Ecophysiological behavior of major <i>Fusarium</i> species in response to combinations of temperature and water activity constraints

International audience

English. Fusarium head blight (FHB) is a devastating fungal disease affecting cereals, caused by Fusarium species that can produce harmful mycotoxins. Fusarium species coexist within the same ecological niche during infection, with their population dynamics and associated mycotoxin patterns strongly influenced by the environment. This study provides a comprehensive investigation of the ecophysiological responses of the major Fusarium species causing FHB under varying abiotic factors. We assessed growth and mycotoxin production of different isolates of Fusarium avenaceum, Fusarium graminearum, Fusarium langsethiae, Fusarium poae, and Fusarium tricinctum under 24 combinations of temperature (θ = 15, 20, 25, 30°C) and water activity levels (a w = 0.99, 0.98, 0.97, 0.96, 0.95, 0.94). Our findings indicated that θ, a w , and their interaction have a main significant impact on species behavior. Thanks to innovative statistical approaches using fungal growth data from optical density measurements and myco toxin quantification, we demonstrated significant inter-and intra-specific differences in environmental responses. Growth and mycotoxin production of F. graminearum and F. avenaceum appeared favored under high temperature (≥25°C) and high water activity (≥0.97), whereas lower a w levels (≥0.95) were also conducive for F. poae and F. tricinctum. A specific and unique behavior of F. langsethiae to lowest temperatures (≤20°C) was highlighted. Understanding the ecophysiological requirements of Fusarium species is crucial in the context of climate change, which is expected to worsen disease outbreaks. This study provides valuable knowledge for improving the reliability and robustness of FHB prediction models and anticipating the associated mycotoxin risk.<p>IMPORTANCE Fusarium species pose a significant threat to major cereal crops, particularly wheat, by reducing yields and producing mycotoxins that are harmful to animals and humans. The prevalence of each Fusarium species is strongly influenced by environmental conditions, and climate changes have already been reported as responsible for shifts in pathogen populations, leading to changes in mycotoxin patterns. This study revealed distinct ecophysiological behaviors, including growth and myco toxin production, of the five major Fusarium species infecting small grain cereals when exposed to varying temperature and water activity conditions. Our findings provide a valuable foundation for a deeper understanding of mycotoxin risk and for developing more effective mitigation strategies in the near future.