Studying the virulence of three bacterial isolates of Xanthomonas campestris i.e., Xm4, Xm6 and Xm8 isolated from different parts of cankered mango trees, in addition to, three isolates of Xanthomonas campestris i.e., X.c. pv. vesicatoria isolate (Xv1) isolated from tomato plants, X.c. pv. campestris isolate (Xc2) isolated from cabbage plants and X.c. pv. citri isolate (Xc3) isolated from citrus fruits on some vegetable hosts revealed that no one of the six tested X. campestris isolates was able to exhibit any one of their pathogenic effects on the different tested vegetable seedlings at 3 days post inoculation by injection or spraying. On the other hand, the three isolates of Xanthomonas campestris i.e., Xm4, Xm6 and Xm8 were able to infect all tested vegetable cultivars with various extents. Also, Xc2 (cabbage isolate) was the highly effective isolate among the six tested isolates in infecting cabbage seedlings either with injection or spraying methods at 10 days post inoculation while, Xv1 isolate was the highest effective one among the six tested isolates in infecting tomato cv. super strain b seedlings. Studying the virulence of the six aforementioned bacteria on some different fruit hosts revealed that three X. campestris isolates (Xm4, Xm6 and Xm8) were the highly pathogenic isolates of mango (cv. Ewasy), peach cv. Florida and pear cv. Lecont transplants among the six tested isolates when inoculated by injection or spraying followed by Xc2, Xc3 and Xv1, respectively. Also, transplants of plum cv. Hollywood and apple cv. Ana were not able to infect with any one of the tested Xanthomonas isolates. On the other hand, X. campestris p.v citri (Xc3) was the only isolate among the six tested isolates had the ability to infect orange and lemon transplants with highly pathogenic reaction. As for the DNA-polymorphism among the six tested X. campestris isolates using RAPD-PCR technique with five primers i.e., D3, RI, A1R, D02 and E07, data exhibited that the five tested RAPD primers were good in revealing the DNA-polymorphism among the six tested Xanthomonas campestris isolates i.e., Xm4, Xm6, Xm8, Xv1, Xc2 and Xc3 where most of them exhibited RAPD-PCR amplicons with molecular weights recorded with the six tested bacterial isolates to confirm the high similarity among them. Also, the RAPD primer RI was the best one among the five tested primers in revealing RAPD-PCR amplicons with molecular weights confirmed the entirely similarity and relatively within the three tested mango bacterial isolates i.e., Xm4, Xm,6 and Xm8 and confirmed also the similarity of them with the three other tested bacterial isolates.
Keywords: RAPD-PCR, DNA-Polymorphism , Xanthomonas campertris mango, canker