Enhancing salt tolerance and yield potential in cotton: insights from physiological responses, genetic variability, and heterosis

Soil salinity is a growing global concern, necessitating the development of salt-tolerant cotton cultivars to enhance the utilization of salt-affected soils and boost crop productivity. Salt tolerance is regulated by a complex interplay of genetic and physiological factors involving multiple genes. To investigate the genetic basis of salt stress tolerance, eight parental genotypes (four lines and four testers) and their 16 hybrid combinations were evaluated under normal and salt stress conditions (15 dS m-1). Data were collected on various traits including the plant height (PH), number of bolls per plant (NBP), boll weight (BW), lint percentage (LP), seed cotton yield (SCY), fiber length (FL), fiber strength (FS), fiber fineness (FF), chlorophyll a and b, carotenoids (CAR), total soluble proteins (TSP), hydrogen peroxide (H2O2), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), potassium ions (K+), sodium ions (Na+), and K+ to Na+ ratio (K+/Na+). The box plot analysis indicated that the median values of the morphological and fiber traits were reduced under salt stress, with the exception of the FF and Na+, which increased. Antioxidant molecule levels were significantly elevated against salt stress, while the ionic and physiological traits decreased. The line x tester analysis revealed significant genetic variation among the genotypes for all the traits, with the testers contributing more to the variation than the lines and their interactions. Nonadditive gene action predominated for most of the morphological, physiochemical, and ionic traits, as indicated by the higher specific combining ability (SCA) effects compared to the general combining ability(GCA) effects under both conditions. Notably, the genotypes, Barani-333 and JSQ-White Hold, were identified as good general combiners. Cross combinations FBG-222 x Barani-222, Hatf-3 x CCB-17, and CCB-22 x JSQ-White Hold, exhibited desirable SCA effects and superior parent heterosis for most of the traits under both conditions. The identified parents and cross combinations showed potential for breeding programs aimed at developing salt-tolerant cultivars.