In the era of global warming, heat stress, particularly at the seedling stage, is a major problem that affects the production and productivity of crops such as mustard that are grown in cooler climates. Nineteen mustard cultivars were exposed to contrasting temperature regimes—20 °C, 30 °C, 40 °C and a variable range of 25–40 °C—and evaluated for changes in physiological and biochemical parameters at the seedling stage to study their role in heat-stress tolerance. Exposure to heat stress showed detrimental effects on seedling growth as revealed by reduced vigor indices, survival percentages, antioxidant activity and proline content. The cultivars were grouped into tolerant, moderately tolerant and susceptible based on the survival percentage and biochemical parameters. All the conventional and three single-zero cultivars were found to be tolerant and moderately tolerant, respectively, while double-zero cultivars were reckoned to be susceptible except for two cultivars. Significant increases in proline content and catalase and peroxidase activities were found associated with thermo-tolerant cultivars. More efficient antioxidant system activity and proline accumulation were noticed in conventional along with three single-zero (PM-21, PM-22, PM-30) and two double-zero (JC-21, JC-33) cultivars that might have provided better protection to them under heat stress than the remaining one single- and nine double-zero cultivars. Tolerant cultivars also resulted in significantly higher values of most of the yield attributing traits. Heat-stress-tolerant cultivars could easily be selected based on the survival percentage, proline and antioxidants at the seedling stage and included as efficient cultivars in breeding programs.

The effects of early and late sowings were studied on Indian mustard cultivars. During the years 2021-22, the 8 genotypes were cultivated in RBD with 3 replications on three sowing dates: September (D1 ), October (D2 ), and November (D3 ) at SST, IARI, and New Delhi. Sowing dates were found to be significant for all of the characters, although genotypes and their interactions were only significant for a no. of seeds per siliqua studied. The results revealed that the timely sown condition (D2 ) was found to be better for all genotypes. Among the eight genotypes, JC-33 had a maximum no. of seeds per siliqua in timely sown condition (D2). It was discovered that the sowing date influenced yield characteristics significantly. As the sowing date was extended, the seed yield was found to decline dramatically.