Assessment of the Role of Local Strawberry Rhizosphere—Associated Streptomycetes on the Bacterially—Induced Growth and Botrytis cinerea Infection Resistance of the Fruit

Abstract

The future need for sustainable agriculture will be met in part by wider use of biological control of plant pathogens over conventional fungicides hazardous to the environment and to public health. Control strategies involving both (i) direct use of microorganisms antagonistic to the phytopathogen, and (ii) use of bioactive compounds (secondary metabolites/antibiotic compounds) from microorganisms on the phytopathogen were both adapted in order to investigate the ability of streptomycetes isolated from the rhizosphere of strawberry plants to promote the growth of the fruit and suppress Botrytis cinerea causing strawberry rot on the Sunshine Coast, Queensland, Australia. In vitro studies showed that 25/39 streptomycetes isolated from strawberry field soils inhibited B. cinerea growth by antifungal activity, ranging from antibiosis to volatile compound production. However, when non-volatile antifungal compounds were extracted and applied aerially to the actively growing strawberry fruits infected with B. cinerea, a significant disease reduction was not recorded. On the other hand, plant and fruit growth was promoted by the presence of actively growing streptomycetes in container media. Findings might indicate that live streptomycete inoculum can be used as growth promoting agent in container media for this economically important crop.