LAUSR

Photosynthetic traits can sense and signal abiotic stress at early growth stages of mustard [Brassica juncea (L.) Czern & Coss]. The integration stress responses with multiple selection indices can select the fittest/tolerant genotypes. With this goal, a set of 210 diverse mustard genotypes were phenotyped under control and salt‐stress (electrical conductivity = 12 dS m−1). Significant dynamic response of the plant to salt stress with reduction for all morpho‐physiological traits and genotype × treatment interaction was observed under salinity. A higher accumulation of Na+ was recorded in the roots, followed by shoots. A close correspondence between phenotypic coefficient of variation and genotypic coefficient of variation under control and salt stress conditions results in high heritability (h2) in broad sense. A significant negative association between shoot and root Na+ content and rate of photosynthesis also indicated that Na+ was significantly restricted in the root. This was not found to be efficient because considerable Na+ buildup was observed in the shoot. Multiple trait‐based indices, such as membership function value of salinity tolerance, classical Smith–Hazel index, factor analysis ideotype–best linear unbiased prediction index, and multi‐trait genotype‐ideotype distance index, deduced CS 2009‐159, CS 2009‐420, CS 2009‐124, and Swarn Jyoti (RH‐9801) are promising for identifying salt‐tolerant genotypes that can serve as donors for the development of salt‐tolerant cultivars.