Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 9, 2000
Publication Date: N/A
Technical Abstract: Stand establishment is a complex field trait comprising seed germination, seedling emergence, and seedling survival in spite of pressures from pests and weather. Poor stand establishment is associated with empty spaces in the field, stressed seedlings, and asynchronous plants, all of which reduce crop yields and quality. The semidwarf gene, sd1, that is used in rice throughout the world has been found to be closely linked to poor seedling vigor and reduced mesocotyl length. This study identified QTLs associated with components of seedling vigor relevant to direct-seeded sd1 rice produced in the semi-tropical conditions of the southern USA. A population of 259 RILs developed from two tropically-adapted sd1 varieties (Lemont, a US tropical japonica, and Teqing, a Chinese indica) was evaluated for seedling vigor and emergence under field and laboratory conditions. Interval analysis using 175 RFLP loci identified three 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 (one of which is closely linked to sd1) resulted in progeny with mesocotyl lengths and emergence capabilities greater than either parent. Each year of field emergence data identified a single QTL that was not associated with emergence in the two other years. The analysis of component traits, however, identified these three QTLs plus several additional loci putatively associated with seedling vigor. Component analysis greatly enhances the identification of QTLs associated with complex traits such as seedling vigor.