In Vitro Evaluation of Commercial Fungicides against some of the Major Soil Borne Pathogens of Soybean

Abstract

Four Strobilurin, two premix of Strobilurin and Triazole, and one pyrazole-carboxamide foliar fungicides were tested in a modified in vitro culture plug technique against Colletotrichum truncatum (CT), Fusarium virguliforme (FV), Macrophomina phaseolina (MP), Pythium irregulare (PI), Rhizoctonia solani (RS), and Sclerotinia sclerotiorum (SS) and three Strobilurin and two premixes against Septoria glycines (SG). Under aseptic conditions, a single 6-mm culture plug of actively growing individual fungus was placed inverted on one end inside periphery of 9-cm PDA plates and on the opposite end 6-mm sterilized blotter disc with 50-μl fungicide solution was placed. Tests against SG were by spreading 50-μl spore suspension (1×108 spores/ml) on to PDA and placing blotter disc with 50-μl fungicide in the center. During 12-day incubation in 12-h photoperiod, assessed in vitro (i) effects of fungicides on growth of pathogens, (ii) sensitivity of pathogens to fungicides and (iii) persistence of fungicide tolerance in pathogens. All the fungicides except Sercadis, significantly (P<0.05) reduced radial growth of CT, while Headline EC, Priaxor and Stratego YLD significantly reduced growth of FV, MP, RS and SS. Similarly, Sercadis was effective against RS, and Aproach and Quadris against FV. SG and CT showed significant (P<0.05) sensitivity to most of the fungicides, FV, RS and SS showed significant sensitivity by forming inhibition zone between their growth ends and Headline EC, Priaxor and Stratego YLD discs. CT, MP and RS showed significant (P<0.05) persistence to all the fungicides that is considered fungistatic effect.