Introduction
Rhizoctonia solani Kühn (teleomorph: Thana-
tephorus cucumeris [A.B. Frank) Donk.]) is a wide-
spread soil-borne pathogen that causes economi-
cally important diseases in many crops (Adams,
1988). Rice sheath blight caused by R. solani is
one of the most serious diseases of rice worldwide,
causing considerable yield losses (Sudhakar et al.,
1998). The widespread adoption of new, suscepti-