Temporal and spatial dynamics of <i>Fusarium graminearum</i> species complex associated with Fusarium head blight in wheat from 2014 to 2023 in Mexico

Fusarium head blight (FHB) is a major wheat disease worldwide and is caused by multiple species of the Fusarium graminearum species complex (FGSC). In this study, we investigated the spatiotemporal dynamics of FGSC associated with Fusarium head blight (FHB) in wheat in Mexico from 2014 to 2023 by species and trichothecene chemotype characterization, ELISA-based mycotoxin quantification, and greenhouse virulence testing. A total of 975 isolates were collected, mainly from the Central Highlands of Mexico. In this study, the occurrence of F. graminearum sensu stricto (F. graminearum s.s.) was reported for the first time in Mexico. First identified in 2014, its occurrence showed an increasing trend over the years, accounting for 34.77% of the sampled isolates. F. boothii was the most frequent species, representing 54.46% of the isolates, though it exhibited a decreasing trend across time. In addition to these two species, this study identified eight F. meridionale isolates and 97 non-FGSC isolates. Sequence-Tagged Site (STS) and Kompetitive Allele-Specific PCR (KASP) markers were developed to effectively differentiate between F. graminearum s.s., F. boothii and F. meridionale. All three type B trichothecene chemotypes were identified among the F. graminearum s.s. isolates: 76.11% were of the 3-acetyldeoxynivalenol (3-ADON) chemotype, 23.60% were of the 15-acetyldeoxynivalenol (15-ADON) chemotype, and only one isolate belonged to the nivalenol (NIV) chemotype. The frequency of the 3-ADON chemotype increased over time. In vitro experiments revealed that this chemotype exhibited significantly higher DON productivity than the 15-ADON and NIV chemotypes, along with greater pathogenicity in greenhouse experiments. These findings highlight the importance of monitoring pathogen composition and chemotype prevalence changes for developing effective Fusarium management and resistance breeding strategies.