Mutagenic effect of ultraviolet rays on sex expression in summer squash genotypes

Abstract

The present study aimed to induce genetic variations within the control of sex expression in summer squash using ultraviolet rays (UV) as a physical source of mutations in plants. Because the sex expression in summer squash is fundamentally controlled mainly by genetics and partially by the environment. Therefore, this study tries to increase floral differentiation of female flowers, as well as decrease male flowers developed per plant, because summer squash usually exhibit more male flowers and lower female flowers. This will cause decreases in fruits yield per plant. This study was designed in a randomized complete block design with a factorial investigation. It was included four genotypes of summer squash subjected to four exposure periods of UV rays, with three repetitions for each experimental unit. The results showed that genotype number four increased the features of female flowers by 28% and 14% at 4 and 8 minutes of exposure period, respectively. The 12 – minute exposure period significantly increased floral differentiation among all genotypes toward male flowers developed per plant. Meanwhile, genotype number two enhanced floral differentiation toward female flowers by 14% at 8 minutes of exposure period, indicating that these few periods of exposure to UV irradiation may be responsible for induced benefit mutations in cucurbits affected on sex expression, as it induced high number of female flowers. The results indicated that UV irradiation had a direct role in promoting floral differentiation as it inducement higher female flowers in some genotypes leading to improve floral characteristics, as a consequence increased fruits yield per plant.