Evaluating the Efficacy of Fungicides against Macrophomina phaseolina, Causing Charcoal Rot of Soybean under in-vitro Conditions

Abstract

Soybean (Glycine max (L.) Merrill) is a major oil-seed crop of global importance, but its productivity is severely threatened by charcoal rot caused by Macrophomina phaseolina, a necrotrophic fungus with a wide host range. The ITS region of the pathogen was amplified which yielded a 598 bp sequence and showed 97.15% identity and 100% query coverage in BLAST analysis. Following molecular confirmation, the in-vitro efficacy of twelve fungicides, comprising six single compounds and six combinations was assessed against M. phaseolina using the poisoned food technique at 100, 250 and 500 ppm. All tested fungicides significantly inhibited mycelial growth relative to the untreated control, though performance varied across treatments. Complete suppression (100% inhibition) was consistently recorded with Carbendazim 25% + Mancozeb 50% WS, Carbendazim 50% WP and Tebuconazole 25.9% w/w EC at all concentrations. In contrast, Penflufen 13.28% + Trifloxystrobin 13.28% FS and Azoxystrobin 11% + Tebuconazole 18.3% SC were the least effective with 61.18% inhibition at 100 ppm. The findings highlight the superior efficacy of benzimidazole and triazole based fungicides, alone or in combination with contact fungicides, for effective suppression of M. phaseolina. These results provide valuable insights for developing effective fungicidal strategies for the management of charcoal rot in soybean under field conditions.