Upgma analysis, principal component analysis, genetic diversity analysis an
d genetic distance analysis of RAPD data were used to assess the extent of
host specialization in 50 isolates of S. homoeocarpa from five turfgrass ho
sts. In upgma analysis and principal component analysis, the occurrence of
host specialization was not readily apparent based on visual inspection. Ge
netic diversity analysis showed significant differentiation among isolates
from different host species (G(ST) = 0.34, P < 0.001). The strongest eviden
ce for some degree of host specialization came from the statistical analysi
s of genetic distances among isolates. By grouping pairwise genetic distanc
es between isolates based on their host species, and analysing for average
distance within the same host species and among different host species, it
was found that the average distance within species was less than among spec
ies (P < 0.0001). An analysis of molecular variance of the genetic distance
s among isolates found that 32.3% of the total variation was attributable t
o host species. It is concluded that these isolates of S. homoeocarpa showe
d a weak level of host specialization, which was not readily apparent by up
gma or principal component analyses, but was revealed by genetic diversity
analysis and statistical analysis of genetic distances among isolates. Inoc
ulation tests on different host species and tests using a greater number of
isolates are required to confirm the extent of specialization.