Genetic variation and correlations among physiological characters in Indian mustard (Brassica juncea L.) under high temperature stress

Effects of high temperature stress during terminal stage on crop growth and genetic parameters were investigated in 18 advanced breeding lines and 4 varieties of Indian mustard [Brassica juncea (L.) Czernj. & Cosson] under normal (E-1) and late sown (E-2) conditions. Genotypes BPR 538-10 showed terminal heat tolerance for biological yield/plant, seed yield/plant, total dry matter (60 days after sowing (DAS), crop growth rate (CGR) and relative growth rate (40-60 DAS) and heat use efficiency while RH 0216 possessed terminal heat stress tolerance only for biological yield/plant. Terminal heat stress decreased heat use efficiency by 16.1% in BPR-538-10 to 66.3% in BPR-327-1-B. Heat use efficiency had high PCV and moderate GCV under E-1. The seed yield/plant exhibited significant and positive association with leaf area index (LAI) at 40 days after sowing (r= 0.434*, CGR during 40-60 DAS (r = 0.59**), total dry matter at 60 DAS (r = 0.590**), and heat use efficiency (0.795**) under high temperature stress. The study suggested that rapid leaf area development resulting in to high total dry matter production is vital for developing suitable varieties against terminal heat stress.