From laboratory to field: applying the Fo47 biocontrol strain in potato fields

Endophytic microbes conferring biocontrol are an eco-friendly alternative to control diseases in crops. Unfortunately, the use of endophytes to control diseases is not yet widespread as their application in agricultural settings is challenging and the outcome variable. Translating strains that perform well under laboratory conditions to the field poses several challenges. One is large scale inoculum production in a cost-effective manner. Here, we developed a framework to scale up inoculum production of Fusarium oxysporum 47 (Fo47), assess inoculum viability and its performance in the field and effects on potato yield and performance. The Fo47 endophyte is a well-described biocontrol agent, isolated from disease suppressive soils in the 1980’s. Using mung bean medium, we could routinely produce ≈7 × 108 spores/mL. Using 60 mL of 107 spores/mL per tuber we could re-isolate the fungus 79 days after application from 60 to 70% of the inoculated plants in a large-scale potato field trial (Clenze, Germany). Furthermore, this protocol can be used to assess Fo47 biocontrol potential under field conditions. The presence of the fungus did not negatively affect plant yield or starch production and did not increase susceptibility to endemic pathogens.