At The Scene Of The Crime: New Insights Into The Role Of Weakly Pathogenic Members Of The Fusarium Head Blight Disease Complex

Plant diseases are often caused by a consortium of pathogens competing with one another to gain a foothold in the infection niche. Nevertheless, studies are often limited to a single pathogen on its host. In Europe, fusarium head blight (FHB) of wheat is caused by multipleFusariumspecies, includingFusariumgraminearumandF. poae. Here, we combined a time series of (co)inoculations, monitored by multispectral imaging, transcriptional, and mycotoxin analyses, to study the temporal interaction between both species and wheat. Our results showed coinoculation ofF. graminearumandF. poaeinhibited symptom development but did not alter mycotoxin accumulation compared to a single inoculation withF. graminearum. In contrast, preinoculation ofF. poaereduced both FHB symptoms and mycotoxin levels compared to a singleF. graminearuminfection. Interestingly,F. poaeexhibited increased growth in dual infections, demonstrating that this weak pathogen takes advantage of its co-occurrence withF. graminearum. Quantitative reverse transcription PCR revealed thatF. poaeinducesLOXandICSgene expression in wheat. We hypothesize that the early induction of salicylic and jasmonic acid-related defences byF. poaehampers a subsequentF. graminearuminfection. This study is the first to report on the defence mechanisms of the plant involved in a tripartite interaction between two species of a disease complex and their host.