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Characterisation of Rhizoctonia solani isolates from potatoe in Western Australia using Anastomosis groupings, Pectic Isozyme Groupings, Polymorphism of the ITS Region of the rRNA

Burges, Nichole (2002) Characterisation of Rhizoctonia solani isolates from potatoe in Western Australia using Anastomosis groupings, Pectic Isozyme Groupings, Polymorphism of the ITS Region of the rRNA. Honours thesis, Murdoch University.

Abstract

The basidiomycete fungus, Rhizoctonia solani is a complex soilborne plant pathogen. As a species R. solani is comprised of many strains, which differ in host specificity as well as physiological characteristics such as colony morphology. R. solani is a major pathogen of the cultivated potato, Solanum tuberosum, and causes a number of economically important diseases worldwide.

The aim of this study was to characterise R. solani isolates associated with diseases of potatoes in Western Australia. A hierarchical and more general survey of the major potato growing regions across the state were conducted, and isolates collected were characterised using anastomosis groups, pectic zymograms and polymorphism analysis of the internal transcribed spacer region of the rDNA.

Symptomatic and non-symptomatic potato plants were sampled from Myalup, Baldivis, Manjimup, Nannup, the Porongurups and Esperance. A total of 140 isolates of Rhizoctonia were isolated from stem, stolon and root material, and from tuber-borne sclerotia. These were identified using the number of nuclei per cell and anastomosis reactions. The majority (95%) of the isolates collected were multinucleate Rhizoctonia solani with a small percentage (5%) of isolates being binucleate Rhizoctonia spp. The majority (82%) of R. solani isolates were determined to belong to AG 3, with the remainder belonging to AG 4, AG 2-2 and an undetermined anastomosis group. This is the first record of R. solani belonging to anastomosis groups other than AG 3 being reported in association with potato crops in Western Australia.

Variation within the R. solani anastomosis groups identified was examined using pectic zymogram analysis. The AG 3 isolates were grouped to two zymogram patterns, corresponding to ZG 7-1 and ZG 7-2. R. solani isolates belonging to AG 2-2 also produced two zymogram patterns, with one being identified as ZG 4, and the other unidentified. All of the AG 4 isolates produced a single zymogram pattern, as did the isolates of unidentified anastomosis group.

Variation within the intraspecific groups of the R. solani isolates collected was analysed using RFLP analysis of the ITS region of the rDNA. This method of analysis differentiated between the anastomosis groups of R. solani collected, but did not detect variation within the anastomosis groups.

This study has clearly identified that Rhizoctonia disease of potatoes in Western Australia involves a combination of R. solani anastomosis groups, and subgroups. These findings may have implications in the control of Rhizoctonia disease in potatoes, and within the other crops grown in rotation with potato in Western Australia.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Biological and Environmental Sciences
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor: O'Brien, Philip, Hardy, Giles and Wright, D.
URI: http://researchrepository.murdoch.edu.au/id/eprint/32630
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