Prevalence of Collar Rot of Tomato Caused by Sclerotium rolfsii (Sacc.) under the Red and Lateritic Zone of West Bengal

Abstract

An experiment was carried out to study the cultural, morphological, and pathogenic variability of different isolates of Sclerotium rolfsii infecting tomato crop under the undulating red and lateritic zone of West Bengal. Cultural and morphological variability of isolates were studied based on their mycelial growth rate, colony colour, mycelial dispersion and appearance and sclerotia formation, colour, weight and number of sclerotia, arrangement and maturity days of sclerotia using potato dextrose agar medium. Pathogenic variability was studied based on pathogenicity test and host range study by soil infestation method. All the ten isolates of S. rolfsii expressed significant differences with respect to cultural, morphological, and pathogenic characters. In pathogenicity test, all the isolates showed their pathogenic temperament to tomato plant where as in host range study, all test crop species showed susceptible except wheat (Triticum vulgare) showed some extent of resistance. Three isolates were found to be very fast growing (diam. > 9 cm), three were fast growing (8-8.9 cm), three moderately fast growing (5-6 cm) and one was observed slow growing (< 3 cm). Four isolates were white, one each of extra white and cottony white, two isolates were light white and another two were dull white. The colour of sclerotia ranged from brown to dark brown, shape ranged from spherical to oval and also irregular, sclerotial weight ranged from 3.7 to 8.6 mg. Six isolates were observed scattered, two peripheral and two were reported be central in Sclerotia arrangement. Sclerotia took a range of 9 to 15 days after inoculation for maturity. A range of 154.0 to 395.0 sclerotia production per plate was reported from the tested isolates. Introduction