Selection of Melon Genotypes Tolerant to Biotic and Abiotic Stresses Via Selection Indices

Aims: Select melon genotypes with ideal traits and compare two selection indices. Study Design: 26 melon genotypes were evaluated using a randomized complete block design with three replications. Place and Duration of Study: In August 2023, the melon genotypes were transplanted inside greenhouse, located in Saltillo, Coahuila. Methodology: The inoculation with the fungus causing powdery mildew began in 15-day-old seedlings. Disease severity was visually assessed 28 days after transplant using a scale from 0 to 4, where 0 indicates high resistance and 4 indicates high susceptibility. In addition, the area under the disease progress curve was calculated. At 51 days after transplant, during flowering, the crop was subjected to severe heat stress for three days, and the variables relative chlorophyll content and leaf temperature were measured. When the fruit reached maturity, the following parameters were evaluated: days to first cut, fruit weight, total soluble solids, flavor, skin thickness, and pulp thickness. Results: The selection index highlighted genotypes 18, 27, 15, 20, 3, 12, 17, 29, and 13 as superior, while the MGIDI index selected genotypes 18, 27, 20, 12, 23, 29, 10, 5, and 15. The Harper-type melons (18, 27, and 15) stood out in both indices due to their combination of high yield, fruit quality, powdery mildew tolerance, chlorophyll content, and lower temperature under heat stress. Conclusion: The Harper-type melons were identified as the most promising. The discrepancy between the genotypes selected by the indices may be due to various factors related to the calculation methodology.