Cultural and Morphological Variability among the Isolates of Sclerotium rolfsii, Causing Stem/Pod Rot of Groundnut

Eight isolates of Sclerotium rolfsii were collected during Kharif-Rabi, seasons of 2011–12, maintained and studies their cultural and morphological variations. Results revealed that all the eight isolates of S. rolfsii exhibited a great variability in respect of colony growth colour and appearance and the amount of sclerotia produced. Radial mycelial growth of the test isolates was ranged from 72.00 mm (Sr Jl) to 90.00 mm (SrNd). However, it was maximum in isolate SrNd (90.00 mm) followed by the isolates viz., SrLt (88.00 mm), SrHl (86.00 mm), SrAb (82.00 mm) and SrPb (80.00 mm). Mostly while coloured, flattened to raised colonies with smoth or wavy margin were produced. Initiation of the sclerotia was varied from 7thto 9ᵗʰ days of incubation and fair (++) to excellent (+ + + +) sclerotial formation was observed in the test isolates of S. rolfsii. All eight isolates S. rolfsii exhibited variability in respect of sclerotial size, shape, colour, number of sclerotia/plate and their test weight. However, maximum number of sclerotia were recorded with the isolate-Sr Jl (430/plate), followed by the isolates viz., SrOb (400/plate), SrNd (340/plate) and SrLt (320). Rest of the isolates recorded number of sclerotia in the range of 110 to 150/plate. Large sized sclerotia (1.8mm²) were recorded in SrNd isolate followed by SrLt (1.6 mm²) and SrHl (1.4 mm²). The isolate Sr Jl and SrOb produced comparatively very small sized sclerotia (08 and 1.0 mm²). Highest test weight (112.40 mg) was recorded in SrNd isolate, followed by the isolates viz., SrLt (98.20 mg) and SrHl (84.10 mg). Spherical, round or oval shaped sclerotia were produced by the test isolates. Colour of the sclerotia produced by the test isolates was varied from light brown to dark brown or reddish brown. Thus, present findings suggested the existence of culturally and morphologically diverse isolates amongst the S. rolfsii populations, prevailed in the Marathwada region.