sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDU Faculty of Forestry Journal
Serial: A, Number: Special Issue, Year: 2009, ISSN: 1302-7085, Page: 255
EXAMINING THE GEOGRAPHIC DISTRIBUTION OF Diplodia pinea
AND D. scrobiculata:
A CASE STUDY FROM MINNESOTA, USA
J. S. ALBERS 1 , Denise R. SMITH 2 , Glen R. STANOSZ 2*
1 Division of Forestry, Minnesota Department of Natural Resources, Grand Rapids, MN, 55744, USA
2 Department of Plant Pathology, University of Wisconsin-Madison, WI, 53706, USA
* grs@plantpath.wisc.edu
Although the shoot blight and canker pathogen Diplodia pinea is more
commonly reported and is distributed in native and exotic pine stands in much of
the world, a second very similar and closely related fungus, D. scrobiculata, has
been detected in the USA, Mexico, France, Israel, Italy, and Spain, and is likely
present in other countries. Both of these fungi are associated with red pine (Pinus
resinosa) and jack pine (P. banksiana) in the northcentral and northeastern USA.
Their distribution in Minnesota was studied by examination of seed cones (on
which these fungi sporulate). 100 cones collected from the forest floor of each of
109 red pine stands and 28 jack pine stands were visually examined for Diplodia
pycnidia and conidia. At least one of these fungi was detected from 106 of 109 red
pine stands and from all jack pine stands. Mean frequencies of positive red and
jack pine cones, respectively, were 27% (range 0-84%) and 12% (range 2-41%).
PCR assays confirmed pathogen identity for subsets of cones. D. pinea was
detected from cones collected at 102 of 109 red pine stands (69% of red pine cones
tested), and 18 of 28 jack pine stands (18% of jack pine cones tested). In contrast,
D. scrobiculata was detected from cones collected at only 26 of 109 red pine
stands (7% of red pine cones tested), but 26 of 28 jack pine stands (79% of jack
pine cones tested). These fungi sometimes co-occurred in stands of either host, and
occasionally both were detected from individual cones of either host. Although
differences between D. pinea and D. scrobiculata in host association, presence at a
given location, and frequency of occurrence at a given location were apparent, each
was found across the entire area surveyed.
255