Accurate identification and grouping of Rhizoctonia isolates infecting turfgrasses in MD and VA and their sensitivity to selected fungicides in vitro

Simple item page
dc.contributor.authorAmaradasa, Bimal Sajeewaen
dc.contributor.committeecochairHorvath, Brandon J.en
dc.contributor.committeecochairBaudoin, Antonius B.en
dc.contributor.committeememberSchmale, David G. IIIen
dc.contributor.committeememberGoatley, J. Michael Jr.en
dc.contributor.committeememberLakshman, Dilipen
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen
dc.date.accessioned2014-03-14T21:17:46Zen
dc.date.adate2011-09-08en
dc.date.available2014-03-14T21:17:46Zen
dc.date.issued2011-07-19en
dc.date.rdate2011-09-08en
dc.date.sdate2011-08-14en
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
dc.description.degreePh. D.en
dc.identifier.otheretd-08142011-170650en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08142011-170650/en
dc.identifier.urihttp://hdl.handle.net/10919/39174en
dc.publisherVirginia Techen
dc.relation.haspartAmaradasa_BS_D_2011.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectEC50en
dc.subjectfungicide sensitivityen
dc.subjectSCAR markersen
dc.subjectcross-hybridizationen
dc.subjectAFLPen
dc.subjectUP-PCRen
dc.subjectrDNA-ITSen
dc.subjectanastomosisen
dc.subjectWaitea circinataen
dc.subjectRhizoctonia solanien
dc.subjectbrown patchen
dc.titleAccurate identification and grouping of Rhizoctonia isolates infecting turfgrasses in MD and VA and their sensitivity to selected fungicides in vitroen
dc.typeDissertationen
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Amaradasa_BS_D_2011.pdf
Size:
1.37 MB
Format:
Adobe Portable Document Format
Download

Collections

Doctoral Dissertations