Molecular and Morphological Variations Induced by Gamma Rays in Yardlong Bean

Yardlong bean (Vigna unguiculata (L.) Walp. sub. sp. sesquipedalis) is a climber annual Vigna crop of Leguminosae family with chromosome number 2n = 2x = 22. It’s known as long-podded cowpea, asparagus bean, pea bean, snake bean, garter bean and Chinese long bean. It has ability to fix atmospheric nitrogen with its symbiotic bacteria (Rhizobia) and increases productivity of the soil (Pandey et al., 1989). It is much more a climbing and trailing plant than the cowpea, often reaching 9-12 feet in height and it is characterized by its very long pods 30-90 cm in length with seeds usually 8–12 mm long. It is commonly cultivated T study was carried out to identify the genetic variations in yardlong bean plants irradiated by various doses (75, 150, 300, 450 and 600Gy) of gamma rays using RAPD and ISSR markers techniques as well as, their effect on some vegetative traits were studied. ten RAPD and 10 ISSR markers were used in this investigation. The obtained results showed that the ten RAPD primers produced 117 bands only 94 of them were polymorphic while 23 bands were monomorphic. The percentages of polymorphism among primers ranged from 0.0% to 100%. All of the RAPD primers produced unique bands except OPK-06 primer which did not produced any unique bands. Meanwhile, 62 amplified bands including 26 polymorphic and 36 monomorphic bands were generated by ten ISSR primers. All of the ISSR primers did not produce any unique bands except ISSR4 primer which produced only one unique band, these results demonstrated that this unique sequence could be used as a molecular marker associated with gamma irradiation. The field results showed that the emergence percentage decreased with increasing doses up to 600Gy treatment which gave the lowest emergence percentage. Inconstant values of vegetative characteristics were obtained after each treatment with gamma ray doses; 300Gy treatment gave the highest value of plant height, number of branches, pod length and number of seeds per pod compared to control and other treatments. The values of coefficients of phenotypic and genotypic variation, heritability and expect genetic advance did not follow regular increase or decrease with the radiation doses in both seasons. The present data demonstrate that using gamma rays to induce DNA polymorphism in this plant genome which might be lead to appearance of a desired phenotype and genetic characteristics which could be used in yardlong bean improvement programs.