Alternaria and Fusarium Fungi: Differences in Distribution and Spore Deposition in a Topographically Heterogeneous Wheat Field

Abstract

Fusarium spp. and Alternaria spp., two genera of filamentous fungi, are common colonizers of the wheat phyllosphere. Both can be pathogenic and produce mycotoxins that are harmful to consumers. Their in-field infection dynamics have been a focus for the development of new control strategies. We analysed the abundance on plant ears and spore deposition patterns of Fusarium spp. and Alternaria spp. in a topographically heterogeneous field. Abundances were assessed genetically, using qPCR-based techniques, and passive spore traps were installed for quantifying the spore deposition at different plant heights. Data loggers were placed to measure the differences in microclimate across the field. Results indicate different distribution and spore deposition patterns for the two fungi. Fusarium spp. spore and genetic abundances were higher in spots with a more humid and colder under-canopy microclimate. Alternaria spp. showed the opposite trend for genetic abundance, while its spore deposition was not correlated to any of the microclimatic conditions and was more uniform across the field. Our study extends the knowledge on the dispersal and in-field infection dynamics of Fusarium spp. and Alternaria spp., important for a better understanding of the epidemiology of these wheat pathogens. It also illustrates that topographically heterogeneous fields are a suitable environment for studying the ecology of phyllosphere-colonizing fungi.

The distribution of mycotoxins in a heterogeneous wheat field in relation to microclimate, fungal and bacterial abundance

“…Schiro et al . () observed Alternaria increasing in drier and warmer spots in a topographically heterogeneous field, while Fusarium positively correlated with humidity factors, with soil humidity being the best predictor. Our new results confirm these trends and once again underline the ecological differences between those two fungal genera, already hypothesized by Nicolaisen et al .…”

“…Regarding the genetic markers studied, we can compare our values to those obtained in our previous study conducted with a similar methodology (Schiro et al . ). There we also observed the distribution of Fusarium and Alternaria in a heterogeneous field.…”

“…DNA was extracted with the same method presented in Schiro et al . (). qPCR were performed to assess the abundance of Fusarium spp., Alternaria spp., fungal ITS abundance and trichothecene mycotoxins producers within the Fusarium family.…”

“…abundances were assessed with the same method as described by Schiro et al . (), targeting respectively the TEF‐1α elongation gene and the alt a1 gene. The Tri 5 protocol was taken from Strausbaugh et al .…”

“…Distribution differences between Alternaria and Fusarium in comparison to in‐field microclimatic conditions were also shown by Schiro et al . (). Thus, we hypothesize that such systems are helpful tools to elucidate the ecological mechanisms leading to mycotoxin synthesis.…”