Carbon dioxide responsiveness mitigates rice yield loss under high night temperature

Increasing night-time temperatures are a major threat to sustaining global rice (Oryza sativa L.) production. A simultaneous increase in [CO(2)] will lead to an inevitable interaction between elevated [CO(2)] (e[CO(2)]) and high night temperature (HNT) under current and future climates. Here, we conducted field experiments to identify [CO(2)] responsiveness from a diverse indica panel comprising 194 genotypes under different planting geometries in 2016. Twenty-three different genotypes were tested under different planting geometries and e[CO(2)] using a free-air [CO(2)] enrichment facility in 2017. The most promising genotypes and positive and negative controls were tested under HNT and e[CO(2)] + HNT in 2018. [CO(2)] responsiveness, measured as a composite response index on different yield components, grain yield, and photosynthesis, revealed a strong relationship (R(2) = 0.71) between low planting density and e[CO(2)]. The most promising genotypes revealed significantly lower (P < 0.001) impact of HNT in high [CO(2)] responsive (HCR) genotypes compared to the least [CO(2)] responsive genotype. [CO(2)] responsiveness was the major driver determining grain yield and related components in HCR genotypes with a negligible yield loss under HNT. A systematic investigation highlighted that active selection and breeding for [CO(2)] responsiveness can lead to maintained carbon balance and compensate for HNT-induced yield losses in rice and potentially other C(3) crops under current and future warmer climates.