The level of mycotic and mycotoxigenic Fusaria in traditional morogo and the agro-environment of Dikgale Demographic Surveillance Site (DDSS)
Mogakabe, Ditselatsela Elijah
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Ubiquitous in agro-environments, Fusarium species infect and damage economically important crops and contaminate food commodities with harmful secondary metabolites called mycotoxins. In addition, human infection by pathogenic Fusarium strains has now emerged as a major problem particularly among individuals with suppressed immunity. Trichothecenes, deoxynivalenol, nivalenol, rnoniliforme and fumonisins are potent toxins produced by Fusorium species including F. poae, F. nygami, F. oxysporum, F. proilferatum and F. verticillioides. The last three, together with F. solani and F. chlamydosporum are presently recognised as major role players in the occurrence of fusarioses in individuals with compromised immunity. In subsistence situations in rural areas of South Africa, a variety of traditional leafy vegetables, collectively known as morogo, supplement maize-based staple diets with minerals and vitamins. The utilisations of these traditional vegetables are generally based on indigenous knowledge pertaining to production and processing. Morogo plants are not natural hosts to mycotoxigenic and mycotic Fusarium species that are mainly associated with pathogeneses of grain crops such as maize. However, morogo growing in close proximity of maize in typical subsistence agricultural situations might be at risk of Fusarium contamination from maize. The study was conducted in the Dikgale Demographic Surveillance Site (DDSS), a rural area in the Limpopo Province characterised by the production of maize and different types of traditional morogo for household subsistence. HIVIAIDS is prevalent in the Limpopo Province. Chronic dietary exposure to Fusarium toxins and disseminated fusarioses might enhance disease outcomes associated with AIDS in affected individuals, thus adding to the burden of disease in DDSS communities. The aim of the study was to investigate the occurrence of mycotic and mycotoxigenic Fusarium species in traditional morogo and ago-environments in DDSS. Questionnaires were employed to obtain relevant information and indigenous knowledge from communities of Sefateng. Madiga, Mantheding and Moduane related to the utilisation of raditional morogo. At each village thepe (amaranth) and lerotho (African cabbage) were sampled on two occasions, namely before maize planting (M-) and when maize was fully grown (M+). Maize, soil and air were sampled at the same time. Botanical species identification was carried out on specimens of lerotho and thepe from each village. Lerotho. thepe, maize, soil and air samples were subjected to mycological analysis to determine the average fungal levels and Fusarium species that occurred. Samples of fresh and traditionally sun-dried samples of thepe and lerotho were analysed by HPLC for fumonisins. Average fungal plate counts of morogo from all four villages were notably higher in lerotho compared to thepe. Lerotho sampled from M- fields of Madiga, Mantheding and Moduane exhibited higher average fungal levels than those from the M+ fields. However, in lerotho sampled from the M+ field of Sefateng average fungal levels were significantly higher than that of the M- field. Fungal levels in maize growing close to morogo were lowest in Sefateng and highest in Moduane. The highest fungal counts in soil were reported for Sefateng's M- field and the lowest for Sefateng M+ field. Fungal levels were high in air samples of M+ fields of all four villages and the lowest in M- field of Sefateng. The majority Fusarium isolates retrieved from morogo and environmental samples belonged to known mycotoxigenic and/or mycotic species, though predominant species and levels thereof varied in samples from M- and M+ fields of the four villages. Fusarium levels in thepe from both M- and M+ fields were shown to be lower as in lerotho. In samples of the Sefateng M- field, F. poae occurred predominantly in lerotho, thepe, soil as well as air, while F. subglutinans was the predominant species in lerotho and air samples of Mantheding. In Sefateng samples from M+ field, F. chlamydosporum predominated among isolates retrieved from lerotho, F. prolifiratum and F. gramenearum among those from maize and F. solani among those from soil and air. F. proliferatum dominated among isolates from lerotho, maize, soil and air of M+ sites of Madiga and F. chlamydosporum in soil and air samples of Mantheding. HPLC analysis detected fumonisin B1 in traditionally sun-dried as well as fresh samples of lerorho as well as thepe. The occurrence of mycotoxigenic and rnycotic Fusarium species in traditional morogo and agro-environments might be an aggravating health risk factor for DDSS communities.
- ETD@PUK