Characterization of Variability in Rhizoctonia solani by Using Morphological and Molecular Markers

Twenty-four isolates of Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) collected from soil, root and collar rot or foliage blight-infected plants from several locations of north India were used for the analysis of variability by using morphological and molecular markers. Among the morphological characters, variation was observed in hyphal cell size. Seventeen isolates produced few to abundant, white to dark brown or black, small to large sclerotia generally in the middle of the colony. Genetic variation was also analysed by using 11 random amplified polymorphic DNA primers (RAPD), four universal rice primers (URPs) and two inter simple sequence repeat (ISSR) markers and fingerprint patterns generated for each isolate. The size of amplified DNA bands ranged from 0.3 to 3.5 kb in all the isolates with RAPD, URP and ISSR markers. The isolates obtained from same hosts and same geographical regions showed similarity in DNA fingerprint profiles barring few exceptions. All the isolates were classified into four groups using DNA markers. A comparison of the data obtained from different markers showed that URPs are superior to RAPD, ISSR and morphological markers in detecting genetic variability among the isolates of R. solani. Hence, use of URP’s, which have long primer and higher annealing temperature, would be more sensitive and reliable markers in characterizing genetic diversity in R. solani