Pathogenicity, anastomosis groups, host range, and genetic diversity of Rhizoctonia species isolated from soybean, pea, and other crops in Alberta and Manitoba, Canada

Root rot is a common disease in soybean (Glycine max) and field pea (Pisum sativum), which restrain increased production in Canada. Sixty-seven isolates of Rhizoctonia were recovered from various diseased plants in Alberta, Canada along with three isolates from diseased soybean plants in Manitoba, Canada. According to their anastomosis behavior, 23 (32.9%) of the isolates were identified as anastomosis group (AG) 4 (AG4), 7 (10.0%) were AG2-1, 10 (14.3%) were AG2-2, 7 (10.0%) were AG5, 3 (4.3%) were AG-E and the AGs of the remaining 20 (28.6%) isolates could not be determined. Isolates belonging to AG4 produced typical symptoms of stem rot and root rot on seedlings of soybean and pea and were more aggressive than the AG2-1, AG2-2, AG5 and AG-E isolates. Selected isolates of AG4, AG2-1, AG2-2, AG5 and AG-E were to some degree able to infect common crops in Alberta, which included barley, canola, corn, faba bean, flax, lupin, lentil, pea, potato, soybean, and wheat. The genetic variability among these isolates was evaluated using phylogenetic analysis based on the rDNA ITS sequences and inter-simple sequence repeat (ISSR) markers. For the ITS sequence analysis, a neighbour-joining tree was constructed using the PAUP program, which clustered the Rhizoctonia isolates into five groups (Groups I to V). However, no correlation was observed between AGs, locations, aggressiveness or host origins. For the ISSR analysis, 54 polymorphic ISSR patterns were identified, indicating a high level of diversity among the isolates.

Automated summary

Root rot is a common disease in soybean and field pea, which limits crop production in Canada. This study identified different anastomosis groups (AGs) of Rhizoctonia isolates and evaluated their aggressiveness and genetic variability. The results showed no correlation between AGs, locations, aggressiveness, or host origins. Phylogenetic analysis and ISSR markers revealed a high level of genetic diversity among the isolates.