How rising temperatures would be detrimental for cool and warm-season food legumes

Rising temperatures are a major concern for the productivity of
\nfood legumes, grown in winter as well as summer-season, especially
\nin tropical and sub-tropical regions. Our studies have
\nindicated marked damage to the reproductive stage, resulting in
\nreduction in pod set and seed yield of chickpea, lentil (cool-season
\nlegumes) and mungbean (warm-season legume) under high
\ntemperatures. Studies done in controlled and outdoor environments
\n(late sowing) revealed that temperatures >35/20°C (as
\nday and night) were highly detrimental for winter-season legumes;
\nwhile >38/25°C markedly affected the summer-season
\nlegumes (mungbean). Urdbean, (a summer season legume),
\nwas found to be relatively more tolerant. The degree of damage
\nvaries depending upon the duration, timing and severity
\nof stress. Among the reproductive components, pollen grains
\nwere more sensitive, became deformed and showed reduction
\nin pollen viability, reduced germination and pollen tube growth.
\nStigma receptivity and ovule viability were also inhibited, which
\naffected the pollen germination on stigma surface and restricted
\ntube growth through style, and impaired fertilization to cause
\nflower abortion. Assessment of the physiology of leaves, anthers
\nand styles indicated decrease in sucrose production in all these
\norgans due to inhibition of enzymes, which possibly affected the
\nstructural and functional aspects of the pollen grains and tube
\ngrowth through style. Seed filling is another stage which becomes
\nimpaired as a result of inactivation of enzymes related to
\nsucrose production, causing inhibition in sucrose translocation
\ninto seeds. Additionally, the composition of the seeds was adversely
\naffected, resulting in small size and poor quality of seeds.
\nThe data related to these processes would be presented. Genetic
\nvariation for heat tolerance exists in our target legume crops,
\nwhich needs further probing and use of heat tolerant germplasm
\nin breeding programs. Screening for high temperature tolerance
\nhas led to identification of few heat-tolerant genotypes, which
\nare able to maintain their gamete function at high temperature,
\nunlike the sensitive genotypes. Future studies should focus on
\nhigh throughput phenotyping techniques and/or physiological,
\nbiochemical or genetic markers that control the reproductive
\nfunction. Information about the effects of heat stress on reproductive
\nbiology and seed filling events of chickpea, lentil and
\nmungbean will be discussed.