Submitted to: Plant Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 27, 1998
Publication Date: N/A
Stand establishment is a complex field trait comprising seed germination, seedling emergence, and seedling survival. Poor stand establishment is associated with empty field spaces, 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. Rapid emergence and tillering also allow earlier flooding of rice fields which saves water and suppresses weeds. The semidwarf gene, sd1, that is used in rice throughout the world has been found to be closely linked to reduced seedling vigor and mesocotyl 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 developed from two tropically-adapted sd1varieties 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 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. Component analysis greatly enhances the identification of QTLs associated with complex traits.