Morphological Diversity and Genotypic Discrimination in Tomato (Solanum lycopersicum L.): Implications for Breeding, Stress Tolerance, and Germplasm Conservation

Abstract

Understanding the extent and distribution of phenotypic diversity in tomato (Solanum lycopersicum L.) is fundamental for cultivar identification, genetic improvement, and the sustainable utilization of germplasm resources. This study evaluated 15 key qualitative morphological traits across nine genetically diverse tomato genotypes to characterize their phenotypic variability and assess its implications for breeding, particularly for stress resilience. The field experiment was conducted under irrigation during the 2024–2025 off-season at two distinct agro-ecological locations in western Ethiopia: Bako Tibe (1560 m.a.s.l.) and Gambella Tare (2697 m.a.s.l.). Significant inter-genotypic variation was observed for all qualitative descriptors. Fruit traits exhibited pronounced diversity, including predominant shapes (ranging from pyriform to cylindrical), shoulder morphology (flat to strongly depressed), cross-sectional outlines (angular, rounded, irregular), and pistil scar patterns (dot, stellate, linear). Notably, 66.66% of genotypes demonstrated high fruit size homogeneity, while angular cross-sections were predominant (55.55%). The prevalence of abiotic stress-related disorders was genotype-dependent: blotchy ripening was observed in 55.55% of genotypes (slight symptoms), sunscald in 44.44% (exposed), and radial cracking in 55.55% (slightly affected), underscoring the interaction between genetic predisposition and environmental factors. Leaf morphological traits, including type (potato, dwarf, Peruvianum) and attitude (drooping, semi-erect, horizontal), further corroborated the substantial genetic diversity. Correlation analysis from the accompanying quantitative trait evaluation revealed that average fruit weight had a strong, positive, and significant genotypic correlation with total marketable fruit yield (rg = 0.35) and fruit yield (rg = 0.716). Our findings align with global studies on tomato landrace diversity and demonstrate that systematic morphological characterization remains a powerful, cost-effective first step for germplasm conservation and for selecting parental lines with desirable agronomic traits, including stress tolerance. The identified genotypes, particularly; 'Cochoro' for yield and 'Melka-salsa' for fruit quality, offer immediate value for breeding programs targeting climate-resilient and market-preferred cultivars.