Understanding Colletotrichum truncatum, a Pathogen of Soybean Anthracnose, and In Vitro Efficacy of Modern Fungicides for it’s Management

Abstract

The present investigation was convened during kharif, 2023 (July–December) at J.N.K.V.V., Jabalpur, Madhya Pradesh, India to characterize the fungus isolated from Anthracnose symptomatic sample of soybean, and to assess the fungal growth medium and evaluate the effectiveness of new-generation fungicides against it. During the investigation, apart from morpho-cultural traits, Internal transcribed spacer (ITS) regions of 5.8S ribosomal DNA of pathogenic fungus were amplified using the universal primers ITS 4 and ITS 5 and sequenced. Five readymade and two modified growing media were evaluated for fungal growth and sporulation. Antifungal efficacy of ten fungicides at 10,100 and 250 µg ml^-1 were tested against pathogens by using the poisoned food technique. PCR amplification of the ITS region produced about 580 bp amplicon, and sequences of Jabalpur isolate (PP930734) showed the highest similarity of 99.12% with C. truncatum sequences at NCBI. Soybean leaf extract agar (85.10 mm), corn meal agar (83.13 mm) and potato dextrose agar (81.33 mm) were found to be significantly superior for mycelia growth, and Richard’s agar and potato dextrose agar were excellent for sporulation of C. truncatum. In vitro testing of fungicides, the percent growth inhibition of C. truncatum was significantly higher in thiophanate methyl 45%+Pyraclostrobin 5% FS (91.12%) followed by Carbendazim 12%+Mancozeb 63%WP (88.91%), Carboxin 37.5%+Thiram 37.5% DS (88.01%) and Tebuconazole 25.9 % w/w (77.00%), respectively at 250 µg ml^-1. These fungicides were also showed efficacy at lower concentrations (10 and100 µg ml^-1) and among all, copper oxychloride 50% WP was least efficient.