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Members of the Fusarium graminearum species complex (Fg complex) are the causal agents of ear rot in maize and Fusarium head blight of wheat and other small grain cereals. The potential of these pathogens to contaminate cereals with trichothecene mycotoxins is a health risk for both humans and animals. A survey of ear rot isolates from maize collected in northwest Argentina recovered 66 isolates belonging to the Fg complex. A multilocus genotyping (MLGT) assay for determination of Fg complex species and trichothecene chemotypes was used to identify 56 of these isolates as F. meridionale and 10 isolates as F. boothii. F. meridionale was fixed for the nivalenol (NIV) chemotype, and all of the F. boothii isolates had the 15-acetyldeoxynivalenol (15ADON) chemotype. The results of genetic diversity analysis based on nine variable number tandem repeat (VNTR) loci supported the hypothesis of genetic isolation between F. meridionale and F. boothii, and provided little evidence of geographic substructure among populations of the dominant pathogen species, F. meridionale. This is the first study to indicate that F. meridionale and F. boothii may play a substantial role in the infection and trichothecene contamination of maize in Argentina. In addition, dominance of the NIV chemotype among Fg complex isolates from Argentina is unprecedented, and of significant concern to food safety and animal production., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Fusarium species are worldwide causal agents of ear rot in cereals. Their toxigenic potential is a health risk for both humans and animals. In Argentina, most identification of these fungi has been based on morphological and cross-fertility criteria which are time consuming and require considerable expertise in Fusarium taxonomy and physiology. DNA based approaches have been reported as rapid, sensitive and specific alternatives to identify the main fumonisin and trichothecene-producing Fusarium species. In this work, we used PCR assays and the partial sequence of TEF1-alpha gene (Translation Elongation Factor-1 alpha) to identify the fumonisin and trichothecene-producing species in Fusarium isolates from diverse regions of Argentina. The relative efficiency and reliability of those methods to improve mycotoxin risk prediction in this country were also assessed. Species-specific PCR assays were targeted toward multicopy IGS (Intergenic Spacer of rDNA units) and on the toxin biosynthetic genes FUM1 (fumonisins) and TRI13 and TRI7 genes (trichothecenes). PCR assays based on FUM1 gene and IGS sequences allowed detection and discrimination of the fumonisin producers Fusarium proliferatum and Fusarium verticillioides. Molecular identification of nonfumonisin producers from Gibberella fujikuroi species complex was possible after determination of TEF1-alplha gene sequences, which indicated the presence of Fusarium subglutinans, Fusarium andiyazi and Fusarium thapsinum. TEF-1 alpha gene sequences also allowed discrimination of the different species of the Fusarium graminearum complex (F. graminearum sensu lato) as F. graminearum sensu stricto, Fusarium meridionale and Fusarium boothii. The last two species belonged to NIV chemotype and were detected for the first time in the subtropical region of Argentina while F. graminearum sensu stricto was DON producer only, which was also confirmed by specific PCR assays based on TRI137/TRI7 genes. Our results indicated that the PCR assays evaluated in this work are reliable diagnostic tools to detect the main toxigenic Fusarium species associated to cereal grains in Argentina. An extensive epidemiological survey based on the approach presented in this work is currently in progress to know the mycotoxigenic hazard of Fusarium species in cereal grains from the subtropical region of Argentina., (Copyright © 2009 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.)