Résumé
25 isolates of Verticillium dahliae obtained from olive trees: 18 of them originating from two regions of Algeria (Nord-ouest and Kabylie), 4 isolates from France and 3 from Syria. They were investigated using complementation tests with nitrate-nonutilizing (Nit) mutants to know their vegetative compatibility. Among 250 chlorate-resistant sectors obtained, only 187 were Nit mutants. Three types of Nit mutants were obtained (Nit1, Nit3 and NitM) on the basis of the fungal phenotype. Nit1 mutants were the most frequent (71.6%), followed by NitM (16.6%) and Nit3 (11.8%). Based on their ability to form heterokaryons, all olive pathogenic isolates were grouped into a single vegetative compatibility groups (VCG). This is a good indication of the homogeneity of the Algerian V. dahliae population. The results also suggest the absence of a relationship between geographical origin of strains and VCG.