Suppression of Fusarium dry rot of potato using beneficial bacterial treatments

Abstract

Fusarium dry rot affects up to 60% of potato tubers during storage. Pathogen resistance development to synthetic chemical fungicides is a main contributing factor. Previous work has demonstrated the use of bacterial antagonists against plant pathogens. In this study, bacteria isolated from disease suppressive composts were tested to evaluate their antagonistic activity against F. sambucinum in vitro, as well as to assess their ability to reduce Fusarium dry rot of potato tubers. To identify the potential implication of antifungal compounds in their inhibitory activity, bacterial extracts were produced and assayed against F. sambucinum mycelial growth and conidial germination. In vitro results showed that all tested bacteria suppressed F. sambucinum mycelial growth over six days of incubation. When testing the bacteria against potato dry rot, 30 of 32 bacteria reduced the symptoms of the disease at the higher bacterial concentration tested. The combined in vitro and in vivo studies indicated Bacillus subtilis B9–8, Pseudomonas moraviensis F9–6, Pseudomonas koreensis F9–9, and Pseudomonas gessardii M9–16 were the most effective strains. Extracts from these four bacteria were able to inhibit mycelial growth and/or conidial germination of the fungal mold. Results from this study suggests that multiple antagonistic bacteria may be useful in controlling Fusarium dry rot on potato tubers. Extracts from the four most effective bacteria indicated that antibiosis was a main mode of action against F. sambucinum.