CRISPR/Cas9 based modulation of V-PPase expression in rice improves grain quality and yield under high nighttime temperature

Warming trend of the climate has been linked with yield losses in many crops. Like other cereals, rice is highly sensitive to above-typical temperatures during reproductive and grain filling stages. In fact, nighttime temperatures have risen faster than daytime temperatures in many parts of the world. For this reason, rice studies in recent years have focused on the effect of high nighttime temperature (HNT) on grain yield. Several studies have shown that HNT disturbs key processes in reproductive development and grain filling that lead to reduced spikelet fertility (SF) and enhanced grain chalkiness (Srivastava et al., 2024). Chalkiness is the opaque area on the grain, and it is not just an appearance issue, it also impacts milling quality. Above the generally acceptable chalk values (6-10%), every 1% increase in chalkiness leads to 1% decline in head rice yield (HRY) (Zhao and Fitzgerald 2013). Therefore, breeding HNT tolerance is vital for safeguarding grain yields from heat waves in the future. However, breeding efforts have been impeded by the lack of reliable tolerance alleles in modern cultivars. Breeding is also complicated by the complex nature of HNT tolerance as not only SF and grain quality traits, but other yield components such as panicle length, grain width, grain size, and grain weight are also affected by HNT in a genotype-dependent manner. Not surprising, hundreds of QTLs have been identified in the genomics studies. Of which, Chalk5 (Os05g0156900) is most notable as it stands as one of the few functionally validated QTL (Fan et al., 2024; Gann et al., 2023; Li et al., 2014).