Title: Genetic diversity for cold tolerance at germination in the US rice collection Authors
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 22, 2010
Publication Date: February 22, 2010
Citation: Mcclung, A.M., Gibbons, J., Duke, S.E., Yan, Z., Nelms, A.M., Yan, W. 2010. Genetic diversity for cold tolerance at germination in the US rice collection. Rice Technical Working Group Meeting Proceedings. CDROM P.47. Technical Abstract: Rice production practices are constantly being modified as a result of the availability of new technologies and the changing economic picture. Farmers are planting rice at least one month earlier than a decade ago. With increasing interest in alternative cropping systems, minimum tillage, and water conservation, there is a need to develop rice cultivars that have improved seed germination and vigor under the cold temperatures that can exist during early spring plantings. Such cultivars will have improved stand establishment and will better compete with weeds at a time when herbicides are not as effective. In addition, cultivars that have improved vigor under cold temperatures will allow harvest earlier in the season, thus reducing irrigation demands during late summer. The objectives of this study were to survey rice germplasm to identify accessions with improved seedling vigor under cold temperatures and, ultimately, to identify genetic markers linked to this trait that can be used by breeders for varietal improvement. We screened some 2600 rice accessions including 1685 diverse cultivars in the USDA “Core” collection, 823 accessions from “Temperate” regions, 69 UAR “Breeding” lines, and 41 “Genetic Stocks” and mapping parents. Seed for accessions in each of these categories were produced in the same environment. Some 400 accessions were common to the Core (produced in 2007 and stored at 4C) and Temperate (produced in 1999 and stored at 4C) groups allowing us to evaluate the impact of seed source (production year and storage) on vigor. Each accession was evaluated for germination in growth chambers using thirty seed and three replicates at 12C and two replicates at 26C. Each seedlot was cleaned, sterilized with 10% Clorox, and seed were placed on paper towels that were uniformly moistened then sealed prior to being placed into the growth chamber. Percent germination was determined approximately 7 days after initiation for the warm treatment and following 30 days of the cold treatment. The accessions were compared to repeated checks Quilla 66304 (PI 560281) (70% germination at 12C), Lemont (48%), and Zhe 733 (40%). Initial results demonstrated that cold temperature germination for the accessions ranged from 0 to 100%. Results identified 590 cultivars (23% of the accessions) that were equal to or better than Quilla 66304 for cold germination. Accession 89-5 (PI 614993) originating from Sichuan, China had plant and grain quality traits comparable to southern US long grains along with 79% germination under cold temperatures. Significant difference was observed due to seed source (1999 vs 2007) for both warm and cold germination treatments but there were no consistent trends indicating that seed source can be a confounding factor. Within the Core and Temperate groups, 31 cultivars were identified that had >90% germination at 12C. These originated from countries in both tropical and temperate climates. On-going analysis will include an association mapping study using 70 SSR markers that have been determined on accessions in the Core group and a correlation analysis of plant phenotype with cold germination and vigor.