Introgression of agronomic traits associated with molecular markers from Oryza nivara Sharma and Shastry and O. glaberrima Steud. into O. sativa L

Wild species of rice have been regarded as a potential source of genetic diversity to improve cultivated rice. The purpose of this study was to identify quantitative trait loci (QTL) associated with agronomic traits using simple sequence length polymorphisms (SSLP). A BC₂F₂ population of 192 families was developed from a cross between the high yielding japonica cultivar M-202 and the wild species Oryza nivara (accession 100195). Ninety-one SSLP markers distributed through the twelve rice chromosomes were used to identify by single point analysis QTL controlling 15 characteristics of agronomic importance: Grain yield (GY), grain weight (GW), number of spikelets per panicle (NSP), panicle length (PL), number of panicle per plant (NP), fertility of spikelets (FS), kernel length (KL), kernel width (KW), kernel length/width ratio (KLW), plant height (PH), and days to flowering (DTF), and the seedling vigor related traits shoot length (SL), coleoptile length (CL), mesocotyl length (ML) and root length (RL). A loglikelihood (LOD) threshold of 2.0 was used. SL, CL, ML and RL were measured in slantboard tests conducted at 20 C. Sixteen QTL were identified controlling GY and yield related traits GW, NSP, PL, and NP, with single marker effects ranging from 4.9% (GW) to 23.6% (NP). Fourteen QTL affected kernel dimension traits with single marker effects varying from 5.1% for KLW to 21.3% for KL. Seven QTL controlled SL, two controlled CL, four each controlled ML and RL. Two and five QTL were found affecting PH and DTF, respectively. 58% of the positive alleles were contributed by the wild parent, including those for SL, the most important determinant of seedling vigor in water-seeded rice, with effects of single markers ranging from 5.3% to 14.5% of phenotypic variation. The contribution of O. nivara with positive alleles for most of the agronomic traits suggests that it is a promising source to improve temperate japonica cultivars. Further studies must be carried out to verify the potential of the identified QTL in other related genetic backgrounds, such as tropical japonica and upland rice cultivars.