Evaluation of fusarium oxysporum F. SP. vasinfectum isolates obtained from cotton i̇n terms of vegetative compatibility groups, mycoviral dsRNA content and hypovirulence

Objective: This study was conducted to investigate the vegetative compatibility group (VCG), mycoviral dsRNA presence and hypovirulence of Fusarium oxysporum f.sp. vasinfectum (Fov) isolates, which were collected from cotton fields in Aydın province. Materials and Methods: A total of 100 Fov isolates, selecting from the stock culture collection of Fov in the Phytopathology Laboratory of the Plant Protection Department of the Faculty of Agriculture at Aydın Adnan Menderes University. For being used in VCG tests, Nit mutants of Fov isolates were generated in minimal media (MM) containing 6% KClO₃, and their nit phenotypes were determined on three different selective media containig nitrate, nitrite, hypoxanthine, respectively. Vegetative compatibility was measured by examining the presence/absence of the heterokaryon formation between two growing mutant isolates when they were paired in MM. dsRNA analysis was investigated in 22 selected isolates, and dsRNA profiles were visualized by agarose gel electrophoresis. The hypovirulence potential of dsRNA-positive isolates was tested by virulence assays on the cotton variety Fiona. Results: In the study, 59 of 100 isolates showed chlorate-resistant development; a total of 237 nit mutants were obtained from these isolates. As a result of heterokaryon formation assay, three different VCG groups were detected in the Fov population in Aydın; one group was found in all districts of Aydın, while the other two groups were only found in the Nazilli district. dsRNA analysis of 22 isolates revealed the presence of dsRNA in 6 isolates. In the virulence test, some of the dsRNA positive isolates showed low virulence in cotton seedlings. Conclusion: This study marks that VCG and mycoviral dsRNA content of Fov have been studied fort the first time in Türkiye. Considering that Fov is an asexually reproducing fungus, the identification of three different VCG groups in cotton cultivation areas in Aydın Province indicates the relative presence of significant genetic diversity. Although the presence of isolates with dsRNA profiles in the analyses suggests that microviral infections may be present in Fov isolates, this needs to be confirmed by advanced virus diagnostic studies. The low virulence of dsRNA-carrying isolates also suggests the possibility of microvirus-derived hypovirulence. Future studies examining the relationship between Fov, mycoviruses, and cotton in more comprehensive studies are important for a better understanding of the subject. Furthermore, monitoring VCG diversity in the region should be considered an important tool for understanding the biology of Fov and planning integrated disease control methods.