Streptomycestes against fusaria: Limiting toxin production and fungal growth

Fusarium Head Blight is a disease caused by different Fusarium species on small-grain cereals, reducing yield and affecting quality of the grains. In addition, grains can be contaminated by mycotoxins, among them trichothecenes, which can lead to several problems for human and animal health. Within an integrated pest management strategy, the use of biocontrol agents is a promising approach. The aim of this research was to characterize and select potential biocontrol agents belonging to the genus Streptomyces, isolated from soil or roots of various crops, in order to discover strains able to inhibit the growth and toxin production of eight strains (covering geographic and toxigenic diversity) of Fusarium graminearum and F. culmorum. The antagonistic activities of 47 isolated bacterial strains against the pathogenic fusaria were firstly investigated by a dual-culture plate method, using different media. Eighteen strains exhibited >50% growth inhibition in at least one media. The higher inhibition percentages ranged, depending on the medium, between 55 and 79%. The most promising isolates were identified by sequencing of 16S rDNA. Eventually, the strains showing the most consistent antagonistic activity were chosen to assess their plant growth promoting activity and their influence on the disease severity in wheat seedlings. The identification of the molecules involved in toxin regulation and fungal inhibition is foreseen. The obtained results are promising and confirm the interest to investigate natural diversity of actinomycetes for identifying novel methods to reduce mycotoxin production in the cereal-Fusarium spp. pathosystem.