Integrated Phenotypic and SSR-Based Characterization of Drought-Tolerant Tomato (Solanum lycopersicum L.) Genotypes in the Arid Region of Balochistan, Pakistan

Drought stress is one of the most critical abiotic factors limiting tomato (Solanum lycopersicum L.) productivity worldwide, particularly in arid and semi-arid regions such as Balochistan, Pakistan. The present study aimed to identify drought-tolerant tomato genotypes using integrated phenotypic and molecular approaches. A total of forty-five tomato genotypes with diverse genetic backgrounds were evaluated under control and drought stress conditions in a completely randomized design with three replications. Plants were grown under optimal irrigation for eight weeks, after which drought stress was imposed by withholding irrigation for ten days. Data were recorded for key physio-morphological traits including plant height, relative water content, plant biomass, and chlorophyll content. Significant variation was observed among genotypes under both normal and drought conditions, with plant biomass showing the highest variability. Principal component analysis (PCA) identified five genotypes Tom/Sl/Na/22, Rio Grande, Tom/Cr/Pr/07, Bolan, and Hellfurtc as drought tolerant based on their superior performance under stress conditions. For molecular characterization, fifteen simple sequence repeat (SSR) markers were used for DNA fingerprinting. Twelve markers exhibited polymorphism, one marker produced monomorphic bands, and two markers failed to amplify. Cluster analysis using the UPGMA method grouped the genotypes into four major clusters. Notably, drought-tolerant and susceptible genotypes identified through phenotypic evaluation were clearly separated in the phylogenetic tree, indicating consistency between phenotypic and molecular analyses. The identified drought-tolerant genotypes represent valuable genetic resources for developing drought-resilient tomato cultivars through breeding programs.