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dc.contributor.authorAmaradasa, Bimal Sajeewaen_US
dc.date.accessioned2014-03-14T21:17:46Z
dc.date.available2014-03-14T21:17:46Z
dc.date.issued2011-07-19en_US
dc.identifier.otheretd-08142011-170650en_US
dc.identifier.urihttp://hdl.handle.net/10919/39174
dc.description.abstractRhizoctonia blight (sensu lato) is a common and serious disease of many turfgrass species. The most widespread causal agent R. solani consists of several genetically different anastomosis groups (AGs) and subgroups. Though anastomosis or hyphal fusion reactions have been used to group Rhizoctonia species, they are time consuming and sometimes difficult to interpret. Anastomosis reactions are incapable of identifying isolates belonging to different AG subgroups within an AG. This study evaluated molecular techniques in comparison with traditional anastomosis grouping (AG) to identify and group isolates of Rhizoctonia. More than 400 Rhizoctonia isolates were collected from diseased turfgrass leaves from eight geographic areas in Virginia and Maryland. A random sample of 86 isolates was selected and initially characterized by colony morphology, nuclei staining and anastomosis grouping. Molecular identification was performed by analysis of rDNA-ITS region and DNA fingerprinting techniques universally primed PCR (UP-PCR) and amplified fragment length polymorphism (AFLP). The cladistic analysis of ITS sequences and UP-PCR fragments supported seven clusters. Isolates of R. solani AG 1-IB (n=18), AG 2-2IIIB (n=30) and AG 5 (n=1) clustered separately. Waitea circinata var. zeae (n=11), and var. circinata (n=4) grouped separately. A cluster of six isolates (UWC) did not fall into any known Waitea group. Most of the binucleate Rhizoctonia-like fungi (BNR) (n=16) grouped separately. AFLP grouping also largely agreed with the above results. However, UWC isolates clustered into two groups. Molecular analyses corresponded well with traditional anastomosis grouping by clustering isolates within an AG or AG subgroup together. UP-PCR cross-hybridization could distinguish closely related Rhizoctonia isolates to their infraspecies level. Genetically related isolates belonging to the same AG subgroups cross-hybridized strongly, while isolates of different AGs did not cross-hybridize or did so weakly. Sequence-characterized amplified region (SCAR) markers were generated from UP-PCR products to identify isolates of major pathogenic groups AG 1-IB and AG 2-2IIIB. Specific primer pairs successfully distinguished isolates of AG 1-IB and AG 2-2IIIB from isolates of other AGs. Sensitivity of Rhizoctonia species and AGs was tested in vitro to commercial formulations of iprodione, triticonazole and pyraclostrobin. W. circinata isolates were moderately sensitive to iprodione while isolates of R. solani and BNR were extremely sensitive. Isolates of AG 2-2IIIB showed less sensitivity to triticonazole than other Rhizoctonia isolates. W. circinata var. zeae isolates were moderately sensitive to pyraclostrobin while most of the other isolates were extremely sensitive.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartAmaradasa_BS_D_2011.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectEC50en_US
dc.subjectfungicide sensitivityen_US
dc.subjectSCAR markersen_US
dc.subjectcross-hybridizationen_US
dc.subjectAFLPen_US
dc.subjectUP-PCRen_US
dc.subjectrDNA-ITSen_US
dc.subjectanastomosisen_US
dc.subjectWaitea circinataen_US
dc.subjectRhizoctonia solanien_US
dc.subjectbrown patchen_US
dc.titleAccurate identification and grouping of Rhizoctonia isolates infecting turfgrasses in MD and VA and their sensitivity to selected fungicides in vitroen_US
dc.typeDissertationen_US
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen_US
dc.contributor.committeememberSchmale, David G. IIIen_US
dc.contributor.committeememberGoatley, J. Michael Jr.en_US
dc.contributor.committeememberLakshman, Dilipen_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08142011-170650/en_US
dc.contributor.committeecochairHorvath, Brandon J.en_US
dc.contributor.committeecochairBaudoin, Antonius B. A. M.en_US
dc.date.sdate2011-08-14en_US
dc.date.rdate2011-09-08
dc.date.adate2011-09-08en_US


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