Vegetative compatibility of Fusarium oxysporum f. sp. dianthi from carnation in Israel.

Auxotrophic mutants were used to determine vegetative relatedness among isolates of Fusarium oxysporum f.sp. dianthi (F.o.d.), the vascular wilt pathogen of carnation. At the first stage, different nitrate-non-utilizing (nit) mutants were produced from 11 isolates of F.o.d. collected in Israel. Complementation (heterokaryon) tests showed that all the isolates belonged to a single vegetative compatibility group (VCG), and two mutants were chosen as its testers. Additional isolates of Fusarium from carnation, collected during 1986-88, were analysed for pathogenicity and vegetative compatibility with the testers. A total of 170 Fusarium isolates, obtained from 42 cultivars at 40 sites, were tested. All the nit mutants of all the 132 pathogenic isolates formed heterokaryons with the testers, indicating that they belonged to the same VCG. None of the 38 non-pathogenic isolates was vegetatively compatible with the testers. The nit mutants retained pathogenicity to carnation. The F.o.d. testers were not compatible with testers of five other formae speciales of F. oxysporum. Thus, F.o.d. appears to constitute a distinct genetic population within the F. oxysporum complex.