Jt. Blodgett et Gr. Stanosz, Differences in aggressiveness of Sphaeropsis sapinea RAPD marker group isolates on several conifers, PLANT DIS, 83(9), 1999, pp. 853-856
Seedlings of Scot's pine varieties East Anglia and Austrian Hills, red pine
, mugho pine variety Pumileo, Colorado blue spruce, Douglas-fir, and balsam
fit were wounded and inoculated with water agar plugs colonized by isolate
s of the two random amplified polymorphic DNA (RAPD) marker groups (A and B
) of Sphaeropsis sapinea. Isolates were obtained from hosts in Michigan, Mi
nnesota, and Wisconsin. Symptom severity (distance from the inoculation sit
e at which necrotic needles were present) resulting from inoculations with
each group A isolate exceeded that from inoculations with each group B isol
ate on all hosts except Colorado blue spruce. Hosts varied considerably in
their responses to group A isolates. Based on symptom severity, East Anglia
Scot's pine was most susceptible and balsam fir was least susceptible when
inoculated with group A isolates. The pathogen was recovered from both sym
ptomatic and asymptomatic seedlings inoculated with isolates of either grou
p. Results emphasize the importance of characterizing a RAPD marker group(s
) of S. sapinea encountered in the field or used in research; the need for
comparative evaluations of resistance among coniferous genera, species, and
varieties to S. sapinea of both groups; and the potential for asymptomatic
persistence of S. sapinea from both groups in or on several coniferous hos
ts.