Genetic study of terminal heat stress in indigenous collections of Indian mustard (Brassica juncea L.) germplasm

Aim: The present study was carried out to evaluate 145 genotypes of Indian mustard for terminal heat stress under late sown irrigated conditions. Methodology: One hundred and forty five genotypes of Indian mustard were evaluated for terminal heat tolerance, along with six checks in augmented block design. The effect of heat stress was assessed on different agro-morphological traits. Data were recorded on five randomly selected plants for 12 different quantitative traits for each genotype. Results: Terminal heat stress caused significant reduction in performance of all traits, except oil content and fruiting zone length. Seed yield per plant showed highest reduction (33.92%) followed by 1000-seed weight (21.28%). Thousand-seed weight and secondary branches per plant were found associated with seed yield under late sown conditions. Based on yield under stress, yield index, geometric mean productivity and stress tolerance indices, five lines viz., DRMR-59, DRMR- 2094, DRMR- 2129, DRMR-2071, DRMR-2136 were identified as high yielding and terminal heat stress tolerant. Whereas, based on heat stress susceptibility index, DRMR-1347, DRMR-1154, DRMR-1190 were top performing lines tolerant to terminal heat stress. Interpretation: Selection of high yielding lines under stress condition can be done using correlated traits. Yield under stress was found significantly correlated with YSI, YI, MP, STI and GMP suggesting to use these indices for selection of high yielding and heat tolerant lines. However, further revalidation is very much needed for effective use of these indices for selection of heat tolerant lines in Indian mustard.