Turcicum leaf blight (TLB), is a common foliar disease of maize in Mexico that is caused by the fungal pathogen Exserohilum turcicum. The most effective management strategy against TLB is monogenic race-specific resistance. Among the 140 E. turcicum isolates from symptomatic leaves collected from maize fields in Mexico, 100 were obtained from tropical (Veracruz) and temperate areas (Estado de México) between 2010 and 2019, and 40 isolates were obtained from tropical (Sinaloa, Tamaulipas, Veracruz, and Chiapas), subtropical (Nayarit, Jalisco and Guanajuato) and temperate areas (Estado de Mexico, Hidalgo, and Puebla) collected in 2019. All the isolates caused TLB symptoms on the positive control (ht4) showing that they were all pathogenic. Six physiological races of E. turcicum (2, 3, 23, 3N, 23N, and 123N) were identified based on resistant or susceptible responses displayed by five maize differential genotypes (A619Ht1, A619Ht2, A619Ht3, B68HtN, and A619ht4). The most common was race 23 accounting for 68% of the isolates, followed by races 23N, 123N, 3, 2, and 3N at 15%, 8%, 6%, 2%, and 1%, respectively. Race 123N was able to infect the greatest number of maize differential genotypes used in the study. Race 123N was detected in Sinaloa and Estado de México. Race 3 was detected in Nayarit and Jalisco. Race 2 was detected in Jalisco, Estado de México and Veracruz, and race 3N was detected in Tamaulipas. Race 23 was equally dominant in the tropical, subtropical, and temperate regions, while race 123N was more common in the tropical environment and race 23N was more common in the tropical and temperate environments. There was no evidence for shifts in the races between 2010 and 2019.

Aflatoxins (AFs) and fumonisins (FUMs) are among the most prevalent and toxic mycotoxins affecting maize production globally. In Mexico, their co-occurrence poses a significant public health concern, as maize is not only a dietary staple but also predominantly grown and consumed at the household level. This review examines the multifactorial nature of AFs and FUMs contamination in Mexican maize systems, considering the roles of maize germplasm, agricultural practices, environmental conditions, and soil microbiota. Maize landraces, well-adapted to diverse agroecological zones, exhibit potential resistance to AFs contamination and should be prioritized in breeding programs. Sustainable agricultural practices and biocontrol strategies, including the use of atoxigenic Aspergillus flavus strains, are presented as promising interventions. Environmental factors and soil characteristics further influence fungal proliferation and mycotoxin biosynthesis. Advances in microbiome engineering, biological breeding approaches, and predictive modeling offer novel opportunities for prevention and control. The synergistic toxicity of AFs and FUMs significantly increases health risks, particularly for liver cancer, highlighting the urgency of integrated mitigation strategies. While Mexico has regulatory limits for AFs, the lack of legal thresholds for FUMs remains a critical gap in food safety legislation. This comprehensive review underscores the need for biomarker-based exposure assessments and coordinated national policies, alongside multidisciplinary strategies to reduce mycotoxin exposure and enhance food safety in maize systems.

Maize ear rot caused by Fusarium species reduces yield and compromises grain quality through mycotoxin contamination. During the 2023 and 2024 growing seasons, symptomatic maize ears with whitish to reddish fungal growth and partial kernel decay were collected from 14 representative commercial fields in the Bajío region (Guanajuato, Jalisco, and Michoacán, Mexico), which is a major maize-producing area with a history of ear rot disease. Ten to fifteen ears per field were randomly sampled, manually shelled, and pooled to create a composite sample. From each sample, 48 kernels (three replicates), without prior classification based on symptom expression, were surface disinfested in 1% sodium hypochlorite for 2 min, rinsed twice in sterile distilled water, and incubated in moist chambers at 25°C for 5 to 7 days. Colonies with Fusarium-like morphology that developed from the kernels were subcultured onto potato dextrose agar and purified by single-spore isolation (Leslie and Summerell 2006). Two morphologically distinct Fusarium colony types were consistently observed. One produced abundant white aerial mycelium that developed reddish to burgundy pigmentation; its macroconidia were hyaline, falcate, with four to seven septa, measuring 32.5–65.1 × 2–4 µm, and microconidia and chlamydospores were absent. The other produced white to pinkish aerial mycelium; its macroconidia were falcate with three to five septa, measuring 22–53.5 × 2.4–4.3 µm, with abundant unicellular microconidia in short chains and intercalary chlamydospores. Genomic DNA from representative isolates was used to amplify partial sequences of the translation elongation factor 1-α (TEF1-α) and RNA polymerase II subunit (RPB2) (O’Donnell et al. 2022). Sequences were assembled, aligned with reference datasets, and analyzed using maximum-likelihood phylogeny of concatenated TEF1-α and RPB2 under the GTR+G model with 1,000 bootstrap replicates using MEGA11 (Tamura et al. 2021). Phylogenetic analyses confirmed the morphological identification, showing that the first colony type corresponded to Fusarium boothii (a member of the Fusarium graminearum species complex, FGSC) and the second to Fusarium sudanense (a member of the Fusarium fujikuroi species complex, FFSC). Representative sequences were deposited in GenBank under accession numbers PX894867, PX894887, PX894860, and PX894880. Pathogenicity was evaluated under field conditions in 2025. A conidial suspension (5 × 10⁵ conidia ml⁻¹) from 7-day-old cultures was injected into maize ears 7 days after silking, while control ears received sterile distilled water. For each species, 10 ears per replicate were inoulated with three replicates. Symptoms appeared within 21 days, resembling those observed in naturally infected ears. The fungi were re-isolated from symptomatic kernels, and control ears remained asymptomatic. Morphological and molecular characteristics of the reisolated isolates matched the original cultures, fulfilling Koch’s postulates. Although F. boothii has been reported in Mexico as a causal agent of Fusarium head blight of wheat (Malihipour et al. 2012) and as a cause of maize ear rot in other regions of the world (Belizán et al. 2019), F. sudanense has been reported as a causal agent of seed rot and seedling blight in wheat (Larran et al. 2020). This is the first report of F. boothii and F. sudanense causing maize ear rot in Mexico.