Rice Races Against Rising Temperatures - Achievements, Opportunities and Challenges.

Rice races against rising temperatures - achievements, opportunities and challenges

Krishna Jagadish S.V.*, Tsutomo Ishimaru, Changrong Ye

Higher probability of occurrence of more intense and frequent heat stress episodes and extended warmer nights in the future are major challenges towards sustaining rice production. Although heat stress affects rice crop at different growth and developmental stages, it is highly vulnerable to heat stress during the gametogenesis and the flowering stages. Short duration heat stress during the day coinciding with either gametogenesis or anthesis leads to negative impact on seed-set, while longer stress exposure during post-anthesis decreases seed filling duration leading to decreased seed weight. Extensive research efforts has allowed us to map heat tolerant QTL, develop NILs (near isogenic lines) which can potentially reduce the spikelet sterility by up to 15%. An alternative route to minimize heat stress damage in rice is by exploiting the early morning flowering trait, which was identified and introgressed from wild relative Oryza officinalis. NILs for this trait have been developed in both indica and japonica backgrounds, having the potential to reduce sterility by about 20%, with the advantage increasing with severity of stress. We are currently in the process of combining these two physiological traits into single genetic background and the initial results obtained will be presented. Interestingly, the rapid increase in minimum night temperature reduces diurnal amplitude inducing an alternative physiological route to increase yield and grain quality losses compared to heat stress during the day. This phenomena will be compared across studies carried out under controlled environments and field conditions, with an emphasis on the night respiration and carbon balance. Currently, we are in the process of defining the critical nigh temperature thresholds inducing yield and quality losses under field conditions. Research progress achieved over the last decade through a multi-disciplinary and multi-institutional collaborative efforts, unaddressed challenges and future direction of rice heat stress research will be highlighted.