Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Other
Publication Acceptance Date: February 11, 2000
Publication Date: N/A
Technical Abstract: Stand establishment is a complex field trait comprising seed germination, seedling emergence, and seedling survival. Increased vigor and cold tolerance can improve stand establishments, allow earlier planting to avoid seasonal rains and lengthen the growing season, and allow deeper planting to take advantage of soil moisture. Unfortunately, the sd1 gene used throughout the world to produce semidwarf rice varieties has been found to be closely linked to poor seedling vigor due to shortened mesocotyls and coleoptile. This study identified QTLs associated with components of seedling vigor in a population of recombinant inbred lines (RILs) derived from a cross of Lemont and Teqing. The region of chromosome 1 reported to contain sd1 was found to contain QTLs for mesocotyl and coleoptile lengths. Complementary gene action between the mesocotyl QTL and a QTL on chromosome 7 resulted in progeny with mesocotyl up to four times longer than those of either parent. Teqing and several RILs which were identified containing th desired seedling vigor allele on chromosome 1 and sd1 could serve as important breeding parents to increase the mesocotyl length and seedling vigor of U.S. semidwarf rices. Component analysis, whereby one focuses on highly heritable components of a complex and environmentally sensitive trait, can greatly enhance QTL mapping efforts. Analysis of field emergence data located five QTLs, some of which were significant in only one of the three years. Conversely, analyses of component traits (e.g., elongation of mesocotyl, coleoptile, shoots and roots and ability to emerge through deep soils) identified these five loci plus 15 additional QTLs putatively associated with seedling vigor. These may be important in the development of improved sd1 cultivars for use in direct-seeded culture.