Physiological and candidate gene analysis of <i>RG5</i>, a locus associated with a higher ratio of filled grains in rice (<i>Oryza sativa</i> L.)

In this report, we investigated physiological and genetic aspect of <i>RG5</i>, a locus increasing the ratio of filled grain in rice (<i>Oryza sativa L)</i>. <i>RG5</i> increased the accumulation of non-structural carbohydrates (NSCs) in the body, and NSCs might contribute to the development of grains after heading. With a chromosome segment substitution line containing ‘Kasalath’ <i>RG5</i> in the genetic background of the <i>japonica</i> cultivar ‘Koshihikari’, <i>RG5</i> might enlarge lower leaves and improve NSC supply to the sheath. Through the fine mapping using data plural mutans, we identified <i>NBS-LRR protein</i> (Os05g0380300) as a casual gene for expanding of lower leaves area by <i>RG5</i>. The single nucleotide polymorphism (SNP) of Kasalath caused a premature stop codon and lost function might increase the ratio of filled grains.