Evaluation Tolerant of Four Melon Genotypes in Early Growth Stage under Normal and Drought Stress Conditions

Plant breeding initiative in semi-arid and arid area are primarily focused on developing genotypes at early growth stage under normal conditions and keeping them steady during drought stress conditions. Therefore, four melon genotypes responses to drought stress were evaluated in this study during early growth stage. Two treatments for irrigation rates (Full Irrigation= 100%) and (Deficit Irrigation= 50%) were carried out in randomized complete block design (RCBD) with three biological replications in vermiculite culture in greenhouse in the research farm of faculty of agriculture at Sohag university in Egypt during season 2023. Young plants (45 days old plants) were utilized, and phenotypic traits 1º Leaf Score Tolerance, 2º Leaf Score Tolerance, Flowers Numbers, Vine Length, Green Leaves and Brown Leaves Numbers per vine were calculated by comparing differences in drought stress compared to control to identify tolerant and susceptible genotypes. The findings demonstrated that, in all estimated traits under drought stress conditions, there was significant variation between the studied four melon genotypes. whereas, the best results for all the studied traits were produced under normal conditions. Additionally, the highest significant positive correlation was found between 1º Leaf Score Tolerance and 2º Leaf Score Tolerance (0.966*) under normal conditions, and between Vine Length and Green Leaves Numbers per vine (0.999**) under drought stress conditions. Furthermore, the highest significant negative correlation was observed between 2º Leaf Score Tolerance and Flowers Numbers (-0.974*) and Flowers Numbers and Green Leaves Numbers per vine (-0.960*) under normal conditions, and between Vine Length and Brown Leaves Numbers per vine (-0.974*) and Green Leaves Numbers per vine and Brown Leaves Numbers per vine (-0.981*) under drought stress conditions. Besides, Euclidean heatmap clustering analysis grouped studied genotypes according to their response to normal and drought stress conditions, indicating that, the studied melon genotypes offer high potential for particular breeding purposes. These results have produced helpful framework for breeding strategies in the future under drought stress conditions. Conversely, detailed studies are crucial to predict drought stress tolerance performance in novel breeding strategies.