CHARACTERIZATION, VIRULENCE, AND GENETIC-VARIATION OF RHIZOCTONIA-SOLANI AG-9 IN ALBERTA

A total of 130 Rhizoctonia solani AG-9 isolates were isolated from agr icultural soils collected in 1992 and 1993 in central and northeastern Alberta. On potato dextrose agar, cultures developed a brown to tan m ycelium and irregularly shaped, brown to dark brown sclerotia (0.5 to 2.0 mm), singly or in clamps. Number of nuclei per vegetative hyphal c ell ranged from 3 to 17. Less than 20% of the isolates were thiamine a uxotrophic. In a petri plate test, all isolates were virulent to canol a, causing seed rot and seedling infection. In a greenhouse test, AG-9 isolates were mildly virulent to canola. Two isolates were further te sted for virulence to 10 different crops. These isolates were highly v irulent to cauliflower and moderately virulent to flax, causing signif icant pre-emergence damping-off. Isolates of AG-9 also were mildly vir ulent to canola in which emergence was reduced and root discoloration was observed. Isolates were avirulent to alfalfa, pea, tomato, wheat, barley, oat, and bromegrass, though slight root discoloration on seedl ings of alfalfa, wheat, oat, and bromegrass was observed. Genetic vari ation of 12 isolates from Alberta and 3 from Alaska was analyzed by ra ndom amplified polymorphic DNA (RAPD) assay using different oligonucle otide primers. There was considerable variation within the R. solani A G-9 group; this suggests that AG-9, considered indigenous to Alaska, i s present in a variety of environments and different geographic areas. It is a heterogeneous group and the genetic variation within the AG-9 group can be identified by the RAPD-polymerase chain reaction techniq ue.