Genetic and physical mapping of -, a pleiotropic QTL for heading date and yield-related traits in rice

A QTL, -, has been resolved into a single Mendelian locus controlling heading date and yield-related traits in rice. The trait-performance of the three genotypes for the QTL in the BC5F2 or BC4F2 populations (with cultivar Teqing or YuetaiB as recurrent parents) indicated that the Lemont (donor parent) allele at - locus showed a positive and pleiotropic additive effect on heading date (HD), plant height (PH), panicle length (PL), and spikelets per panicle (SPP).The QTL’s additive effects varied for different traits according to its heritabilities, it showed a largest effect on HD with a heritability of 98%, secondly on PL with a heritability of 70–87%, then on PH with a heritability of 56–61%, and lastly on SPP with a heritability of 45–47%. In addition, the QTL showed a weaker dominant effect, significant only on HD and PL. With an advanced BC5F2 population, - was firstly mapped to a 299 kb genomic region by recessive-class analysis. Then, with a set of segment substitution lines, substitution mapping located - within a chromosomal region between markers ID3468 and ID4891, corresponding to 31.4 kb on the genome sequence of Nipponbare. Sequence analysis of an ORF Os08g07740 which encodes a histone-like CCAAT-box binding transcription factor suggested that the ORF would be tentatively referred to as the first strong candidate gene. All these results demonstrated that - is a pleiotropic QTL for heading date and multiple yield-related traits and would be of great value to the improvement of rice productivity.