Rhizoctonia spp. cause shoot and leaf blight of eucalyptus in clonal hedges as well as cuttings. Despite the importance of Rhizoctonia spp. to eucalyptus, little is known about their diversity. Thus, we characterized isolates and report new anastomosis groups in a eucalyptus clonal hedge. Isolates obtained at different stages of cutting propagation were characterized according to the number of nuclei in vegetative cells, grouped by morphological characteristics of the colony, anastomosis group, and thiamine auxotrophism. The isolates were also evaluated for virulence on eucalyptus and effect of temperature on their mycelial growth. No correlation between morphological grouping and anastomosis reaction was detected. A wide range of isolates, predominantly binucleate, forms the population of Rhizoctonia spp. present in the soil of clonal hedges, which differed in virulence to eucalyptus. Binucleate and multinucleate isolates had similar growth features at different temperatures, with an optimum growth rate between 25-30 ºC. Isolates of R. solani AG2-2 IIIB and binucleate isolates of Rhizoctonia spp., AG-P and AG-O, as agents of cutting rot, and binucleate isolates AG-A and AG-L in the soil of eucalyptus clonal hedge are reported for the first time.
Rhizoctonia solani; Eucalyptus; etiology; leaf blight
