Determination of Whole-Cell Fatty Acid Profiles for the Characterization and Differentiation of Isolates of Rhizoctonia solani AG-4 And AG-7

Abstract

Fatty acid methyl esters (FAMEs) of isolates of Rhizoctonia solani AG-4 and AG-7 were characterized by gas chromatography and analyzed with Microbial Identification System software. Palmitic, stearic, and oleic acids were common in all isolates from both anastomosis groups (AGs) and accounted for 95% of the C14 to C18 fatty acids present. Oleic acid, most common in both R. solani AG-4 and AG-7 isolates, accounted for the greatest percentages of total FAMEs. The presence, quantities, or absence of individual fatty acids could not be used for distinguishing AG-4 and AG-7 isolates. Anteisopentadecanoic and 9-heptadecanoic acids, however, were specific to all three AG-7 isolates from Japan but absent in other AG-7 isolates and all AG-4 isolates. Pentadecanoic acid occurred in only two of the R. solani AG-4 isolates, but was not found in any of the AG-7 isolates. The AG-4 isolates could be distinguished from AG-7 isolates when quantities of FAMEs and key FAME ratios were analyzed with cluster analysis and principle components were plotted. Isolates of AG-7 from Arkansas, Indiana, and Georgia appeared to be more closely related to each other than to AG-7 isolates from Japan and Mexico. These differences in FAMEs were sufficiently distinct that isolate geographical variability could be determined. A dendrogram analysis cluster constructed from the FAMEs data showed results similar to that of the principal component analysis. Euclidean distances of total AG-4 isolates were distinct from total AG-7 isolates. The Arkansas and Indiana AG-7 isolates had a similar Euclidean distance to each another but the percentages were different for the AG-7 isolates from Japan and Mexico. In conclusion, variability of the FAMEs identified in this study would not be suitable as the main diagnostic tool for distinguishing individual isolates of R. solaniAG-4 from AG-7.

Comparison of Whole‐Cell Fatty Acid Compositions of Isolates of Rhizoctonia solani AG 2 from Tobacco and Tulip, AG 2–1 and AG‐BI

“…Fatty acid analysis also differentiated AG 1‐IC from AG 1‐IA and AG 1‐IB but not AG 1‐IA from AG 1‐IB (Stevens‐Johnk and Jones, 1994). Isolates of AG 4 were differentiated from AG 7 using fatty acid technique, however, the differences were not as distinctive as in the previous studies (Baird et al., 2000).…”

The advancing identification and classification of Rhizoctonia spp. using molecular and biotechnological methods compared with the classical anastomosis grouping

“…AG 9 has been divided into two subgroups, but there were not sufficient available sequences in GenBank to divide this group in the present analysis. AG7 may also include at least two subgroups (Kuninaga, unpublished data), corresponding with the Stuttgart group and the pine tree group based on anastomosis reaction and the whole-cell fatty acid composition (Baird et al 2000). This result indicates differences in genetic diversity within an AG in different AGs.…”

“…However, this method was not sufficiently accurate to distinguish between isolates of AG 4 and AG 7 (Baird et al 2000). Clustal analysis of all fatty acids of isolates of three varieties of Waitea (Rhizoctonia) circinata clearly separated them into three distinct groups (Priyatmojo et al 2002a).…”

Differentiation of Three Varieties of Rhizoctonia circinata; var. circinata, var. oryzae and var. zeae on the Basis of Cellular Fatty Acid Composition

“…Many methods including nutritional test (Ogoshi and Ui, 1979), molecular (Jabaji‐Hare et al., 1990; Duncan et al., 1993; Keijer et al., 1996) and biochemical techniques (Kelens and Peumans, 1991; Stevens‐Johnk and Jones, 1993; Matsumoto and Matsuyama, 1999) have been developed to differentiate Rhizoctonia spp. One of the most promising methods is analysis of qualitative and quantitative differences in fatty acid compositions (Stevens‐Johnk et al., 1993; Stevens‐Johnk and Jones, 1994; Matsumoto et al., 1997; Baird et al., 2000). Isolates of Rhizoctonia solani AG 2 representing AG 2–1, AG 2–2 IIIB, AG 2–2 IV, AG 2–2 LP and AG 2–3 have been clearly differentiated using fatty acid analysis (Stevens‐Johnk and Jones, 1993; Matsumoto and Matsuyama, 1999).…”