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A sample of 140 Fusarium graminearum isolates from Rio Grande do Sul, Brazil, representing three populations at least 150 km from one another, were examined for trichothecene genotype based on PCR amplification of portions of the Tri3 and Tri12 genes and a species-specific (Fg16F ⁄ R) primer pair. Genetic diversity was assessed in a sample of 103 F. graminearum lineage 7 (F. graminearum sensu stricto) isolates using amplified fragment length polymorphism (AFLP) markers. The 15-ADON genotype was dominant, followed by the NIV genotype (2-18% prevalence), across all three populations. All NIV-type isolates were in lineage 2 (F. meridionale) and all 15-ADON-type isolates were in lineage 7. Isolates with the same haplotype were rare and genotypic diversity was uniformly high ( ‡98% of the count), suggesting that recombination has played a significant role. The number of migrants (N m ) was estimated between 5 and 6 across all loci and all populations, but the high frequency of private alleles (up to 30%) suggests a historical, rather than contemporary, gene flow. Regarding linkage disequilibrium, 0AE8, 1AE5 and 2AE2% of the locus pairs from the three populations were in disequilibrium, which is lower than values reported in other locations. Thus, Brazilian populations differ from those found in Europe, North America and most of Asia in the presence of a significant frequency (7AE8%) of isolates of the NIV genotype in lineage 2.

Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight of wheat. The authors used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of two G. zeae populations from commercial wheat fields. The working hypothesis was that sufficient genetic exchange occurs between local populations to prevent significant partitioning of allelic variation. We analysed 216 AFLP loci for 113 isolates collected during the 2002 harvest season. All strains had AFLP profiles typical of G. zeae lineage 7. Both populations were genotypically diverse but genetically similar and potentially part of a larger, randomly mating population, with significant genetic exchange probably occurring between the two subpopulations. Linkage disequilibrium was low, but higher than reported for many other populations of G. zeae, and about 20% of the alleles detected were specific to one of the two subpopulations - results consistent with limited gene exchange between the two subpopulations. This study extends previous work with populations of G. zeae to include those found in Argentina, one of the world's largest wheat growing countries.

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Sumíková T., Gabrielová L., Kučera L., Žabka M., Chrpová J. (2013): Mycotoxin production, chemo-types and diversity of Czech Fusarium graminearum isolates on wheat. Czech J. Food Sci., 31: 407-412. Fusarium head blight (FHB) is a serious cereal disease in the Czech Republic. The most important pathogen associated with FBH is Fusarium graminearum, which can produce trichothecenes, mainly deoxynivalenol (DON) and its derivates. A set of 103 F. graminearum isolates were isolated from naturally infected wheat ears collected from 20 localities (25 ears from one locality) within the Czech Republic, in the year 2004. The ears were evaluated for DON content by ELISA. Maximum detected value was 30.7 mg/kg. A group of PCR assays targeting the segments of the Tri7, Tri13 and Tri3 genes were used to determine the chemotypes of F. graminearum isolates. All the isolates belonged to DON producing chemotype. Further discrimination revealed that almost all (99.03%) isolates belonged to 15-ADON chemotype, and only one (0.97%) isolate belonged to 3-ADON chemotype. The genetic variability of the isolates was assessed from their AFLP fingerprints. The populations were highly heterogeneous both within and between locations, and no clear evidence for the association between AFLP profile and geographic origin was found out.

Soybean (Glycine max L.), the main source of protein throughout the world, is used both as a food and a feedstuff. Currently, limited information about the occurrence of Fusarium species and mycotoxins in soybean grain and by-products is available. The aims of the present study were: (1) to identify toxigenic Fusarium species associated with soybean during crop reproductive stages; (2) to determine the occurrence of deoxynivalenol (DON) and nivalenol (NIV) in soybean seeds; (3) to determine the genotype and chemotype of selected Fg complex strains using molecular and chemical analysis, respectively; and (4) to characterize the strains using AFLP(s) markers. One soybean field located at Córdoba Province, Argentina, was monitored and samples of soybean tissue were harvested at three reproductive stages: flowering (R2), full seed (R6) and full maturity (R8). A total of 389 Fusarium strains F. equiseti (40%) was the most frequently species recovered followed by F. semitectum (27%) and F. graminearum (Fg) (11%). From the 40 soybean samples analysed, only two presented detectable DON levels. Based on DON occurrence on soybean seeds at ripening stages, the toxigenic ability of Fg complex strains isolated from soybean seeds, pods and flowers were analysed. The trichothecene genotype was determined by a multiplex PCR using primers based on Tri3, Tri5 and Tri7 toxin genes and then the chemotype was verified by chemical analysis. Most Fg complex strains showed 15-ADON genotype and five strains presented a DON/NIV; these also produced both toxins under in vitro culture. Neither the NIV nor the 3-ADON genotypes were detected among the members of the population evaluated. All the 15-ADON genotype strains were characterized as F. graminearum sensu stricto (lineage 7), while the strains presented a DON/NIV genotype were characterized as F. meridionale (lineage 2). The present study contributes new information on the occurrence of Fusarium species and trichothecenes toxins on soybean at the pre-harvest stages. Also, this is the first report on the chemotype, genotype and lineages among Fg complex isolated from soybean.

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