Genetic Variability and Temperature Stress Response of Indian Mustard (Brassica juncea L.) under Early and Timely Sowing Environment in Doon Valley

Abstract

Aims: The study evaluates genetic variability in response to temperature stress under early- and timely-sown conditions in the Doon Valley, Uttarakhand, India. Study Design: The field tests employed an Augmented Randomized Complete Block Design (ARCBD) featuring two sowing conditions in pots. Place and Duration of Study: The study took place at the Jigyasa University campus in the Doon Valley, Uttarakhand, India, during the 2023–24 Rabi season. Methodology: 100 genotypes of Indian mustard were planted in pots using an Augmented Randomised Complete Block Design. The pots were placed in two different sowing environments: early and timely sowing. In five blocks, 95 of the 100 Indian mustard genotypes were planted as test treatments and 5 as check treatments. All blocks were treated identically in both sowing settings. Along with temperature, data on morphological, phenological, yield, and physiological traits were regularly recorded. After harvesting, statistical tests were performed to examine PCV, GCV, ECV, hBS, and GAM. Results: The study indicated significant genetic variability among 100 Indian mustard genotypes studied under early (ES) and timely sowing (TS) environments in the Doon Valley. Treatment-adjusted and block-adjusted ANOVA indicated highly significant (P ≤ 0.01) differences for most morphological, yield, and physiological traits in both environments. Silique per plant (SPP), seed yield per plant (SYP), oil yield per plant (OYP), harvest index (HI), and membrane stability index (MSI) exhibited high genotypic (GCV > 20%) and phenotypic (PCV > 20%) coefficients of variation coupled with high heritability (>80%) and high genetic advance (>40%), indicating strong additive gene action. Early sowing conditions maintained uniformity, whereas timely sowing showed comparatively higher variability (CV up to 7.08% for SYP). Oil content (%) remained non-significant in ANOVA and showed low GCV (0.48%) under ES, indicating limited genetic variability, though improved expression was observed under TS. Physiological traits such as MSI and RWC demonstrated significant variability, confirming differential thermo-tolerance among genotypes. Conclusion: The findings confirm the presence of available genetic variability for yield and stress-related traits under both sowing environments. Traits such as SPP, SYP, OYP, HI, SMS, and MSI exhibited high heritability and genetic advance, suggesting the significance of additive gene action and suitability for direct selection. Early sowing effectively distinguished genotypes under mild heat stress, while timely sowing reflected greater phenotypic expression under temperature variation. Oil content showed comparatively narrow variability, indicating the need for targeted breeding approaches. Overall, multi-environment evaluation proved essential for identifying stable, high-yielding, and temperature-resilient genotypes suitable for climate-adaptive mustard breeding programs in the Doon Valley.