Vegetative compatibility of Verticillium dahliae isolates from potato and sunflower using nitrate non-utilizing (nit) mutants and PCR-based approaches

Abstract

Vegetative compatibility groups (VCGs) of 12 potato and nine sunflower isolates of Verticillium dahliae were determined using both nitrate non-utilizing (nit) mutants and multiplex-nested-PCR approaches. Based on analysis of nit mutants, most potato isolates showed strong compatibility with VCG 4A and weak compatibility with VCG 4B; one potato isolate was also weakly compatible with VCGs 2A, 2B and 3. Sunflower isolates were more variable and most of them showed weak reactions with VCG 4A and 4B. One sunflower isolate, Vs06-14, was compatible only with VCG3 testers, whereas another isolate, Vs06-20, was compatible with all VCG groups except VCG2A. Vegetative compatibility of four selected isolates, two from potato and two from sunflower, was also investigated after passing them through potato or sunflower for four generations. The VCG of one potato isolate did not change, whereas the other one changed from VCG4B to 4A. One sunflower isolate, initially compatible with both VCG4A and 4B, became incompatible with both. The other sunflower isolate was not compatible with any VCG and remained so. In a second part of this work, multiplex-nested-PCR was carried out to characterize VCGs of the same isolates of V. dahliae. Vegetative compatibility grouping using this approach assigned the V. dahliae isolates to VCG1, 2A, 3 or 4A. Six of the 12 potato isolates and four of the nine sunflower isolates of V. dahliae could not be identified or placed in any VCG group based on PCR results. In the present study, the multiplex-nested-PCR results were confirmed using nit mutants. As such, PCR-based methods will require more specific primers before they can replace the approach based on nit mutants. Current address of A.F. El-Bebany: Department of Plant Pathology, Faculty of Agriculture, Alexandria University, El-Shatby, 21545, Alexandria, Egypt.