Pathogenicity and genetic diversity of Rhizoctonia solani isolates from lupin and other crops in Alberta, Canada

Narrow-leaved lupin (Lupinus angustifolius) is a potentially important crop in Canada. During the summers of 2003, 2004, and 2007, a total of 78 isolates of Rhizoctonia solani were isolates from diseased lupin plants and various other crops in Alberta, Canada. When the isolates were assigned to anastomosis groups (AGs) according to anastomosis behaviour, 33 (42.3%) of the isolates were identified as AG-4, 21 (26.9%) were AG-2-1, 20 (25.6%) were AG-2-2, and 4 isolates were not determined. Isolates belonging to AG-4 produced typical symptoms of stem rot and root rot on lupin seedlings and showed greater virulence compared with AG-2-1 and AG-2-2 isolates. The genetic variability among these isolates was evaluated by phylogenetic analysis based on the ribosomal DNA internal transcribed spacer (ITS) sequences and random amplified polymorphic DNA (RAPD) markers. For the ITS sequence analysis, a neighbour-joining tree, which was constructed using the PAUP program, clustered the R. solani isolates into three groups (groups I-III). Based on the phylogenetic analysis, ITS sequences were unsuitable for distinguishing the AG-2-1 and AG-2-2 isolates of R. solani but were valuable for identifying the AG-4 isolates. For the RAPD analysis, 62 polymorphic RAPD-phenotypes were identified, indicating a high level of diversity among the isolates. Based on analysis with the POPGENE program, all the isolates were clustered into five groups (groups I-V). This grouping was not closely associated with location, AG, or virulence.