Abstract
There is little knowledge of the microbial diversity, mycotoxins and associated secondary metabolites in GM maize and isogenic non-GM cultivars (cvs). This study has quantified the microbial populations and dominant fungal genera in 6 cvs of each type representative of herbicide, pesticide or stacked resistance to both. The predominant mycotoxins and targeted metabolomics profiles were also compared between the two sets of cvs. This showed that the overall fungal populations were 8.8 CFUs g−1 maize. The dominant genera, isolated from maize samples, whether surface-sterilised or not, in all maize cvs were Fusarium, followed by Penicillium, Aspergillus and occasionally Cladosporium and Alternaria. The analysis of the targeted metabolomics showed that approx. 29 different metabolites were detected. These were dominated by fumonisins and minor Penicillium spp. metabolites (questiomycin A and rugulovasine A). Interestingly, the range and number of mycotoxins present in the GM cvs were significantly lower than in the non-GM maize samples. This suggests that while the fungal diversity of the two types of maize appeared to be very similar, the major contaminant mycotoxins and range of toxic secondary metabolites were much lower in the GM cvs.
Highlights
In many parts of the world, maize production has become dominated by GM cultivars which have replaced conventional ones, especially for improving herbicide and pesticide resistance
Enumeration of the fungal populations isolated from the GM and non-GM maize samples
There was no significant difference in the populations (CFUs) between the samples at the 5% significance level on either Malt Extract Agar (MEA) or Dichloran-Glycerol 18% agar (DG18) media
Summary
In many parts of the world, maize production has become dominated by GM cultivars (cvs) which have replaced conventional ones, especially for improving herbicide and pesticide resistance. Fungal pathogens of maize are responsible for significant economic losses in terms of yield and nutritional quality, especially during the critical silking period up to harvest. The major foliar pathogens include rusts, leaf spots, anthracnose, mildews. In Brazil, maize represents an important economic and social product in both family farming and agribusiness (Vidal et al 2015). Soybean production is the highest, followed by maize. Brazil has been a leader in the development of different biotechnology-modified traits, including 39 for maize (ISAAA 2017). Maize is cultivated in the summer and winter months in Mycotoxin Res (2021) 37:39–48
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