Abstract :
A collection of 24 isolates of Verticillium dahliae and 10
isolates of Verticillium longisporum originating from
nine different host plants and from several geographic
regions was tested for host specificity on 11 economically
important crops such as potato, tomato, strawberry,
linseed, three legumes and four Brassica species. In
order to reveal host specificity the potential of each
isolate to induce disease and affect plant yield was
recorded for all isolate–host combinations. The collected
data were statistically processed by means of a
cluster analysis. As a result, the host range of individual
isolates was found to be more dependent on the
vegetative compatibility group (VCG) of the isolate
than on its original host plant provenance. Twenty-two
out of 24 V. dahliae isolates belonged to either VCG 2B
or 4B. VCG 2B isolates showed specificity for legumes,
strawberry, potato and linseed, whereas VCG 4B was
specifically virulent on potato, strawberry and linseed.
Subgroups within VCG 2B and 4B almost lacking any
host preference were designated 2B* and 4B*. Three
isolates from VCG 2B*, however, severely attacked
tomato which is a host outside the authentic host range
of VCG 2B. The pathogenicity of V. longisporum
isolates was restricted to cruciferous hosts. Conversely,
cruciferous plants were not affected by isolates from
VCGs 2B and 4B of V. dahliae. This lack of crossinfectivity
of certain subpopulations of V. dahliae and of
V. longisporum may be useful in the management of this
soil-borne wilt disease.
