Shifts in Communities and Mycotoxins in Maize Residues, Soils, and Wheat Grains throughout the Wheat Cycle: Implications for Fusarium Head Blight Epidemiology.

Fusarium Head Blight (FHB), predominantly caused by species, is a devastating cereal disease worldwide. While considerable research has focused on communities in grains, less attention has been given to residues and soil, the primary inoculum sources. Knowledge of spp. diversity, dynamics, and mycotoxin accumulation in these substrates is crucial for assessing their contribution to wheat head infection and the complex interactions among communities throughout the wheat cycle. We monitored six minimum-tillage wheat fields, with maize as the preceding crop, over two years. Soils, maize residues, and wheat grains were sampled at four stages. composition was analyzed using a culture-dependent method, species-specific qPCR, and region metabarcoding sequencing, enabling species-level resolution. The communities were primarily influenced by substrate type, accounting for 35.8% of variance, followed by sampling location (8.1%) and sampling stage (3.2%). Among the 32 identified species, and dominated grains, with mean relative abundances of 47% and 29%, respectively. Conversely, residues were mainly contaminated by , with a low presence of , as confirmed by species-specific qPCR. Notably, during periods of high FHB pressure, such as in 2021, was the dominant species in grains. However, in the following year, outcompeted , resulting in reduced disease pressure, consistent with the lower pathogenicity of . Source Tracker analysis indicated that residues were a more significant source of contamination on wheat in 2021 compared to 2022, suggesting that in 2021 primarily originated from residues, whereas 's sources of infection need further investigation. Additionally, multiple mycotoxins were detected and quantified in maize residues during the wheat cycle, raising the question of their ecological role and impact on the soil microbiota.