CULTURAL, MORPHOLOGICAL AND MOLECULAR VARIABILITY AMONG ISOLATES OF Rhizoctonia solani CAUSING WEB BLIGHT OF GREEN GRAM (Vigna radiata (L.) WILCZEK)
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Date
2021
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AAU, Jorhat
Abstract
Web blight of green gram is one of the major constraints which incur huge losses and hold back the production of green gram in Assam. A comprehensive study was made during 2020-21 on the variability of Rhizoctonia solani isolates based on morpho- cultural characteristics and molecular variation. Web blight infected plants were collected from different geographical locations was designated as SH-1, SH-2, AAU-1, TT-1, and MJ- 1 and identified based on a typical character with right angle branching near the distal septum of the young vegetative hyphae. A high virulence pattern for all the isolates was recorded based on pre-emergence seedling rot and complete leaf blighting appearance within 48 hours of inoculation in susceptible cultivar (SGC-16). All the five isolates showed variation in morpho-cultural characteristics such as colony growth diameter, colony texture, concentric rings on radial growth, colony color, growth pattern, hyphal width, distribution pattern of sclerotia, sclerotial initiation, maturation, color, aggregation, exudate droplets on sclerotial surface, position of sclerotia and sclerotia on lid, sclerotial diameter, number and weight in different growth media Potato Dextrose Agar (PDA), Rose Bengal Agar (RBA), Richard’s Agar (RA), Czapeck’s Dox Agar (CDA) and Sabouraud Dextrose Agar (SDA) where most of the isolates were categorized into three and four groups based on hyphal width and sclerotial initiation respectively. The size, number, and weight of sclerotia were highly variable across different isolates concerning media. They are arranged in the central, central- peripheral, sub-central, sub-central peripheral, peripheral and scattered manner on the petri- dish with respect to media.
Among different media, Sabouraud Dextrose Agar medium (85.85%) is the best growth media to study morpho-cultural variability with quantitative variables like sclerotial maturation and initiation which directly correlated with virulence of our R. solani isolates based on principal component analysis. There is no evidence of molecular variability among our isolates from different geographical locations of Assam.