Improving Heat Tolerance of Wheat By Combining Genomic, Molecular and Physiological Approaches.

Climate change, particularly the heat stress, poses a serious challenge to the wheat production, which needs to double by 2050 in order to meet the food demand of the growing population. Every 1°C rise in temperature above the optimal results in wheat yield losses of up to 3-4%. By the end of the 21^st century, global annual mean temperature including South Asia is projected to go up by 4°C, thus adversely affecting the wheat production in most of fertile Indo-Gangetic plains. Therefore, improving wheat heat tolerance is crucial in today’s context. As a public-private partnership, ‘Feed the Future Innovation Lab’ has been setup with the funding from USAID, DBT, ICAR, and BIRAC with a goal to develop climate resilient wheat cultivars by combining all available information, tools, and technologies. Evaluation of heat tolerant material from around the globe both under controlled as well as field conditions showed extensive natural variation for the trait, although, only few lines maintained ‘normal’ productivity at 30^oC. A short period of heat stress during germination had serious and long-term effect on plant development and yield. A ten-day heat stress at germination reduced germination percentage, coleoptile length, and yield. Sugars availability maybe a reason for the effect on germination as external application of sucrose showed significant recovery in germination percentage and coleoptile length. Heat stress during vegetative phase significantly affected tiller number, flowering time, pollen fertility, plant height and yield. During the reproductive stage, heat stress adversely affected photosynthesis and increased membrane disintegration due to decreased chlorophyll index, increased ROS and lipid peroxidase activity. The identified heat tolerant lines will be used to transfer the trait into wheat cultivars by marker assisted background selection combined with simultaneous detection and utilization of QTLs. Various molecular and physiological studies for the trait are underway and update will be presented.