Loss of starch synthase IIa alleviates the negative impact of high temperature on rice starch during grain filling

Summary

This study demonstrates that introducing a functional mutation in starch synthase IIa (ss2a) in rice can genetically compensate for the negative effects of high temperatures during grain filling. Under heat stress, normal rice plants show reduced amylose and increased long-chain amylopectin, degrading eating quality; the ss2a mutation increases short amylopectin chains to counteract this response. Field trials at two Japanese locations with contrasting temperatures confirmed that the mutation maintains desirable starch structure and eating quality across temperature conditions, offering a breeding target for climate-resilient rice cultivars.

Regional applicability

This research is directly relevant to United Kingdom agriculture given projected increases in summer temperatures during grain-filling periods for any rice cultivation (though rice is not a major UK crop). The breeding principle—introducing specific mutations to confer heat resilience whilst maintaining nutritional and quality traits—is transferable to other cereals (wheat, barley) grown in the UK, particularly as climate change intensifies heat stress during critical phenological stages.

Key measures

Grain traits, starch structure (amylose content, amylopectin chain-length distribution, short and long amylopectin chains), eating quality

Outcomes reported

The study evaluated how starch synthase IIa (SSIIa) mutation affects starch structure and eating quality in rice grown under contrasting temperature regimes during grain filling. Rice lines with the ss2a mutation showed increased short amylopectin chains and apparent amylose content, with temperature-dependent effects on eating quality.

Topic tags