Assessment of Genetic Diversity in Summer Squash Genotypes Using some Yield Traits and DNA Markers Analysis under Sinai Conditions

Fourteen summer squash genotypes were used to assess their genetic diversity and relationships using some yield traits (Fruit length, fruit diameter, fruit shape index, average fruit weight, No of fruits/plant, fruit yield, and total soluble solids %) and DNA markers (Random Amplified Polymorphic DNA, inter-simple sequence repeat, Start Codon Targeted polymorphism) analyses. Two open field trials were executed at two locations, i.e., El-Arish (L₁) and Ras Sidr (L₂) in the North and South Sinai-Egypt, respectively. Significant differences were observed between both locations and indicated the superiority of (L₁) than (L₂) in all studied traits, while the interaction between genotype and location was significant for all studied traits. The location had a major effect on the relative genotypic potential of these traits, in which the genotype × location interaction was highly significant. SQ6genotype ranked as the first in the fruit yield/plant and SQ2 for fruit diameter followed by SQ7and SQ2 for fruit shape as well as SQ13and SQ12for the number of fruits/plant in L₁ and L₂ locations, respectively. Additionally, high polymorphism percentage (P %) was detected using RAPD (85%), ISSR (79.25%) and SCoT (69.44). Among the 15 studied primers, OP-B17 showed the maximum P% (100%) followed by primer OP-C17 (90.9 %) which also scored the highest values for polymorphism information content, effective multiplex ratio, and marker index. In addition, OP-K01 represented the maximum value of resolving power (12.56), indicated that these primers were highly informative. Intriguingly, 55 positive and two unique negative bands were amplified, out of which (33) bands were generated by RAPD followed by SCoT (15) and ISSR (9). In this regard, OP-C17 and SQ1 genotype produced the highest number of unique marker18 and 11amplicon, respectively. Moreover, the maximum similarity was found between SQ 11 and SQ 12 indicating that both genotypes were the most similar. Cluster and PCA analysis using RAPD, ISSR, and SCoT data grouped the 14 squash genotypes into four, three and two distinct clusters, respectively. Generally, the yield traits alongside molecular results showed significant information that may be utilized to sort and relationship between the studied summer squash genotypes under different conditions