Exploring Myxomycetes for possible applications as antagonists in biocontrol of plant pathogens

Myxomycetes or slime moulds are a class of Amoebozoa of which only few practical applications are published in literature. Here we report the first results towards the use of selected slime mould species as antagonists in agricultural applications. Antagonists are organisms used to control plant pathogens, protecting the plant host against invasion by bacteria and fungi. Mycotoxigenic fungi from the genera Fusarium, Aspergillus, Penicillium and Alternaria as well as selected plant pathogenic bacteria were used in the tests. Myxomycetes were collected from maize plants in 2015 and 2016 at the end of the growth season. Five different species including soil-borne Physarum and Didymium spp. were identified. It was demonstrated that these slime moulds can have at least 3 different known types of antagonism: 1) direct antagonism due to feeding (phagocytosis) on fungal spores and plant pathogenic bacteria, 2) indirect antagonism due to antibiotic and antimycotic activity in the glycocalyx and solubilisation of fungal mycelium using extracellular lytic enzymes, and 3) competition for feed such as plant pollen which are important nutrient sources for specific plant pathogens (e.g. Fusarium species) during plant infection.
A further step required for practical applications is the production of sufficient biomass for field tests. Three long-lived stages including spores, microcysts and sclerotia (macrocysts) would be suitable for practical use since they have a shelf-life of at least 2 years.
Several possible applications are investigated. We check the use of slime moulds for biological seed dressing. After sowing the slime mould should protect the seed and the young seedling against invasion by soil-born plant pathogens (fungi and bacteria). In a further approach the antagonistic activity of soil-born myxomycetes will be tested on crop debris colonized with Fusarium spp. On these plant residues Fusarium spp. produce spores which infect small grain cereals in the next growth season. The ultimate goal is to cut the life cycle of the plant pathogen.

Publication year:2018