Plant & Animal Genome VI Conference

P76

QTL-BASED CLASSIFICATION OF RICE CULTIVARS FOR DIRECT-SEEDING

Plant Breeding and Biotechnology Division, Philippine Rice Research Institute (PhilRice), Maligaya, Muñoz, Nueva Ecija 3119, Philippines

Quantitative trait loci (QTL) for seedling vigor (SV), a trait that promotes optimum stand establishment and increases the rice plant's weed competitiveness under direct-seeded culture, have been mapped to different rice chromosomes in both indica and japonica rice. Molecular markers flanking these QTL could be useful as diagnostic probes for introgressing and/or pyramiding favorable SV alleles. We assayed 49 promising parents for breeding direct-seeded cultivars at 37 RAPD loci flanking 11 SV QTL and compared their respective genotypes with: (a) that of Italica Livorno (IL), a cultivar used to map SV QTL in japonica rice, (b) amongst themselves, and (c) actual SV performance based on slantboard tests. Cluster analysis revealed genotypic differences at regions flanking SV QTL between most test cultivars and IL and discriminated the cultivars into eight major clusters. Phenotypic assays for four SV-related traits-length of shoots, roots, coleoptile and mesocotyl, identified consistently superior genotypes that clustered differently from known high-SV donors (IL and Black Gora), and hence may possess alternative high-SV alleles. The use of inter-cluster crosses to develop new populations that would segregate for the maximum number of high-SV alleles could facilitate the development of superior cultivars for direct-seeded rice culture.