Abstract

                                The present investigation was carried out to study the variability among R. bataticola isolates causing root rot disease of pigeonpea in Tamil Nadu. Totally 10 isolates of the fungus wererecovered from different pigeonpea growing regions of Tamil Nadu. Morphological observation revealed the occurrence of variation with respect to colony type, growth pattern, and size and shape of microsclerotia. Based on morphology, the isolates were grouped into two morphological catagories viz., isolates with appressed type growth (I) and fluffy type growth (II). The size of microsclerotia varied from 87.6 x 79.2 µm to 146.3 x 133.9 µm. All the isolates were analyzed through RAPD-PCR for genetic diversity. The UPGMA cluster analysis identified four main groups. Similarity matrix and Jaccard’s similarity co-efficient between the isolates indicated the maximum genetic variation of 43 per cent among the isolates from Vellore and Thiruvannamalai districts. Maximum similarity of 92 per cent was recorded between the isolates from Erode and Salem. The results demonstrated existence of variability within R. bataticola isolates causing pigeonpea root rot and thereby can be used for developing management strategies.

Key words : Pigeonpea, Root rot, Rhizoctonia bataticola, RAPD, Variability