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<p>Cowpea (<i>Vigna unguiculata</i> (L.) Walp) is a valuable legume crop for many people in tropical and subtropical countries worldwide and serves as an inexpensive source of proteins for humans and animals. Although it is not considered a major commercial crop in South Africa, cowpea plays an important part in subsistence and smallholder farming systems. Cowpea seeds when stored under unfavourable conditions are susceptible to fungal infestation and subsequent contamination of harmful mycotoxins. There is limited information regarding the natural occurrence of mycotoxigenic fungi and mycotoxin contamination of cowpea seed in South Africa. Therefore, this study was conducted to investigate which fungi and mycotoxins are naturally present in cowpea seed, and to determine whether there is a potential health risk for the consumers. Forty-eight seed samples were collected from South African subsistence and smallholder farmers from the main growing areas. Surface sterilised and non-sterilised seeds were plated onto potato dextrose agar (PDA), fungi were isolated and identified morphologically, and molecularly using Sanger sequencing and phylogenetic analyses. Mycotoxins were analysed using ultra-performance liquid chromatography (UPLC) – electrospray ionization (ESI) tandem mass spectrometry (MS/MS). In total, sixteen different fungal genera were identified at various incidence levels. All samples showed high incidence of fungi (up to 70%), with <i>Fusarium</i> spp. being the most prominent. No mycotoxins were detected in the seed samples. Selected fungal isolates did however produce mycotoxins on maize cultures, including fumonisin B<sub>1</sub> (0.014—1092,402&#xa0;mg/kg), B<sub>2</sub> (0,030–247,906&#xa0;mg/kg) and B<sub>3</sub> (0,026—54,010&#xa0;mg/kg), ochratoxin A (0,053 – 0,042&#xa0;mg/kg), zearalenone (0,036—0,277&#xa0;mg/kg), deoxynivalenol (0.190—0.658&#xa0;mg/kg) and nivalenol (4.510 – 25,099&#xa0;mg/kg). This study confirmed a high incidence of potentially harmful mycotoxigenic fungi isolated from stored cowpea seed samples across the cowpea-producing areas of South Africa. Mycotoxin production by these fungi could pose a severe health risk to both humans and animals since cowpea is produced as a nutritious food source.</p>

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Mycoflora and mycotoxins associated with stored cowpea (Vigna unguiculata L. Walp) seeds from smallholder farmers in South Africa

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  • 发表日期：

    2025年4月10日

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  • Johannes Jacobus Francois Viljoen,
  • Mariette Truter,
  • Quenton Kritzinger

摘要

Cowpea (Vigna unguiculata (L.) Walp) is a valuable legume crop for many people in tropical and subtropical countries worldwide and serves as an inexpensive source of proteins for humans and animals. Although it is not considered a major commercial crop in South Africa, cowpea plays an important part in subsistence and smallholder farming systems. Cowpea seeds when stored under unfavourable conditions are susceptible to fungal infestation and subsequent contamination of harmful mycotoxins. There is limited information regarding the natural occurrence of mycotoxigenic fungi and mycotoxin contamination of cowpea seed in South Africa. Therefore, this study was conducted to investigate which fungi and mycotoxins are naturally present in cowpea seed, and to determine whether there is a potential health risk for the consumers. Forty-eight seed samples were collected from South African subsistence and smallholder farmers from the main growing areas. Surface sterilised and non-sterilised seeds were plated onto potato dextrose agar (PDA), fungi were isolated and identified morphologically, and molecularly using Sanger sequencing and phylogenetic analyses. Mycotoxins were analysed using ultra-performance liquid chromatography (UPLC) – electrospray ionization (ESI) tandem mass spectrometry (MS/MS). In total, sixteen different fungal genera were identified at various incidence levels. All samples showed high incidence of fungi (up to 70%), with Fusarium spp. being the most prominent. No mycotoxins were detected in the seed samples. Selected fungal isolates did however produce mycotoxins on maize cultures, including fumonisin B1 (0.014—1092,402 mg/kg), B2 (0,030–247,906 mg/kg) and B3 (0,026—54,010 mg/kg), ochratoxin A (0,053 – 0,042 mg/kg), zearalenone (0,036—0,277 mg/kg), deoxynivalenol (0.190—0.658 mg/kg) and nivalenol (4.510 – 25,099 mg/kg). This study confirmed a high incidence of potentially harmful mycotoxigenic fungi isolated from stored cowpea seed samples across the cowpea-producing areas of South Africa. Mycotoxin production by these fungi could pose a severe health risk to both humans and animals since cowpea is produced as a nutritious food source.