Efficacy of antifungal substances of three Streptomyces spp. against different plant pathogenic fungi

Abstract

BackgroundSoil-borne plant pathogenic fungi with a wide host range of crops cause a significant limitation on the global production of agronomic crops. Applications of synthetic pesticides are an important tool for managing plant diseases, but have deleterious influences on the environment as well as its incompatibility with organic agriculture. Recently, Streptomyces spp. became one of the best bio-control agents as a promising environmentally eco-friendly method for effective management of plant diseases.ResultsIn a previous research, three species of Streptomyces spp., i.e., S. griseus (MT210913 “DG5”), S. rochei (MN700192 “DG4”) and S. sampsonii (MN700191 “DG1” strains) were identified, as exhibiting potent antifungal activities against plant pathogenic fungus, Sclerotinia sclerotiorum in vitro and greenhouse. GC–Mass analysis revealed the presence of 44, 47 and 54 substances of S. sampsonii DG1, S. griseus DG5 and S. rochei DG4, respectively. GC–MS revealed substances, with bio-control activity, were categorized as volatile organic compounds (VOCs), fatty acids and plant growth regulators, etc. GC–MS analysis exhibited the presence of 7, 13 and 20 volatile compounds produced by S. sampsonii, S. rochei and S. griseus, respectively. These substances exhibited potent antifungal activity against various plant pathogenic fungi, i.e., Botrytis cinerea, Macrophomina phaseolina, Rhizoctonia solani and S. sclerotiorum in vitro, by dual-culture assay. The three strains inhibited all the pathogenic fungi in dual-culture assay in the range of 30–73.67%. Also, the produced substances were applied in vivo (in the field) and supported their potential biocontrol agent against S. sclerotiorum as well as possessed significant biological properties for plant health and growth. Applying Streptomyces spp. culture broth in the field enhanced physiological responses of phenols, sugar, chlorophyll, protein contents and parameters as well as the yield of bean plants.ConclusionIn field experiments, foliar application of Streptomyces spp. and their metabolites proved to be a great potential, as promising biocontrol agents, for controlling S. sclerotiorum and enhanced plant growth and yield. S. rochei and S. griseus proved to be strong antifungal, plant growth promoters and environmentally eco-friendly fungicides.