Submitted to: Proceedings International Rice Genetic Symposium
Publication Type: Proceedings
Publication Acceptance Date: October 22, 2001
Publication Date: N/A
Poor stand establishment is associated with empty spaces in the field, stressed seedlings, and asynchronous plants, all of which reduce crop yields and quality. Increased seedling vigor and cold tolerance can improve stand establishment and allow rice to be planted earlier, avoiding seasonal rains and lengthening the growing season to allow economical ratoon cropping. Unfortunately, use of the sd1 gene to produce semidwarf rice varieties has often been associated with reduced seedling vigor due to shortened mesocotyl and coleoptile lengths. This study identified QTLs associated with components of seedling vigor relevant to direct-seeded sd1 rice produced in the semi-tropical conditions of southern USA. A population of 259 RILs derived from a cross between two tropically-adapted sd1 varieties, Lemont and Teqing, was evaluated for seedling vigor and emergence under field and laboratory conditions. Interval analysis using 175 RFLP loci identified five QTLs for field-plot emergence, two for germination, four for emergence through deep soil, four for shoot elongation, four for root elongation, two for mesocotyl elongation, and eight for coleoptile elongation. Complementary gene action between the two mesocotyl QTLs resulted in progeny with mesocotyl lengths and emergence field trait compromising germination, emergence, and seedling survival. Field-emergence data accounted for each of these aspects of seedling vigor, but revealed only five putative QTLs for seedling vigor. Conversely, the analysis of component traits identified these five loci plus 15 additional vigor QTLs. Component analysis greatly enhances the identification of QTLs associated with complex traits such as seedling vigor.