COMPARISON OF WHOLE-CELL FATTY-ACID COMPOSITIONS IN INTRASPECIFIC GROUPS OF RHIZOCTONIA-SOLANI AG-1

Gas chromatography and integrated computer software (Microbial Identification System, Microbial ID, Inc., Newark, DE) were used to identify and compare fatty acid compositions among isolates representing three intraspecific groups of Rhizoctonia solani anastomosis group 1 (AG-1). The major fatty acids found, constituting 94-96% of the C9-C20 fatty acids present, were linoleic (18:2 cis 9, 12), oleic (18:1 cis 9), and palmitic (16:0). Smaller amounts of nine other fatty acids were consistently identified in preparations from 2- and 4-day-old cultures. Library entries were generated for the intraspecific groups AG-1 IA, AG-1 IB, and AG-1 IC. A dendrogram of these library entries showed that AG-1 IA and AG-1 IB are very closely related in fatty acid composition, whereas AG-1 IC is different. Intraspecific group libraries challenged with independent isolates could be used to identify most isolates of AG-1 IB and AG-1 IC but not AG-1 IA. Most of the isolates of AG-1 IA were identified as AG-1 IB.