Twenty-six isolates representing six morphologically similar taxa
of Tilletia occurring in the western U.S.A. were compared using
randomly amplified polymorphic DNA (RAPD) markers and restriction fragment
length polymorphisms (RFLP) of the 5·8 s rDNA
and flanking ITS regions. Two distinct clusters were separated in the
dendrogram based on the RAPD analysis. One cluster
contained isolates of T. controversa, Apera
interrupta-infecting isolates of a potentially new species of
Tilletia, and isolates of the
Bromus-infecting varieties bromi-tectorum and guyotiana
of the
T. fusca (=T. bromi) complex. The second cluster contained
Vulpia-infecting isolates of T. fusca var. fusca.
The
separation of the Bromus-infecting varieties from the
Vulpia-infecting variety of T. fusca
was supported by distinct restriction digest phenotypes. The RAPD analysis
was
more sensitive than the RFLP analysis, and allowed
separation of the Bromus-infecting varieties bromi-tectorum
and
guyotiana corresponding to host specificity shown in previous
studies.
The presence of genetically distinct populations of T. fusca var.
fusca occurring on V. microstachys and V. octoflora
is
indicated by RAPD and RFLP analyses. Species status of T. togwatii,
a
bunt infecting Poa reflexa that was previously removed from the
T. fusca complex, is also supported by RAPD and RFLP analyses.