Differentiation of Rhizoctonia AG-D isolates from turfgrass into subgroupsI and II based on rDNA and RAPD analyses

Binucleate Rhizoctonia anastomosis group (AG) D is the cause of rhizoctonia -patch and elephant-footprint diseases of zoysiagrass, and winter-patch dis ease of bentgrass. Rhizoctonia AG-D is also known as the causal pathogen of other diseases such as sharp-eye-spot of cereals, foot-rot of cereals and winter-stem-rot of mat rush. Isolates of AG-D have been divided into the tw o subgroups AG-D (I) and AG-D (II), based on the results of cultural charac teristics and pathogenicity tests. Isolates obtained from zoysiagrass exhib iting symptoms of rhizoctonia-patch disease, from bentgrass with winter-pat ch disease, from wheat with foot-rot disease, and from mat rush with winter -stem-rot disease were reported to belong to subgroup AG-D (I). On the othe r hand, isolates obtained from zoysiagrass with elephant-footprint disease were assigned to subgroup AG-D (II). To confirm the existence of these two subgroups in AG-D, the genetic structure of AG-D isolates from turfgrass an d other crops was compared. RFLP analysis of the ITS region from rDNA after digestion with the restriction enzymes EcoRI, HaeIII, HhaI, HinfI, and Mbo I separated AG-D isolates into two groups corresponding to AG-D (I) and AG- D (II). Furthermore, other AGs except AG-Q (AGs-A, Ba, Bb, C, E, F, G, I, K , L, O, P, and R. solani AG1-IC) did not have the same patterns that were s een for the two AG-D subgroups. AG-Q isolates from bentgrass showed the sam e patterns as AG-D (I). The results of the RAPD analysis also revealed the existence of two groups that corresponded to AG-D (I) and AG-D (II). These analyses revealed that Rhizoctonia AG-D isolates from turfgrass could be di vided into two subgroups consistent with those based on cultural characteri stics and pathogenicity. In addition, isolates of foot-rot disease of wheat and isolates of winter-stem-rot disease of mat rush whose cultural charact eristics were the same as those of AG-D (I) also showed similar RFLP and RA PD patterns to those of AG-D (I) isolates from turfgrass.