In-vitro Assessment of Fungicides against Macrophomina phaseolina Causing Charcoal Rot in Soybean

Abstract

Background and Aim: Soybean (Glycine max (L.) Merrill), commonly known as the “golden bean,” is a globally significant leguminous crop owing to its high nutritional value and it is severely limited by various diseases, which can result in substantial yield losses. To evaluate the efficacy of newly approved and recommended fungicides against charcoal rot disease of soybean under in vitro conditions. Study Design: Complete randomized block design. Place of Study: Division of Crop Protection, ICAR-National Soybean Research Institute, Khandwa Road, Indore. Methodology: Macrophomina phaseolina was isolated from charcoal rot–infected plants and cultured on PDA. The fungus produced white to grey mycelium with black microsclerotia (80–120 µm). Pure cultures were obtained using hyphal tip transfer on PDA acidified with 0.2% lactic acid and maintained by weekly subculturing. Fungicidal efficacy was evaluated in vitro using the poison food technique with foliar fungicides (0.05–0.2%) and seed treatment fungicides (0.025–0.125%). A 4 mm mycelial disc from a 4-day-old culture was inoculated onto treated PDA plates and incubated at 26 ± 1°C. Percent mycelial growth inhibition was calculated using Vincent’s formula. Results: Fungicides, concentrations, and their interaction significantly affected mycelial growth inhibition in foliar fungicides (P < 0.0001), while seed dressing fungicides showed no significant differences. Among foliar fungicides, picoxystrobin + propiconazole was most effective, with maximum mean inhibition of 92.79%. All seed dressing fungicides showed complete (100%) inhibition of charcoal rot at all concentrations. Conclusion: Picoxystrobin + propiconazole was the most effective foliar fungicide against the charcoal rot pathogen, while all tested seed treatments achieved complete mycelial inhibition. Further field evaluations are required to confirm their effectiveness under field conditions in soybean.