Location: Crop Germplasm Research2009 Annual Report
1a. Objectives (from AD-416)
Objective 1: Conserve and distribute a wide diversity of cotton genetic resources and associated information to researchers and breeders worldwide. Sub-objective 1.A: Strategically expand U.S. holdings of cotton genetic resources, especially wild relatives of cotton, through germplasm exchanges and plant explorations. Sub-objective 1.B: Maintain more than 10,000 cotton accessions in the active collection. Regenerate cotton accessions at the Cotton Winter Nursery (CWN) each year, with priorities determined by user input and by seed inventory and viability. Increase the proportion of the active collection backed-up at the National Center for Genetic Resources Preservation (NCGRP). Sub-objective 1.C: Distribute on request cotton accessions and information that meet the specific needs of researchers and breeders. Sub-objective 1.D: Collect and submit data to GRIN and CottonDB. Objective 2: Strategically evaluate (phenotype) cotton genetic resources for priority biotic and abiotic stress resistance, quality factors, and other priority agronomic traits. Sub-objective 2.A: Evaluate cotton accessions in the Cotton Winter Nursery for fiber properties (strength, length, micronaire, elongation). Sub-objective 2.B: Coordinate the cooperative evaluation of cotton genetic resources for other priority agronomic traits, such as resistance to various abiotic and biotic stresses. Sub-objective 2.C: Incorporate the evaluation data collected above into GRIN, CottonDB, and other genetic resource databases. Objective 3: Characterize the genetic variability in cotton genetic resources via genotyping with leading edge genetic marker technology. Sub-objective 3.A: Genotype priority cotton accessions with SSR genetic markers, and incorporate genotypic data into GRIN, CottonDB, and/or other databases. Sub-objective 3.B: With the genotypic information obtained above, measure genetic variation within and among cotton accessions. Sub-objective 3.C: Coordinate the cooperative DNA marker characterization of the cotton germplasm collection with a core subset of portable molecular markers developed by the sister project (6202-21000-030-00D).
1b. Approach (from AD-416)
To conserve and distribute a wide diversity of cotton genetic resources (Objective 1), 400-500 new accessions will be added to the collection – primarily through germplasm exchanges with national collections held in China, France, India, Russia, and Uzbekistan. Plant explorations will also be conducted as funds for this purpose are provided by the Plant Exchange Office section of the National Germplasm Resources Laboratory. Approximately 1,000 accessions (10% of the collection) will be regenerated each year, with priority for regeneration based upon age of seed and germination rate. We will distribute upwards of 4,000 accessions per year for a total worldwide distribution of approximately 20,000 accessions over the period of this project plan. To meet the goal of evaluating cotton genetic resources for priority biotic and abiotic stress resistance, quality factors, and other priority agronomic traits (Objective 2), basic descriptor data will be collected during the grow-outs for regeneration in the Cotton Winter Nursery or in our greenhouses and specific collaborations will be established to evaluate germplasm for responses to biotic and abiotic stresses. To facilitate incorporation of evaluation data into GRIN, CottonDB, and other genetic resource databases, methods of electronic data collection and downloading into appropriate databases will be developed and cooperative efforts with managers at the Database Management Unit will be established to create new and appropriate fields within the GRIN database. More detailed or complex data will be stored in the local database until GRIN establishes the proper formats for public display. Efforts to characterize the genetic variability of the collection via genotyping with genetic marker technology (Objective 3) are being pursued in cooperation with the sister project (6202-21000-030-00D), and are focused on developing a comprehensive set of 208 core DNA markers for evaluation. To evaluate the suitability of the markers, a standard panel of the U.S. Cotton Germplasm Collection is being used. When appropriate markers have been identified, the DNA marker profile of a preselected set of 384 accessions representing a subset of the U.S. Cotton Germplasm Collection will be scored. Genetic diversity and phylogenetic relationships will be evaluated using population genetic software such as NT-SYS and Arlequin. The 384 samples will be clustered using the computer package PAUP and/or the neighboring-joining method. Once a core set of DNA markers is established and validated on the selected subset of the U.S. Cotton Germplasm Collection, the markers will be made available to cooperators, and coordination will be provided to accomplish the work in an efficient manner to prevent duplication of effort. Standard use of the core DNA markers will enable all characterizations and evaluations of Gossypium germplasm to be pooled into a common, publicly available database for analysis and interpretation across different gene pools or germplasm sources.
3. Progress Report
Work under this project during FY 2009 resulted in significant progress in characterization, seed increase, seed distribution, and data input into databases for accessions of the germplasm collection. Seed of almost 1100 accessions of the National Cotton Germplasm Collection were increased, descriptor information was collected on the same number for characterization or identity confirmation, and more than 1800 accessions were distributed in response to requests from 102 individuals or institutions. Bar coding was successfully implemented in nearly all phases of the operation in conjuction with mobile Personal Digital Assistants, increasing capacity for data gathering, uploading into local and Germplasm Resources Information Network (GRIN) databases, and in management of operations. About 40 accessions were added to the collection, either from prior collecting expeditions (20), germplasm exchanges (9), or from elite germplasm whose Plant Varitey Protections (PVPs) have expired (15). A comparative investigation of the fiber properties obtained from reference cultivars grown in the Cotton Winter Nursery (CWN) and at numerous locations of the U.S. National Cotton Variety Test revealed that the CWN environment produces fiber values within the range of U.S. environments, indicating that the CWN can be used for fiber evaluation and selection and therefore allowing for increased speed and efficiency in breeding efforts. Another project was initiated to investigate the genetic diversity available in cultivars of the National Cotton Germplasm Collection using molecular biology tools known as molecular markers. In a preliminary project, a subset of 24 Gossypium hirsutum cultivars originating from North Africa, South Africa, China, and the U.S. were screened using 76 Single Sequence Repeat (SSR) markers, and 61 markers were found to be useful in identifying genetic diversity. A replicated evaluation of 62 cultivar accessions from these four nations was initiated at College Station and Lubbock, TX, in collaboration with Texas A&M University, to evaluate genetic diversity using agronomic, molecular, and descriptor data. In collaboration with ARS scientists at Florence, SC, a breeding project was initiated to select for high and low oil percent in cotton seeds using selected Texas race stock accessions from the germplasm collection and selected germplasm lines from an historical South Carolina cotton collection as parents. Also working with ARS scientists in Florence, replicated yield trials of four germplasm pools and 21 F2 populations were planted in College Station and Clemson, SC, to evaluate fiber and agronomic properties, as well as individual plant properties within the four germplasm pools. A final year of evaluation was conducted in an inter-regional, multi-institutional project to identify/develop broadly adapted, high fiber quality cotton germplasm. Data was analyzed, and one line was released to breeders to facilitate ongoing work to develop higher fiber quality cottons for use by U.S. farmers.
1. Development of a High Fiber Quality Cotton Line: Developments in cotton spinning technology and higher international fiber quality standards have placed increasing demands on the U.S. cotton industry for fiber quality improvement. Genetic resources for fiber improvement are available, but many of these have historically been proven to have limited regional adaptation. More broadly adapted high fiber quality cotton germplasm resources would greatly facilitate breeding efforts focused on fiber improvement. In a collaborative effort between ARS and academic researchers, several high fiber quality germplasm lines were developed and tested for adaptation and productivity at a number of sites across the U.S. Cotton Belt. The work identified one line (CRB 252) that was broadly adapted and that consistently maintained high fiber quality in different environments. This accomplishment is important because it identifies a specific cotton germplasm resource that will be extensively utilized by breeders in their efforts to develop new, widely adapted and high fiber quality commercial cottons that will enhance the competitiveness of U.S. cottons in the world market.
2. Enhanced Value of the Cotton Winter Nursery in Mexico: Many private and public cotton breeding programs accelerate the pace of germplasm and cultivar development by using tropical nurseries to obtain two generations of cotton reproduction in a single year. The ability to evaluate fiber properties in the Cotton Winter Nursery (CWN), located at Tecoman, Mexico, would further increase the efficiency of cotton improvement efforts. Fiber properties of six cotton cultivars from a standard reference panel, grown over three years in the CWN, were compared to the fiber performance of the same cultivars grown at multiple U.S. locations. The CWN environment gave fiber values well within the range of the fiber values seen in U.S. environments. This is important because it establishes for the first time that fiber quality trials at the CWN will give data fully equivalent to data obtained in U.S. trials. Effective utilization of the CWN for cotton fiber evaluation and selection will significantly accelerate efforts to produce higher fiber quality cottons for planting by U.S. farmers.
Percy, R.G. 2009. The worldwide gene pool of Gossypium barbadense L. and its improvement. In Paterson, A.H., editor. Genetics and genomics of cotton. Springer, New York, pp. 53-68.