear that country of origin is an inadequate criterion for selecting cultivars with diverse molecular genetic backgrounds. Work by this project has developed, and will continue to develop, essential information on the genetic diversity of the National Cotton Germplasm Collection, and will identify useful genetic traits for exploitation by breeders to develop improved cotton cultivars for U.S. farmers.