Jashanpreet Singh, R.U. Khan and Safdar Kaiser Hasmi
Abstract
Indian mustard (Brassica juncea L.) is one of the most significant oilseed crops cultivated across India, yet it suffers substantial yield losses due to âwhite mouldâ caused by Sclerotinia sclerotiorum. This pathogen is necrotrophic in nature and infects various plant parts, producing characteristic white cottony mycelium and hard, black sclerotia. The present investigation was conducted during the rabi season of 2020â21 to analyze the cultural and morphological variability among isolates of S. sclerotiorum under laboratory conditions. For this purpose, three isolates of the pathogen were obtained from infected rapeseedâmustard samples collected from Panjipora, Chherat, and the Department of Plant Protection farm field at AMU, Aligarh (Uttar Pradesh). Each isolate was cultured separately on Potato Dextrose Agar (PDA), and observations were recorded on radial mycelial growth, time required for initiation of sclerotia, number of sclerotia per plate, colony colour, and colony pattern at 72 and 96 hours after incubation. The results revealed significant variability among the isolates in terms of growth rate, sclerotial initiation, and colony characteristics. The Panjipora isolate exhibited the highest radial growth (74.50 mm at 72 h and full plate coverage 90.00 mm at 96 h) and produced scattered whitish colonies with 14.33 ± 0.88 sclerotia per plate. The Chherat isolate showed comparatively slower growth (69.66â90.00 mm), whitish colonies, and sclerotia arranged near the rim. The AMU farm isolate grew up to 70.00â90.00 mm, produced dirty-white colonies, and developed 17.33 sclerotia attached to the margin of the plate. The variation recorded in growth rate, colony appearance, and sclerotial formation pattern clearly indicates intraspecific diversity among the isolates of S. sclerotiorum. Such differences may play an important role in determining their adaptability and pathogenic behaviour.