Fine mapping and grain yield analysis of a major QTL controlling primary branch number in rice (Oryza sativa L.)

Panicle size is one of the most important agronomic traits highly associated with grain yield in rice. For quantitative trait locus (QTL) analysis and breeding utilization of panicle size in rice, a large panicle rice line YR1 was used as a donor to cross and backcross with a commercial cultivar Ningjing 1 (NJ1), and developed backcross populations. In a BC2F2 population, a total of 3 QTL associated with panicle size were found on chromosome 1 and 8. Two of the QTLs, qPBN1 and qGNP1, were mapped to an interval on chromosome 1, where a previously cloned gene GN1a was located. qPBN8, a major QTL for primary branch number on chromosome 8, was finally narrowed to a 51.8 kb region, containing reported gene OsSPL14 regulating branch number and plant architecture. Through sequence and expression comparison, the qPBN8 was considered to be the allele of OsSPL14. The investigation of yield structure in six pairs of near-isogenic lines revealed that the effects of qPBN8 on grain yield were related to the length of vegetative period. The qPBN8 allele of large panicle was suitable for late-maturing varieties to improve yield.