Anastomosis Groups, Pathogenicity, and Other Characteristics of Rhizoctonia solani Isolated from Potatoes in Peru

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Abstract
Rhizoctonia solani isolates were recovered from stem lesions and sclerotia on tubers of potato [Solanum tuberosum] plants at three agroecological zones of Peru: coastal valleys (150-270 m elevation), highland valleys (2,460-3,600 m elevation), and eastern slopes of the Andes (850 m elevation). Most R. solani isolates recovered belonged to anastomosis group (AG)-3 and AG-4, the first in the highlands (cool environment) and the second in the coast and eastern slopes of the Andes (warm environment). Pathogenicity of AG isolates was determined by planting true potato seed and tubers in soil infested with R. solani isolates at low (9-18 C) and high (18-24 C) temperatures. The highest percentage of damping-off occurred among seedlings in soil infested with AG-4 isolates at both temperature regimes. However, percent of seedling damping-off in soil infested with AG-4 isolates at both temperature regimes. However, percent of seedling damping-off in soil infested with AG-4 isolates was approximately 50% higher at high temperature than at low temperature. A similar response was obtained with AG-3 isolates.