Response of tomato and squash genotypes to salinity stress at the vegetative stage under controlled greenhouse conditions

Salinity stress is a major abiotic constraint in vegetable production, causing substantial yield losses. Cultivating salt-tolerant varieties offers a sustainable strategy to mitigate these impacts. In the present study, 30 tomato (Solanum lycopersicum L.) and 32 squash (Cucurbita spp.) cultivars commercially grown in Florida were evaluated under greenhouse conditions to assess their responses to varying salt levels (0, 100, 150 and 200 mM/L NaCl). The experiment was conducted in a completely randomized block design with three replicates per cultivar and salt treatments were applied for 2 h every alternate day, starting from the second true leaf stage. Plant responses were assessed by measuring chlorophyll content [7 and 14 days after treatment (DAT)], shoot length (14 DAT), and biomass (14 DAT). In tomato, chlorophyll content declined with increasing salt concentration, whereas in squash, it showed a positive correlation with salt concentration. The observed increase in chlorophyll levels under stress conditions suggests a potential link between salinity stress and the chlorophyll biosynthesis pathway. In both crops, an inverse relationship between plant growth (shoot length and biomass) and salinity stress was observed. Hierarchical clustering based on percentage change in shoot length and biomass classified the genotypes into four distinct groups, with twelve tomato and seven squash genotypes clustering into the highly salt tolerant cluster. These results provide preliminary insights into genotype specific responses to salinity at the vegetative stage under greenhouse conditions. However, further validation under field condition is required to verify their broader applicability and to better understand the underlying physiological and molecular mechanisms of salt stress tolerance.