Genetic Diversity and Drought Tolerance in M7 Ethidium Bromide-Derived Tomato Genotypes

Abstract

This study evaluated the extent of genetic variability for drought tolerance, as well as the interplay among key drought-tolerant traits of M7 ethidium bromide (EtBr)-derived tomato genotypes, under polyethylene glycol (PEG)-induced drought stress. The study assessed ten of tomato genotypes under varying PEG concentrations (0%, 5%, and 10%) using a Completely Randomized Design. Statistical analysis was conducted on data including germination capacity and energy, root length, root count, shoot length, and both fresh and dry shoot weight. ANOVA revealed significant variability among genotypes for all traits. Higher concentrations of PEG led to reduced germination and weaker seedling performance. However, genotypes G3, G8, G9, and G10 exhibited superior drought tolerance, as reflected in their extensive root development. Based on Stress Tolerance Indices (STIs), genotypes G2, G3, G8, G9, and G10 were effectively ranked as highly drought-tolerant. High phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV) (>20%), and heritability (>60%) were observed for germination energy and capacity, root count, and fresh shoot weight. Consistent correlations were observed between germination capacity and traits such as shoot height and root length. The study reveals substantial genetic variability among EtBr-derived tomato genotypes, with G3, G8, G9, and G10 exhibiting notable drought tolerance. High heritability and strong inter-trait correlations underscore the breeding potential of these genotypes for developing drought-resistant tomato cultivars.