Mycol. Res. 97 (9): 1056-1058 (1993) Printed in Great Britain 1056 Evidence of stability of pectic zymogram groups within Rhizoctonia solani AG-8 G. C. MACNISH 1 AND M. W. SWEETINGHAM z 1 Department of Agriculture, PMB 50, Esperance, Western Australia, 6450, Australia 2 Department of Agriculture, Baron-Hay Court, South Perth, Western Australia, 6151, Australia Within R. solani AG-8, the cause of rhizoctonia bare patch disease of cereals, legumes and pasture, five zymogram groups have been identified. Evidence is presented that demonstrates the five groups (currently designated ZG1-1, ZGl-2, ZGl-3, ZGl-4 and ZG2) are very stable. These groups have a wide distribution in the cereal growing regions of southern Australia and some have been detected in the Pacific Northwest of the U.S.A. We propose that ZG2 be renumbered as ZGl-5 to create a standard numbering system for zymogram groups within AG-8. Rhizodonia bare patch disease of cereals, legumes and pasture is caused by Rhiwctonia solani KUhn [teleomorph: Thanate- phorus cucumeris (Frank) Donk] and is an important disease in the southern cereal growing regions of Australia (Murray & Brown, 1987). This disease has also been reported from the U.K. (McKelvie, 1978) and the U.S.A (Weller et al., 1986). The pathogen was originally identified as R. solani by Samuel (1928) and was subsequently identified as a specific 'root attacking' strain by Kerr (1955). De Beer (1965) reported that he could identify two distind root-attacking strains and that these could both be present within the same crop. Neate & Warcup (1985) established that the R. solani causing rhizodonia bare patch was a unique and previously unreported Anastomosis Group that they designated AG-8. This was confirmed by Rovira, Ogoshi & McDonald (1986) in Australia and, subsequently, it was shown that R. solani AG- (a) (b) 01-2 ZGl·! ZOI-4 R, R, R 0·36 0·31 0.17 0·32 0·27 0·23 0·25 0·21 0·10 0·21 0·17 0·16 0·13 0·12 Fig. 1. (a) Pectic zymograrn patterns [using 1 in 50 dilution of culture filtrate in a gel buffer solution (Sweetingharn et al., 1986)] of two isolates of Rhizoclonia solani AG-8 zymograrn group (ZG) 1-5 (formerly ZG2), ZGl-2, ZG1-1, ZGl-4 and one representative of ZGl-3 (twice) respectively. The isolates used from left to right are 92451, 91610; 91437, 91436; 89570, 91638; 88351, 91094; 1512, 1512 respectively. (b) Main diagnostic bands for the above groups respectively and their R, values.