A Study about Temperature Induction Response (TIR): Novel Physiological Approach for Thermotolerant Genotypes in Chickpea (Cicer arietinum L.)

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.