DNA Base Sequence Homology in Rhizoctonia solani Kühn

II. Genetic relatedness within anastomosis group 2

Abstract

DNA base sequence homology among AG-2 group isolates of Rhizoctonia solani was investigated on the basis of DNA-DNA reassociation kinetics, and the genetic relationship among pathological types was examined. DNA homology value among isolates within each single type was 100.3% with the winter crops type (II), 98.1% with the rush type (IIIB) and 100.1% with the root rot type (IV). Comparatively high values of DNA homology ranging from 68.6 to 71.5% were observed between rush type isolates and root rot type isolates, both belonging to AG-2-2. DNA homology values of winter crops type isolates of AG-2-1 with rush type isolates of AG-2-2 was 37.6 to 40.1%, and 43.5 to 49.4% with root rot type isolates of AG-2-2. These results suggested that each pathological type in AG-2 is genetically homogenous, and that between the rush type and the root rot type of AG-2-2 there is a small but significant partial heterogeneity. AG-2-1 and AG-2-2 may form genetically distinct groups.