Phenotypic characterization of tomato germplasm in terms of agronomic, physiological and biochemical characteristics under drought conditions

Drought, as one of the abiotic stress factors, is projected to significantly limit tomato cultivation both globally and in our country. Therefore, the development of new varieties that can tolerate drought conditions is of great importance. In this thesis project, a total of 182 tomato genotypes were used as plant material, including local landraces collected from different provinces of Turkey, genotypes obtained from gene banks, commercial cultivars, and foreign tomato genotypes introduced from abroad. Some of these genotypes had been previously characterized in terms of their drought responses in earlier studies. Under drought and control conditions, phenotypic characterization was conducted for two consecutive years in a greenhouse at the Mersin Alata Horticultural Research Institute, focusing on key morphological, physiological, biochemical, and agronomic traits important for tomato. Based on the two-year phenotypic data, a Weighted Scoring Analysis was performed, classifying 63 genotypes as drought-tolerant, 61 as moderately tolerant, and 62 as drought-sensitive. Traits such as stomatal conductance, water use efficiency, fruit yield, fruit weight, diameter, and length were found to have high heritability and to be largely under genetic control. Furthermore, statistical analyses revealed that drought stress had significant effects on plant height, plant weight, fruit yield, leaf chlorophyll content, proline, total soluble sugars, phenolic compounds, and malondialdehyde (MDA) levels. Some genotypes demonstrated significantly improved performance in these parameters under drought conditions, indicating strong stress adaptation capabilities. Based on the results obtained, the most drought-tolerant genotypes will be selected, and breeding programs will be developed in subsequent studies to facilitate the development of new cultivars. Keywords: Solanum lycopersicum., drought stress, tolerance, stress physiology