Abstract

Summer squash is an important member of the family Cucurbitaceae. It is one of the most popular vegetable crops cultivated in Egypt. Increasing yield and improving fruits quality are the targets for growers. Therefore, this study aimed to evaluate the extent of genetic variations, heritability, as well as expected genetic advance for growth and yield related traits in four genotypes of summer squash subjected to three doses of ultraviolet irradiation. Data were subjected to the analysis of variance for the important components of yield and agronomic traits. The results showed relatively small differences between phenotypic and genotypic variance for the number of leaves per plant, chlorophyll concentrations in leaves, and fruits. Larger magnitude of difference was obtained between phenotypic and genotypic coefficient of variations in the expression of leaf area, female flowers, male flowers developed per plant, and carotenoids concentration in fruits, indicating that environmental factors played predominance role in the expression of these traits. Moderate heritability value was obtained for fruits weight per plant coupled with high genetic advance as a percentage of mean. Therefore, selection based on the phenotypes will improve the mean performance of fruits weight per plant in the selected progenies.

Key words: Summer squash, ultraviolet irradiation, genetic components, genetic advance, heritability.