Morphological and molecular diversity in Sclerotium rolfsii Sacc., infecting groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is an oilseed crop largely grown throughout the world. Ten isolates of S. rolfsii collected from groundnut grown areas were investigated for their morphological and genetic variability study. Based on morphological variability study, all isolates were divided in six groups based on sclerotia distribution pattern. Isolates produced number of sclerotia in range of 115–375 in light dark brown to dark brown colour while weight of hundred sclerotia and sizes of sclerotia was in range of 85.54–145.13 mg and 0.32–0.68 mm. Genetic diversity was studied through ITS amplification that produced rDNA amplicon size of 650–700 bp which confirmed that all isolates belong to Sclerotium rolfsii. RAPD primers confirmed genetic variation among the isolates. Highest numbers of amplicons (13) were observed in the OPA-9 primer. 102 polymorphic and 3 monomorphic bands were produced by RAPD primers. Isolates SrA-SrH (0.575), SrBKN-SrA (0.384) and SrBKN-SrBKL (0.330) exhibited highest similarity coefficient. Based on dendrogram generated by UPGMA, SrBKN, SrA, SrH, SrJPF, SrJPP and SrT isolates were considered in Group I. SrBKL showed highest (51%) diversity in Group II while Churu (SrC) isolate showed 49% diversity in Group III. Dendrogram and cluster analysis cleared that Group I was more genetically diverse among the isolates. Morphological and molecular diagnosis of the pathogen has a pivotal role in the implementation of chemical (fungicide) and biological (bio-agents) methods.