Biennial survey of freshly harvested maize grain mycobiota in northeastern Spain: identification, incidence, and interaction patterns

Climate change is reshaping fungal communities associated with maize, creating new risks for food safety and crop productivity. Hotter and drier summers favour xerophilic fungi, while wetter conditions promote hydrophilic ones. This study aimed to characterize fungal populations colonizing maize grains in Spain during 2023-2024 harvesting seasons, and to evaluate the influence of kernel type on fungal incidence. Ninety-one maize samples were collected in northeastern Spain. Kernels were disinfected, plated on Malachite Green and Potato Dextrose agars, and incubated for mould morphological classification. Molecular identification was performed for isolates from the two major genera observed: Fusarium and Aspergillus. Results revealed major shifts in fungal incidence between seasons. In 2023, hotter and drier conditions favoured a codominance of Fusarium spp. and Aspergillus spp. (both ∼40% infected samples). In contrast, the wetter 2024 season reduced Aspergillus spp. incidence to <5%, while Fusarium spp. maintained their dominance, accompanied by increases of Epicoccum spp. (+15.3%) and Phoma spp. (+6.2%). Fusarium proliferatum was unexpectedly the most frequent Fusarium species, surpassing Fusarium verticillioides. Aspergillus sections Flavi and Nigri reached similar levels, with Aspergillus flavus/oryzae as the main species. Popcorn was significantly more susceptible to Aspergillus spp., while there was no significant difference for the other maize types. Overall, these findings demonstrate how weather variability and kernel traits can reshape maize mycobiota. Continuous monitoring is therefore needed to anticipate shifts in fungal dominance and assure food safety and crop production under the current climate change scenario.