Héctor E. Villaseñor-Mir

Regional differences in the composition of Fusarium Head Blight pathogens and mycotoxins associated with wheat in Mexico

Fusarium Head Blight (FHB) is a destructive disease of small grain cereals and a major food safety concern. Epidemics result in substantial yield losses, reduction in crop quality, and contamination of grains with trichothecenes and other mycotoxins. A number of different fusaria can cause FHB, and there are significant regional differences in the occurrence and prevalence of FHB pathogen species and their associated mycotoxins. Information on FHB pathogen and mycotoxin diversity in Mexico has been extremely limited, but is needed to improve disease and mycotoxin control efforts. To address this, we used a combination of DNA sequence-based methods and in-vitro toxin analyses to characterize FHB isolates collected from symptomatic wheat in Mexico during the 2013 and 2014 growing seasons. Among 116 Fusarium isolates, we identified five species complexes including nine named Fusarium species and 30 isolates representing unnamed or potentially novel species. Significant regional differences (P < 0.001) in pathogen composition were observed, with F. boothii accounting for >90% of isolates from the Mixteca region in southern Mexico, whereas F. avenaceum and related members of the F. tricinctum species complex (FTSC) accounted for nearly 75% of isolates from the Highlands region in Central Mexico. F. graminearum, which is the dominant FHB pathogen in other parts of North America, was not present among the isolates from Mexico. F. boothii isolates had the 15-acetyldeoxynivalenol toxin type, and some of the minor FHB species produced trichothecenes, such as nivalenol, T-2 toxin and diacetoxyscirpenol. None of the FTSC isolates tested was able to produce trichothecenes, but many produced chlamydosporol and enniatin B.

CARACTERIZACIÓN DE ESPECIES DEFusariumCAUSANTES DE PUDRICIÓN DE RAÍZ DEL TRIGO EN EL BAJÍO, MÉXICO

The objectives of this study were to identify Fusarium species causing root rot in wheat produced in the Bajío of Mexico, and to determine the response of 28 wheat varieties to this disease. Fusarium spp. isolates were obtained from samples with root rot symptoms in 2014 and 2015. The fungal isolates were identified by morphological characterization and sequence analysis of ITS and TEF-1α, and also using specific primers for the detection of Fusarium species. Pathogenicity of a representative isolate of each Fusarium species was verified by immersion of seeds of 28 wheat varieties in a conidial suspension. The results of the morphological characterization, sequence analysis, and pathogenicity Recibido: 12 agosto 2016. Aceptado: 28 Febrero 2017. ISSN 0719-3882 print ISSN 0719-3890 online