Genetic analysis of heat stress tolerance in Indian mustard (Brassica juncea)

A set of 53 Indian mustard [Brassica juncea (L) Czern and Coss] genotypes were evaluated for genetic variability and correlation for yield and physiological characters during the rabi season of 2012-13 and 2013-14 under heat stress (early sown) and normal (timely sown) environmental conditions. The study was undertaken to generate genetic information for seed yield/plant (g), population survival (%) at 10 and 25 days after sowing (DAS), membrane stability index (MSI) (%), excised-leaf water loss (%), relative water content (%), water retention capacity of leaves (%), 1000-seed weight (g) and oil content (%). Moreover, magnitude of relationships among these characters were also measured. Significant differences were observed for all the characters among the genotypes, except 1000-seed weight, which revealed the presence of sufficient variability for the characters. The phenotypic coefficient of variation (PCV) for all the characters were found to be higher than genotypic coefficient of variation (GCV). High PCV for MSI, seed yield/plant and population survival (PS) at 25 DAS obtained in the study showed the significance of additive genes. High heritability estimates coupled with high to moderate genetic advance as per cent of mean was recorded for PS at 25 DAS, WRCL and RWC indicating the significance of additive genes and the role of additive gene action for the inheritance of these characters. Moreover; it also became evident that selection may be performed for the improvement in these characters. Among the different characters oil content recorded low heritability estimates along with low genetic advance. Low heritability estimate for oil content indicated the predominance of non-additive gene effects for this trait and thus the scope of its improvement through selection might be very low. However, it may be improved through hybridization. Character association studies revealed that seed yield/plant and RWC are highly positive correlated (r=0.407**) which could be considered as one of the important selection criteria in the improvement of seed yield under heat stress situation. Adequate genetic variability was present within available Indian mustard genotypes to allow breeding improvement of seed yield and physiological characters.