Relationship of binucleate Rhizoctonia isolates used for biocontrol of rhizoctonia crown rot of sugar beet to anastomosis systems

Abstract

The relationships of 10 binucleate Rhizoctonia isolates used as biocontrol agents of rhizoctonia crown and root rot of sugar beet in Ohio to described binucleate Rhizoctonia anastomosis systems were investigated. Ten Ohio binucleate Rhizoctonia (Ohio BNR) isolates, paired in all combinations, cross anastomosed with one another, indicating that all belong to the same anastomosis group. Four representative Ohio BNR isolates failed to anastomose with any tester isolates of the Ceratobasidium anastomosis grouping system, indicating that none belong in that system. However, all 10 Ohio BNR isolates anastomosed with an AG-B (o) tester isolate (binucleate Rhizoctonia anastomosis grouping system), indicating that the Ohio agents belong in this anastomosis grouping system and to the (o) intraspecific group of AG-B. None of the Ohio BNR isolates anastomosed with either of the other two intraspecific group tester isolates (AG-Ba, AG-Bb) of the AG-B group. Moreover, the AG-B intraspecific group tester isolates, AG-Ba, AG-Bb, AG-B (o), self-anastomosed but did not cross anastomose with one another. Variations in cultural characteristics noted among the 10 Ohio BNR isolates indicated that considerable heterogeneity exists within these AG-B (o) isolates. Key words: binucleate Rhizoctonia, anastomosis, rhizoctonia crown rot, sugar beet.