Grouping of binucleate Rhizoctonia anastomosis group D (AG-D) isolates into subgroups I and II based on whole-cell fatty acid compositions

Whole-cell fatty acid compositions of binucleate Rhizoctonia AG-D (R. cerea lis) isolates representing subgroups I [AG-D (I)] and II [AG-D (II)] obtain ed from various host plants were compared. Ten fatty acids including myrist ic (14 : 0), pentadecanoic (15 : 0), palmitic (16 : 0), palmitoleic (16 : 1 cis9), heptadecanoic (17 : 0), 9-heptadecenoic (17 1 cis9), stearic (18 : 0), oleic (18 : I cis9), linoleic (18 : 2 cis9,12) and linolenic (18 : 3 ci s9,12) were consistently present in all isolates of Rhizoctonia AG-D. The m ajor fatty acids found were palmitic, oleic and linoleic acids, comprising 88-93% of the whole-cell fatty acid content. The remaining fatty acids were present in smaller amounts ranging from 0.01 to 5.03% of the whole-cell fa tty acid content. Palmitic and oleic acids were present in approximately tw o and three times higher concentrations in isolates of AG-D (1) than in iso lates of AG-D (II), respectively. On the other hand, linoleic acid was abou t two times lower in isolates of AG-D (1) than in isolates of AG-D (II). Pr incipal component and cluster analyses of the percentage composition of fat ty acids showed distinct separation between AG-D (1) and AG-D (II). The res ults indicated that fatty acid analysis is useful for differentiating AG-D (1) and AG-D (II) and supported previous differentiation of the two subgrou ps on the basis of cultural characteristics, pathogenicity and DNA analyses . In addition, a Rhizoctonia AG-Q isolate from bentgrass and Rhizoctonia AG -D isolates causing foot rot of wheat and stem rot of mat rush were grouped in AG-D (1), based on the percentage composition of fatty acids.