A deletion in a single gene promotes increased grain size and yield in rice, according to a study published online this week in Nature Genetics. The identification of this deletion may enable a breeding program for higher-yield cultivated rice crops.
Takeshi Izawa and colleagues carried out a cross between the Nipponbare (japonica) and Kasalath (indica) cultivated crops, which have different grain widths. They mapped several regions of the rice genome that were associated with this difference, and focused on one, qSW5. They went on to identify a deletion in a single gene in the Nipponbare cultivation, which is responsible for approximately 38% of the difference in grain width between Nipponbare and Kasalath.
Transgenic lines of Kasalath rice engineered to have reduced levels of qSW5 produced seeds with increased grain weight in a field test. The authors suggest that the qSW5 deletion may have been selected for during the process of rice domestication by ancient humans. They also report that two other genes, Waxy and qSH1, were likely also involved in the domestication of japonica rice as the range of rice cultivation changed during human history.