Evaluating biochemical traits and genetic parameters as selection criteria for salinity tolerance in Nigella sativa L.

The present investigation was conducted to assess the performance of a high-yielding line (AN-1) of Nigella sativa under six NaCl levels (0, 5, 10, 20, 50, and 100 mM) over two crop seasons. Data were recorded for seed yield and eight contributing traits, viz., chlorophyll a, chlorophyll b, carotenoids, phenolics, flavonoids, protein content, catalase, and peroxidase activity. Fundamental statistical measures, including mean, standard error, variance, and coefficient of variation, were investigated along with broad-sense heritability and genetic advance. The data were also analyzed using principal component analysis (PCA), correlation analysis, and path coefficient analysis. Seed yield increased at 10 mM salt concentration and was 26% higher than the control, but thereafter decreased. Protein content increased by 23% at 100 mM. At 50mM, peroxidase (maximum: +47.78%) reached a peak; catalase increased till 50mM but decreased at 100mM. The top two PCs explained > 73% of the variance, with the variance dominated by peroxidase/flavonoids (+) and chlorophyll a/carotenoids (−). The genotypic coefficient of variation (GCV) and genetic advance were highest in peroxidase, catalase, and seed yield, while broad-sense heritability was high across all traits. Chlorophyll b was the only pigment that showed high GCV, heritability, and genetic advance, along with a significant positive correlation with yield. Path analysis indicated that the direct positive contributions came from flavonoids, catalase, and chlorophyll b. Catalase, peroxidase, and chlorophyll b exhibited high GCV, heritability, and genetic advance in both experimental years, which indicated that these traits are under genotypic control and should be utilized in selection programs to enhance yield on soils with low to moderate salinity.