Salicylic acid and kinetin mediated stimulation of salt tolerance in cucumber (Cucumis sativus L.) genotypes varying in salinity tolerance

Greenhouse studies were undertaken to evaluate the genetic performance of two cucumber genotypes (Long Green and Summer Green) at four salinity levels (0, 25, 50, and 100 mM NaCl). Seeds were pretreated with 50 mg salicylic acid (SA) L-1 and 25 mg kinetin (Kin) L-1. Under hydroponic conditions, seed pretreatment with Kin significantly increased shoot and root dry biomass and reduced the salt injury index in both genotypes. SA reduced the salt injury index of Long Green cucumbers. In a pot experiment, Kin treatment reduced Na+ and increased K+ concentration, photosynthesis, and chlorophyll content in both genotypes, compared to SA under saline soil conditions. Kin treatment improved fruit yield in both genotypes, while SA had a statistically significant effect on Long Green fruit yield. The application of SA and Kin enhanced salinity tolerance in both genotypes by the activation of antioxidants, especially superoxide dismutase, peroxidase, and catalase, which offset oxidative injury. Summer Green exhibited better salt tolerance and improved osmoregulation that resulted in higher fruit yield than Long Green. It was concluded that cucumber genotypes differed in salt tolerance, and seed pre-treatment with Kin minimized salt stress injury, even in sensitive genotype which could sustain crop production under saline conditions.