Cultural, morphological and physiological variations among different anastomosis groups of Rhizoctonia solani Kuhn in Himachal Pradesh

All the forty isolates of Rhizoctonia solani isolated from different hosts across himachal Pradesh exhibited variation in respect of cultural, morphological, physiological characteristics and anastomosis behaviour. Depending upon their anastomosis behavior, cereal isolates were assigned to AG 1-IA, solanaceous isolates AG 3, crucifer isolates AG 2–1 and legume isolates were assigned to AG 1-IB. Most of the isolates produced appressed off-white to light brown mycelium with varied patterns of sclerotial formation. Isolates produced sclerotia of varying size ranging between 1–5 mm, <1 and > 5 mm which were either present at the centre or periphery, scattered throughout the colony or in concentric rings. cereal (AG 1-IA) isolates exhibited the highest number of nuclei per hyphal cell while legume (AG 1-IB) isolates possessed the maximum hyphal width. Though all the isolates exhibited little variations in their growth rates, studies indicated that a temperature range between 25 and 30°C was the most suitable for optimal growth of isolates. However, cereal (AG 1-IA) isolates exhibited maximum growth both at 25 and 30°C temperatures with 1.56 and 1.51 mm/h growth rates, respectively.