Bin mapping-based QTL analyses using three genetic populations derived from indica-japonica crosses uncover multiple grain shape heterosis-related loci in rice.

Exploitation of heterosis between indica and japonica has important significance in scientific research and agriculture application. However, the molecular mechanism of grain shape heterosis in indica-japonica hybrid remains unknown in rice (Oryza sativa L.). To reveal the genetic mechanism of grain shape in indica--japonica hybrid, we constructed a high-generation recombinant inbred line (RIL) population and two testcross hybrid populations derived from the cross of RILs and two cytoplasmic male sterile material (YTA and Z7A) and then performed a bin mapping-based quantitative trait locus (QTL) mapping of multiple grain shape traits, such as grain length (GL), grain width (GW), and grain length-to-width ratio (GLWR). A total of sixteen QTLs and 30 heterosis-related QTLs of grain shape traits were detected. We found that GS3, GS5, and OsPPKL2 were also correlated with grain shape both in RILs and two testcross hybrid populations. Homologous gene analysis emphasized two candidate grain shape-associated genes (LOC_Os06g14260 and LOC_Os04g51950). Our findings uncover multiple grain shape heterosis-related loci and provides a new insight into heterosis mechanism of grain shape in rice.