Susceptibility of locally cultivated groundnut (Arachis hypogaea) varieties to aflatoxin accumulation in Homa Bay County, Kenya

Abstract

Groundnut is one of the staple foods in many parts of the world. Due to its high nutrient content, the nuts are liable to colonization by aflatoxigenic fungi and subsequent aflatoxin accumulation. This study was aimed at determining susceptibility of locally grown groundnut varieties to Aspergillus flavus in Homa Bay County, Western Kenya. A pretested questionnaire was used to survey agronomic practices on groundnut cultivation in 75 randomly selected households in the study site. From each household farm, 100 g soil samples and 500 g of groundnuts were collected at harvest and A. flavus isolated on Modified Rose-Bengal Agar and identified. Aflatoxin was then extracted from each of the groundnut samples and quantified using direct competitive enzyme linked immunosorbent assay (ELISA). Red Valencia was the most cultivated among the 8 varieties identified. Farmers (66%) obtained the planting seeds from the local market and most (92%) did not use fertilizers with majority (94%) having no knowledge of aflatoxins. There was no significant inter-variety difference in aflatoxin accumulation (p=0.744, F=0.581, Df=6, 61). A highly significant association (t = 2.652; P = 0.010) was found between storage state of the groundnuts and aflatoxin levels, with 94% of the samples stored unshelled having aflatoxin levels below 10 ppb. Overall, only 6.7% of kernels sampled from all the divisions did not meet the EC aflatoxin limit of ≤4 ppb while 4% did not meet the KEBS limit of ≤10 ppb. Though the agronomic practices were poor, aflatoxin levels were predominantly low in the region suggesting that the aflatoxin accumulation is likely influenced by agro-ecological zoning as other studies have also been indicated.

Six Main Contributing Factors to High Levels of Mycotoxin Contamination in African Foods

“…In addition to these traditional storage facilities, grain protectants, such as Syzigum aromaticum plant and dried neem leaf powder with antifungal activities, among others, are added during storage [ 100 ]. Stored unshelled peanuts were found with reduced levels of aflatoxin contamination compared with stored shelled peanuts [ 101 ].…”

The aflatoxin situation in Africa : Systematic literature review

“…0.70-1.23 µg AFB1/ kg versus 1.30-1.97 µg/kg, respectively (Taye et al, 2018). Boaz et al (2017) surveyed West-Kenyan groundnut farmers for their agronomic practices and awareness of aflatoxin issues. They also checked for possible correlations with aflatoxin residues in harvested and stored groundnut samples, as well as for aflatoxigenic fungi in these samples and the farm soil.…”

“…In addition, if groundnuts were grown in rotation with maize, the population of moulds capable of forming aflatoxin was high. This may relate to the susceptibility of maize to infection by such moulds as well (Boaz et al, 2017). Whilst aflatoxin contamination was not particularly high, awareness of aflatoxin issues and mitigation turned out to be low (Boaz al., 2017).…”

Aflatoxigenic Aspergillus Modulates Aflatoxin-B1 Levels through an Antioxidative Mechanism

“…The aflD is a structural gene responsible for the early conversion of AF precursor molecules in the aflatoxin biosynthetic pathway [38,39] and is regulated by the regulatory genes aflR [40][41][42][43] and aflS. To enhance the understanding of the potential role of AF production and its utilisation in Flavi, two related questions need to be answered: (1) is AF degraded by atoxigenic Flavi as part of oxidative stress alleviation, and ( 2) is AF also degraded by aflatoxin-producing Flavi (toxigenic) as part of the mechanism of oxidative stress alleviation?…”

“…Aflatoxins (AFs) are a group of secondary metabolites produced by Aspergillus section Flavi ( Flavi , for short) members such as A. parasiticus and A. flavus . The group of fungi infects important cereals such as maize and groundnuts [ 1 , 2 , 3 , 4 , 5 , 6 ], resulting in crop AF contamination. Of the known AFs produced by Flavi , AF-B1 (B1) is a highly mutagenic compound and is the most carcinogenic [ 7 , 8 , 9 ].…”