-Diversity in aggressiveness and ISSR-Polymorphism of Uromyces appendiculatus single uredinium isolates obtained from common bean cultivation areas in Egypt.-

To study the diversity in the strains of bean rust pathogen in Egypt, 12 single uredinium isolates (SUIs), were obtained from bean fields representing most of the known bean-growing areas in Egypt. Variations in SUIs aggressiveness were assessed based on three quantitative components: Incubation period (IP), Infection frequency (IF) and Pustule size (PS).There were significant differences among SUIs in regard to the incubation period. incubation period ranged from 7.3 to 9.9 days. In regard to the Infection frequency, the number of pustules/cm2 produced by the tested SUIs significantly differed. The number of pustules/cm2 ranged between 1.6-4.6 pustules/cm2. In regard to the Pustule size, the tested SUIs significantly differed in the size of the produced pustules. The largest pustule sizes were > 4 mm while the smallest sizes of pustules were < 2.5 mm.Polymorphism among SUIs were tested using 11 ISSR primers. High level of diversity among SUIs based on ISSR molecular markers were detected. The generated bands ranged between 160 and 600 bp. The similarity between SUIs ranged from 0.80 to 0.98.