Cultural and morphological variability of Rhizoctonia solani causing web blight of mungbean in Jharkhand state of India

Web blight of mungbean is one of the major diseases which incur huge loss and holds back the mung bean production. A comprehensive study was made during Kharif 2012 on the characterization of R. solani on the basis of morphology, virulence, reaction of pathogen on differential host and eco friendly management of the disease. The surveillance made revealed that the blight of mung bean was prevalent in all the places visited. The disease incidence varied from 33.10 per cent to 53.10 per cent in different localities. The pathogen R.solani was isolated from infected plants obtained from different locations and designated as RS 1 to RS 9. In the morphological study, all the isolates of R. solani shared typical characters like right angle branching near the distal septum of the young vegetative hyphe, formation of dolipore septum, no clamp connection and no conidium except moniliod cells. All the nine isolates grown on PDA showed differences in mycelial growth. RS 8 isolate showed highest growth rate after 72 hours of observation. Among nine isolates, five exhibited aerial growth of their colonies, four isolates RS 4, RS6, RS 7 and RS 9 produced sub-aerial colonies. The colony colours of RS 2, RS 6 and RS 8 isolates were brown while that of isolates RS 3, RS 5, RS 7 and Rs 9 were white. RS 1, RS 2, RS 3, RS 5, RS 6 and RS 8 isolates grew fast as well as RS 4, RS7, RS 9 grew moderately. Morphological studies of R.solani on four solid and liquid broth medium was taken PDA is the best solid medium for R. solani followed by Czapek's medium while in case of Czapek's broth is best for growth of R. solani. Sclerotial charcters indicated that in 3 isolates sclerotia were located on surface of colony, subsurface location of sclerotia was observed in RS 6 and RS 9 isolates and in RS 1, RS 3, Rs 4, RS 7 sclerotia were embedded inside medium. Sclerotial size was invariably macro except RS 2, RS 6 and RS 9. The maximum sclerotia size 2.960 mm was observed in PDA medium. Out of 15 mungbean varieties, one HUM-1 showed resistant reaction, one PDM 54 showed moderately resistant reaction, six variety showed susceptible reaction and seven variety showed highly susceptible reaction.