Beans A high frequency of spontaneous mutations that exceeds other plant species was described in common bean, Phaseolus vulgaris L. (Rukmanski 2005). It was observed that most morphological characters could be mutated in common bean after applying gamma rays or chemical mutagens. In 1979, a breeding programme with the application of induced mutagenesis in French bean started at the Vegetable Crops Research Institute (Maritsa VCRI) in Plovdiv. Zarya is a cultivar suitable for canning industry and is susceptible to common bacterial blight (CBB) (Xanthomonas axanopodis pv. phaseoli). Consequently, for the first time a mutation breeding project in common bean was initiated using gamma irradiation of dry seeds. The lethal dose (LD100) of this cultivar was found to be 160 Gy and the semi-lethal one (LD50) - 120 Gy, therefore, doses of 80 and 100 Gy were used in the mutagenesis breeding programme (Zagorcheva et al., 1983a). Several mutants were selected and showed resistance to CBB (Fig. 5; Table 1).