Spread of White Hypovirulent Strains of Cryphonectria Parasitica Among American Chestnut Trees at the Lesesne State Forest

Simple item page
dc.contributor.authorRobbins, Nancyen
dc.contributor.committeechairGriffin, Gary J.en
dc.contributor.committeememberSantopietro, Gracielaen
dc.contributor.committeememberElkins, John Rushen
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen
dc.date.accessioned2014-03-14T20:48:09Zen
dc.date.adate1998-02-17en
dc.date.available2014-03-14T20:48:09Zen
dc.date.issued1997-12-19en
dc.date.rdate1999-02-17en
dc.date.sdate1997-12-19en
dc.description.abstractSixty-two natural cankers on branches and main stems of three 16-year-old grafted American chestnut trees at the Lesesne State Forest were sampled for Cryphonectria parasitica. Cankers were sampled in 1996 and 1997 at various distances from the main stem zone on the grafts (ground to 183 cm) that was inoculated in 1982 and 1983 with a mixture of dsRNA-containing white and pigmented hypovirulent strains. Grafted trees exhibited a high level of blight control, and all bark cores extracted from cankers on the grafted trees showed superficial necrosis. Bark cores extracted from these cankers yielded 156 isolates of C. parasitica. Fifty-three of these isolates were white, and 103 were pigmented. The farthest canker containing a white isolate was located 564 cm from the zone inoculated with hypovirulent strains (H-inoculated zone). The number of white isolates recovered per canker on the grafted trees near the H-inoculated zone (< 0.5 maximum sampling distance) was significantly greater (P=0.0039) than the number of white isolates recovered per canker on the grafted trees far from the H-inoculated zone (>0.5 maximum sampling distance). Lloyd's index of patchiness value for the frequency of white isolates in cankers was 1.36, indicating that white isolates were slightly aggregated in cankers. White isolates of C. parasitica were found in two of seven artificially established cankers 5 months after inoculation with a pigmented virulent strain (WK). Thirteen of 14 pigmented isolates collected from these cankers after 5 months were compatible with WK in vegetative compatibility (VC) tests. Eight of 25 white isolates recovered 5, 11, and 50 months after WK inoculation converted the pigmented WK strain to the white hypovirulent phenotype in vitro. Sixty-five pigmented isolates collected from natural cankers were paired in VC assays, revealing 28 VC groups. All 11 white isolates of C. parasitica assayed contained a 12.7 kb dsRNA in high concentrations. None of 48 pigmented isolates assayed contained dsRNA. All white isolates tested in virulence trials on American chestnut stems in a forest clearcut were hypovirulent, based on low canker severity indices. Little or no dissemination of white strains to cankers on the American chestnut stump sprout clusters, which surround the grafted trees, was found. In the future, to maximize spread of white hypovirulent strains on American chestnut trees, it may be beneficial to re-inoculate trees with hypovirulent strains farther up the main stem after substantial tree growth has occurred.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-11198-123114en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-11198-123114/en
dc.identifier.urihttp://hdl.handle.net/10919/35763en
dc.publisherVirginia Techen
dc.relation.haspartrevision.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectchestnut blighten
dc.subjecthypovirulenceen
dc.subjectCryphonectria parasiticaen
dc.subjectascomyceteen
dc.titleSpread of White Hypovirulent Strains of Cryphonectria Parasitica Among American Chestnut Trees at the Lesesne State Foresten
dc.typeThesisen
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
revision.pdf
Size:
655.3 KB
Format:
Adobe Portable Document Format
Download
Collections
Masters Theses