Abstract
We compared two well-established methods, fungal isolation followed by conventional PCR and DNA analysis by quantitative PCR (qPCR), to define trichothecene genotypes in Brazilian wheat grains from different locations. For this purpose, after fungal isolation from 75 wheat samples, 100 isolates of the Fusarium graminearum species complex (FGSC) were genotyped by PCR to establish their trichothecene profile. For profiling by qPCR, DNA was extracted from the wheat samples and analyzed. The methods provided similar and divergent results. The FGSC isolates were classified as NIV (55%), 15-ADON (43%), and 3-ADON (2%). Analysis by qPCR showed 100% contamination with 15-ADON strains in all wheat samples, 80% contamination with the NIV genotype, and only 33.3% contamination with 3-ADON strains. Further analysis revealed that 96% of all quantified DNA was attributed to the 15-ADON profile, while 3.4% was attributed to NIV and only 0.06% to 3-ADON. A positive correlation was observed between 15-ADON genotype DNA concentration and deoxynivalenol (DON) content in the wheat samples. The high frequency of fungi, DNA levels and positive correlation with DON strongly indicate that 15-ADON producers are the main trichothecene genotype in Brazilian wheat grains. Surprisingly, although many isolates (55%) carried the NIV genotype and this genotype was identified in 80% of the wheat samples, only 3.4% of fungal DNA was in fact from NIV producers. Although, our findings showed that each method provided a different perspective about the trichothecene profile, DNA analysis by qPCR gave us new insight about fungal contamination levels in Brazilian wheat grains. Nevertheless, both techniques should be used to obtain more robust results.
Highlights
The continuous increase in wheat production in Brazil (USDA, 2014) and recent mycotoxin regulations (ANVISA, 2011) indicate the urgent need for more studies about fungal diversity and mycotoxin profiles found in these grains to ensure a good-quality and safe product for human and animal consumption
Mycobiota analysis of the wheat samples revealed that the 15-ADON genotype was attributed to Fusarium graminearum sensu stricto (s.s.), NIV to F. meridionale, and NIV or 3-ADON to F. cortaderiae and F. austroamericanum (Tralamazza et al, 2016), all belonging to the Fusarium graminearum species complex (FGSC) group
Two methods were used to investigate the trichothecene genotype profile of Brazilian wheat grains. Both techniques demonstrated that 3-ADON is not a relevant genotype in Brazilian wheat grains
Summary
The continuous increase in wheat production in Brazil (USDA, 2014) and recent mycotoxin regulations (ANVISA, 2011) indicate the urgent need for more studies about fungal diversity and mycotoxin profiles found in these grains to ensure a good-quality and safe product for human and animal consumption. Type B trichothecenes synthesized by FGSC vary worldwide and their profile is normally divided into three categories: (1) nivalenol (NIV) and its acetylated form (4-ANIV); (2) deoxynivalenol (DON) and 15-acetyldeoxynivalenol (15ADON); (3) DON and 3-acetyldeoxynivalenol (3-ADON) (Ward et al, 2002; Desjardins, 2006). These toxins are included in the same group, they may differ in terms of aggressiveness and toxicity (Lee et al, 2009; Puri and Zhong, 2010; Umpiérrez-Failache et al, 2013). In view of the possibility of different profiles, it is important to characterize potential mycotoxins in cereals and to analyze shifts in the toxigenic profile of fungal populations
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