Genetic Diversity And Vegetative Compatibility Among Verticillium Dahliae Strains

The genus of Verticillium dahliae is the most important fungal pathogen which causes Verticillium wilt in cotton (Gossypium hirsutum L.) worldwide. A collection of 44 isolates of V. dahliae was isolated from cotton in China and four isolates were obtained from Egypt. The vegetative compatibility and genetic diversity of those isolates were determined by nitrate-nonutilizing (nit) mutant and Inter Simple Sequence repeat (ISSR) techniques respectively. The results indicated that 566 mutants were obtained, among them, 453 mutants were characterized as Nit1 mutant, occupied 80.03% and 107 characterized as NitM mutant, occupied 18.90%, while 10 characterized as Nit3 mutant, occupied 1.76%.On behalf of vegetative compatibility testing showed that 48 isolates of V. dahliae were successfully assigned to two vegetative compatibility groups (VCGs), among them, thirty six isolates were compatible with Egyptian isolates and classified as VCG1 with defoliating Pathotype, while the 12 remaining isolates were classified as VCG2 with non-defoliating Pathotype. The results further confirmed that the presence of the defoliating pathotype (VCG1) of V. dahliae in the mainland of China. Testers from Egypt formed heterokaryons with VCG testers from the main groups and it was emphasized that careful selection of isolate testers was an essential step to get a clear picture of VCG diversity.The amounts of genetic variation were evaluated by ISSR technique by using fifteen primers. All of them showed the diversity among isolates. The result of analysis indicated that the dendrogram was classified those isolates into two main clusters at 74% similarity and PIC Means Polymorphism Information Content for ISSR marker systems was found to be useful for the genetic diversity studies in V. dahliae and identified the variation within isolates of cotton. A total of 238 polymorphic amplicons were observed in ISSR markers with average of 0.93 of PIC, and the lowest and the highest PIC values were 0.861 (P25) and 0.971 (P4) respectively. There were 2424 fragments obtained by amplification of ISSR with fifteen primers and scored as discrete character data (presence l / absence 0), and the total number of polymorphic bands were 238 with an average of 0.93. It indicated that ISSR molecular analysis had comparatively high polymorphism in V.dahliae of cotton and the polymorphic rate reached at 83.00%. The genetic similarity matrix was obtained among all the used isolates in the study. For the ISSR marker, the average similarity value was 0.76 which used as a cutoff value for defining the clusters. The highest similarity was 0.97. However, the lowest similarity was 0.56. The results indicated that genetic diversity was existed among V. dahliae isolates within vegetative compatibility groups (VCGs) by using molecular marker assays (ISSR).In conclusion, the diversity of V. dahliae isolated from China and Egypt can prove to be a highly significant of morphological and genetic...