Genetic dissection of seedling and early vigor in a recombinant inbred line population of rice

Rice (Oryza sativa L.) cultivars of strong seedling and early vigor is one of the most important factors associated with the increase of yield potential. With 285 recombinant inbred lines derived from a rice cross between a tropical japonica var. Lemont and an indica var. Teqing with a higher level of vigor than Lemont, seedling/early vigor related traits (plant height, dry weight and seed weight) during 14-44 days post sowing were assessed at an interval of 10 days. Time-related QTL mapping identified 18 QTL or chromosomal regions for the three traits by using a linkage map consisting of 222 marker loci. Of the regions, four produced significant effects on the traits at three measuring stages while the others showed effects only at one or two stages. Comparison of the effect magnitudes indicated that the region qSEV-5-2 on chromosome 5 showed a major effect on seedling/early vigor during stages 1-3 but by stage 4, the major role was substituted by the region qSEV-3-4 on chromosome 3. Five regions simultaneously showed effects on two or three vigor related traits. For each of the five regions, comparison of its LOD peak locations and LOD curve shapes detected for different traits to some extent suggested that within each of the three regions (qSEV-3-1, qSEV-3-4 and qSEV-5-2), there could be a single locus showing a pleiotropical effect on both plant height and dry weight while within each of the three regions (qSEV-2-2, qSEV-4-2 and qSEV-5-2), there could be at least two linked loci, one showing effect on seed weight and the other on plant height. The chromosomal regions or QTL identified in the current study were compared with those previously reported for the other traits. (c) 2006 Elsevier Ireland Ltd. All rights reserved.