Screening of Indian mustard (Brassica juncea) for thermo tolerance at seedling and terminal stages

Abstract

Effect of heat stress was visualized at seedling stage in terms of seedling mortality and at terminal stage on
growth traits and yield in 25 promising mustard (Brassica juncea L.) genotypes grown in randomized block
design with three replications in two environments viz. timely (3rd week of October) and late sown (3rd week
of November). Genotypes RB-10, PR-2004-2, NPJ-93, NRCDR-2, CS-810-5-2-SP showed >30% seedling
mortality and were rated as thermo tolerant. Significant genotypic differences existed for all growth traits at
two sowing dates, and environment had a profound impact not only on morphological traits but also on the
reproductive behavior and seed filling which in turn was associated with yield reduction under terminal heat
stress. Two genotypes RL-2047 and RGN-152 registered yield reduction less than 30%in the present
investigation.RL-2047 showed terminal heat tolerance for seed yield/plant and was moderately tolerant for
biological yield/ plant, seeds/siliqua, and siliqua length while RGN-152 possessed terminal heat stress
tolerance only for biological yield/plant in addition to moderate tolerance for siliquae on main shoot, and siliqua
length. Seed yield/plant exhibited significant and positive association with heat susceptible index (HSI, r=0.58*),
and negative association with heat tolerance efficiency (HTE, r=-0.57*) in the timely sown cultivars.
Reverse association was found under high temperature stress with delayed sowing. Furthermore, average
heat susceptible index (HSI) was 0.28 and heat tolerance efficiency (HTE) was 84.8 % in the resistant
genotypes. Heat tolerance parameters studied in this investigation may be used for screening traits, and the
identified genotypes as suitable donor for crossing programmes to develop heat tolerant mustard genotypes.