Molecular marker-aided characterization of seedling vigor in rice for direct-seeded culture

摘要

Direct-seeding is increasingly being practiced by Filipino rice farmers but all modern varieties released so far have been bred for and selected under transplanted rice culture. Seedling vigor (SV) is important for optimum field establishment and increased weedcompetitiveness under direct-seeded conditions. We analyzed the genetic variation for SV traits in 49 promising parents for breeding direct-seeded rice using conventional and molecular assays. Substantial quantitative variation was observed for shoot, root, mesocotyl and coleoptile lengths in slantboard tests. High-SV genotypes were identified in addition to known SV genetic donors-Itahca Livorno (IL) and Black Gora (BG). Molecular markers, identified earlier in both indica and japonica rice to flank quantitative trait loci (QTL) underlying SV traits, were used to characterize genetic diversity in the test materials. Cluster analysis using 39 RAPD loci flanking 11 SV QTL revealed genotypic differences at SV QTL regions and discriminated the test varieties into eight major clusters. High-SV genotypes that grouped differently from IL and BG may possess alternative SV QTL alleles. This was supported by the different grouping pattern that resulted when 68 randomly selected RAPD markers were used in cluster analysis. Crossing high-SV genotypes from different clusters may led to new populations segregating for the maximum number of high-SV alleles, thereby facilitating the development of superior varieties for direct-seeded rice culture.