Fusarium subglutinans has been associated with many hosts.
Some isolates of the fungus are responsible for pitch canker disease of
pines. A South African population of F. subglutinans from pine
seedlings
was characterized by comparing it to isolates from various
hosts, pine and non-pine. A total of 26 isolates representing six different
hosts
were selected for the study. Cultural and
morphological characteristics were studied. Virulence of isolates was tested
on
1-yr-old Pinus patula seedlings. Sexual compatibility of
isolates of F. subglutinans with B- and E-tester strains, and
crossings
of pine isolates in all possible combinations, were performed.
Pine isolates were also compared with pitch canker and non-pine isolates
using
random amplified polymorphic DNAs (RAPDs).
All isolates were morphologically characteristic of F. subglutinans,
but differed somewhat in cultural features. Only isolates from pine
were pathogenic to P. patula seedlings. Virtually no isolates
were
sexually compatible with the fertile tester strains. An exception
was isolate MRC 115 from maize. Some pine isolates (MRC 6211 and MRC 6217)
were,
however, sexually compatible with South
African (MRC 6213) and pitch canker (MRC 6229) isolates. Cluster patterns
constructed from RAPD profiles revealed that isolates
clustered according to host. South African isolates from pine were related
to
the pitch canker isolates from other areas, and were
similar to non-pine isolates only in morphology. Virulence, genetic analyses
and composite RAPD data suggest that pine isolates
originate from the same gene pool, and probably represent a distinct new
biological species.