Genetic analysis and gene-mapping of two reduced-culm-number mutants in rice

In the present study, in order to systematically dissect the genetic mechanism of rice (Oryza sativa L.) tilling for the super rice ideotype and the model system of branching development, two ethyl methane sulfonate-Induced rice reduced culm-number (rcn) mutants from the progeny of Nippobare (O. sativa ssp. japonica), namely rcn8 and rcn9, were used. Their maximum tillers were both less than 4. In addition, rcn9 had another major feature of rust-spotted leaves. Allelic tests between these two mutants and seven other recessive few-tiller mutants revealed that they were previously unknown loci. Genetic analysis showed that the rcn traits were all controlled by a pair of different recessive genes, designated as RCN8 and RCN9, respectively. Two F-2 populations derived from crosses between the rcn8 or rcn9 mutants and 93-11 were constructed. Linkage analysis using two rcn F2 mapping populations with published simple sequence repeat markers demonstrated that the RCN8 and RCN9 genes were mapped on the long arm of chromosome 1 (119.6 cM) and the short arm of chromosome 6 (63.6 cM), respectively. The results of the present study are beneficial to map-based cloning and functional analysis of the RCN8 and RCN9 genes.