RESUMO
Pulses have been described as a "poor man's meat and affluent man's vegetable" in India. Chickpea (Cicer arietinum L.) is the third most legume crop grown during rabi season under receding soil moisture. Chickpeas is known to flourish in drought-prone conditions, but it seems to be sensitive to heat stress exceptionally during reproductive development, resulting in considerable yield loss. The performance of chickpeas under heat stress is more variable. It is crucial to develop screening tools to identify thermotolerant chickpea genotypes because of the increase in average global temperatures. In this view, a lab experiment was conducted to standardize the temperature induction response (TIR) protocol for chickpea seeds. The 70 % hydrated seeds were used for the experiment. This technique can be used as a potential tool to identify and select temperature tolerant lines at the seed stage itself from a large population. A set of six chickpea genotypes were screened for intrinsic tolerance using the standardized Thermo Induced Response (TIR) protocol. Among the genotypes JG-14, JG-11 and A-1 showed highest thermo tolerance in terms of higher survival of seeds (germination percentage) and seedlings with less per cent reduction in seedling survival, root and shoot growth. The genotypes with intrinsic heat tolerance can be explored for the development of varieties suitable for late sown conditions in Karnataka where chickpea is prone to terminal heat stress. The results of the study concluded and standardized the sub lethal temperature as 32 ºC to 50 ºC for 5 hours and 30 min, lethal temperature i.e., challenging temperature as 58 ? for 3 hours and LD 50 as 52 ? for 3 hours at seed level itself.
RESUMO
Global warming is a never-ending disastrous threat to the world and the existence of life. For many years, researchers have been cautioning about the disastrous results on the climate if the world touches average temperatures of 1.5ºC above the pre-industrial levels. High-temperature stress affects the growth and development of crops, Reduced photosynthesis and transpiration lead to lower biomass and increased respiration, leading to faster depletion of stored carbohydrates and reduced growth. Altered mineral nutrition and enzyme activity leads to nutrient imbalance and oxidative stress and eventually lowers yields to significant levels. Thermotolerance is a complex trait, and along with agronomic practices, there is a need for the identification and characterization of genotypes for heat tolerance, which is a prerequisite for crop improvement. Temperature Induction Response (TIR) is a high-throughput means successfully employed for assessing, identifying, and screening crop plants for thermotolerance in different crop species. TIR is based on the principle of the LD50 concept and acquired thermotolerance, which is crop-specific in nature. Hence, this review focuses on the relevance, methodology, standardization, mechanism, utilisation and significance of the TIR technique for crop improvement in different crop species to combat heat stress.