Abstract
Mycological investigation of various foods (mainly cowpea, groundnut, maize, rice, sorghum) and agricultural soils from two states in north-central Nigeria (Nasarawa and Niger), was conducted in order to understand the role of filamentous fungi in food contamination and public health. A total of 839 fungal isolates were recovered from 84% of the 250 food and all 30 soil samples. Preliminary identifications were made, based on macro- and micromorphological characters. Representative strains (n = 121) were studied in detail using morphology and DNA sequencing, involving genera/species-specific markers, while extrolite profiles using LC-MS/MS were obtained for a selection of strains. The representative strains grouped in seven genera (Aspergillus, Fusarium, Macrophomina, Meyerozyma, Neocosmospora, Neotestudina and Phoma). Amongst the 21 species that were isolated during this study was one novel species belonging to the Fusarium fujikuroi species complex, F. madaensesp. nov., obtained from groundnut and sorghum in Nasarawa state. The examined strains produced diverse extrolites, including several uncommon compounds: averantinmethylether in A. aflatoxiformans; aspergillimide in A. flavus; heptelidic acid in A. austwickii; desoxypaxillin, kotanin A and paspalitrems (A and B) in A. aflatoxiformans, A. austwickii and A. cerealis; aurasperon C, dimethylsulochrin, fellutanine A, methylorsellinic acid, nigragillin and pyrophen in A. brunneoviolaceus; cyclosporins (A, B, C and H) in A. niger; methylorsellinic acid, pyrophen and secalonic acid in A. piperis; aspulvinone E, fonsecin, kojic acid, kotanin A, malformin C, pyranonigrin and pyrophen in A. vadensis; and all compounds in F. madaense sp. nov., Meyerozyma, Neocosmospora and Neotestudina. This study provides snapshot data for prediction of food contamination and fungal biodiversity exploitation.
Highlights
Fungi are ubiquitous and diverse, inhabiting various environments including agricultural soils and the crops grown on them (Stajich et al 2009)
A similar fungal load found in soil samples in the present study was previously reported for 55 soil samples collected from maize fields across three agro-ecological zones of Nigeria (Donner et al 2009)
To the best of our knowledge, we present the first report of Neotestudina from Nigerian soil
Summary
Fungi are ubiquitous and diverse, inhabiting various environments including agricultural soils and the crops grown on them (Stajich et al 2009). Fungi in soil can contaminate, invade and colonise crops on the field during pre-harvest stages and can remain present during the post-harvest processing stages. Fungal contamination and colonisation of crops could directly lead to pre- and post-harvest food losses, mycotoxin contamination and indirectly to public health risks from consumption of mycotoxincontaminated foods (Avery et al 2019). Soil could serve as a reservoir for pathogenic fungi, constituting public health hazards to farmers who spend much of their time on farms and have direct contact with agricultural soils. Beneficial fungi, including biological control strains and species of industrial relevance, are present in agricultural soils, waiting to be explored (Donner et al 2009, Bautista-Rosales et al 2013, Bandyopadhyay et al 2016)
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