Response of Food Grain Crops to Changing Environments.

Crop production is highly sensitive to changing environmental conditions. In recent years’ long-term climate change and year-to-year climate variability has become a major challenge to crop productivity. Current knowledge on effects of season-long high temperatures and elevated carbon dioxide concentrations; and effects of short periods of high temperature stress on various physiological, growth and yield processes will be presented and discussed. Main focus will be on major grain crops (rice, wheat, sorghum, groundnut). Results indicate that above optimum temperatures will have negative impacts on reproductive processes (such as pollen production, pollen germination, fertilization, seed numbers and individual seed weight) resulting in lower seed yield. The beneficial effects of elevated carbon dioxide mediated through increased photosynthesis will be negated by rising temperatures resulting in lower seed yields. Grain crops are most sensitive to high temperature stress during gametogenesis and flowering. High temperature stress during these stages leads to loss of gamete fertility, poor pollination, decreased fertilization and embryo abortion resulting in fewer seed numbers. Development of high temperature tolerant cultivars will be of prime importance for adaptation to climate change and climate variability. Genetic variability exists for high temperature tolerance in grain crops. Some physiological traits that may contribute to high temperature tolerance include increased membrane thermostability, increased green leaf duration, canopy temperature depression, optimum respiration, higher reproductive fertility, early morning flowering, and faster and/or longer grain filling period. New emerging biochemical and molecular tools provides some opportunities for screening and phenotyping. Continued collaboration between physiologists, breeders, molecular biologists and agronomists is essential for developing strategies to combat effects of changing environments and management practices on crop production.