Validation of QTLs associated with spikelets per panicle and grain weight in rice

Abstract

In this study, a near-isogenic line (BC4F10) CR572 developed by introgressing a chromosomal segment fromOryza rufipogon(accession no. 105491) into theOryza sativasubsp.japonicacv. Hwaseong was found to exhibit a significant increase in the number of spikelets per panicle (SPP) and grain weight compared with the recurrent parent Hwaseong. Quantitative trait locus (QTL) analysis in F2generation derived from the cross between CR572 and Hwaseong revealed that two QTLs,qSPP1andqTGW1, were linked to a simple sequence repeat marker, RM283, on chromosome 1. The additive effect of theO. rufipogonallele atqSPP1was 13 SPP, and 21.6% of the phenotypic variance was explained by the segregation of RM283. TheqTGW1QTL explained 19.1% of the phenotypic variance for grain weight. Substitution mapping was carried out with five F3lines derived from F2plants having informative recombination breakpoints within the target region. Substitution mapping indicated the linkage ofqSPP1andqTGW1. The grain yield of CR572 was 18.2 and 15.8% higher than that of Hwaseong at two locations, respectively, mainly due to the increase in 1000-grain weight and SPP. These results are very useful for QTL cluster transfer by molecular marker-assisted selection in rice breeding programmes and for QTL gene cloning by map-based cloning.