<i>gw2</i> mutation increases grain width and culm thickness in rice (<i>Oryza sativa</i> L.)

Abstract

Grain size is one of the most important agricultural traits in rice. To increase grain yield, we screened a large grain mutant from mutants with the 'Koshihikari' background. As a result, we obtained a mutant, KEMS39, that has a large grain size and increased yield. Cultivation tests revealed that this mutant had improved lodging resistance with thicker internodes. Next-generation sequencing analysis revealed the presence of a 67 bp deletion in the <i>GW2</i> mRNA, owing to a mutation in the 3' splice site of the sixth intron of the <i>GW2</i> gene. To determine whether this mutation was responsible for the larger grain and thicker internodes, we performed gene editing and obtained a mutant with a 7 bp deletion, including this 3' splice site. As this <i>gw2</i> mutant had large grains and thicker internodes, the causal gene of KEMS39 was determined as <i>GW2</i>. Thicker internodes are attributed to the pleiotropic effect of <i>gw2</i> mutation. On the basis of these results, we conclude that <i>gw2</i> mutation has the potential to be an important genetic resource with the ability to achieve a well-balanced and high-yielding effect that simultaneously improves grain productivity and lodging resistance.