Accelerated mustard [Brassica juncea (L.) Czern & Coss] improvement for salt tolerance: Photosynthetic traits and selection indices

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.