Microbial Interactions & Microbial Ecology

Biography

Biography: Jungkwan Lee

Abstract

The air-borne ascomycete fungus Fusarium graminearum causes head blight in many cereals and produces mycotoxins such as trichothecenes and zearalenone. The seed-borne bacterium Burkholderia glumae causes bacterial panicle blight in rice and produces toxolavin that has antimicrobial activity and phytotoxicity. Disease symptoms caused by two pathogens are very similar and could often cause false diagnosis. In this study, we showed that two pathogens frequently co-isolated in rice heads and F. graminearum is resistant to toxoflavin produced by B. glumae while other fungal genera are sensitive to the toxin. We have tried to clarify the resistant mechanism of F. graminearum against toxoflavin and the ecological reason of co-existence of the two pathogens in rice. We found that F. graminearum resistance to toxoflavin is related to production of triacylglycerides containing linolenic acid. Co-cultivation of two pathogens resulted in increased conidia and trichothecene by F. graminearum. Bacteria physically attached to fungal conidia, which protected bacterium cells from UV light and allowed disease dispersal. Chemotaxis analysis showed that bacterial cells moved toward the fungal exudation. Disease severity on rice heads was significantly increased by co-inoculation rather than single inoculation. This study provides evidence of the two pathogens cooperatively interacting, with F. gramienarum gaining the opportunity to induce disease progression efficiently and B. glumae achieving aerial dispersal.