Efficient biological control of fungal plant diseases by Streptomyces rimosus DSMZ 12424

Abstract

The actinomycete Streptomyces sp. DSMZ 12424 (HRO71) was originally isolated from the rhizosphere of strawberry and shown to be an effective antagonist in vitro toward several plant pathogenic fungi. Mechanisms of fungal inhibition were elucidated by tracing secondary-metabolite production and fungal cell wall-degrading activity. Streptomyces sp. DSMZ 12424 produced siderophores and antibiotics and showed chitinolytic activity. Additionally, the production of the plant growth hormone indole-3-acetic acid was found. When Streptomyces spores were used to coat sugar beet seeds, the emergence rate of treated plants in soil infested by Rhizoctonia solani and Pythium ultimum in comparison to the untreated control was enhanced. The bacterium was able to suppress plant pathogenic fungi in different pathosystems: (a) sugar beet - Rhizoctonia solani, (b) lambs lettuce - Phoma valerianellae and, (c) cress - Alternaria sp. DSMZ 12424 was added using seed coating (a) and seed infiltrating techniques (b, c). The biocontrol agent was formulated as water dispersable granules. The spores are conserved in the product and they can be stored at least 1 year without significant loss of activity. Finally, on the basis of Streptomyces sp. DSMZ 12424 a microbial product was developed and called Rhizovit®.