Temperature induction response and accumulation of starch granules as indices to identify the thermotolerance of pulses at early growth stages

In pulses, high temperature is a major limiting factor for yield decline. Tamil Nadu has a rich pulse germplasm with high genetic variability. Hence, the present study was designed to develop a technique to screen genotypes for high temperature tolerance. Arapid screening protocol was developed based on the principle of “acquired tolerance”. Adapting this temperature induction response (TIR) technique to pulses, popular varieties of TNAU pulses of blackgram (VBG-07-001, VBG-08003), redgram (CO-6, VBN-2) and soybean (CO-1, CO-2) were screened for thermotolerance. The challenging lethal temperature was standardized as 50°C for 3 hours at which 90 per cent of the seedling mortality occured. The induction temperature was standardized as 36°C to 40°C at which 48.3 per cent of growth reduction over control was noticed. Blackgram showed higher thermotolerance than other pulses in terms of survival percentage and seedling growth. Blackgram seeds showing contrasting behaviour to temperature stress tolerance namely VBG-07-001(tolerant) and VBG-08-003 (susceptible) were analysed for the accumulation and distribution of starch granules responsible for the grain filling under heat stress.