Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from groundnuts in selected agroecological zones of Uganda
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
BMC microbiology
Abstract
Background
Aspergillus is the main fungal genus causing pre- and post-harvest contamination of
groundnuts. Aspergillus flavus belongs to section Flavi, a group consisting of both the aflatoxigenic species
(A. flavus, A. parasiticus and A. nomius) and non-aflatoxigenic species (A. oryzae, A. sojae and A. tamarii).
Aflatoxins are food-borne toxic secondary metabolites produced by Aspergillus species, causing hepatic
carcinoma and stunting in children and are the most toxic carcinogenic mycotoxins ever identified. Despite
the well-known public health problems associated with aflatoxicosis in Uganda, information about the
genetic diversity of the main aflatoxin causing fungus, Aspergillus flavus in this country is still limited.
Results
A cross-sectional survey was therefore carried out in three main groundnut-growing agro-ecological
zones (AEZs) of Uganda; West Nile farming system, Lake Kyoga basin mixed farming system and Lake
Victoria basin farming system. This was to assess the genetic diversity of A. flavus and to establish the
contamination rates of groundnuts with Aspergillus species at pre- and post-harvest stages. Out of the 213
A. flavus isolates identified in this study, 96 representative isolates were fingerprinted using 16
insertion/deletion microsatellite markers. Data from fingerprinting were analyzed through Neighbor Joining
while polymorphism was determined using Arlequin v 3.5. The pre- and post-harvest contamination rates
were; 2.5% and 50.0% (West Nile farming system), 55.0% and 35.0% (Lake Kyoga basin mixed farming
system) and 32.5% and 32.5% (Lake Victoria basin farming system) respectively. The Chi-square test
showed no significant differences between pre- and post-harvest contamination rates among AEZs (p =
0.199). Only 67 out of 96 isolates produced suitable allele scores for genotypic analysis. Analysis of genetic
diversity showed higher variation within populations than among populations. Two major clusters
(aflatoxigenic and non-aflatoxigenic isolates) were identified as colonizing groundnuts at pre- and postharvest
stages.
Conclusions
These findings provide a first insight on the existence of non-aflatoxigenic
strains of A. flavus in Uganda. These strains are potential candidates for developing local Aspergillus biocontrol
agent.
Description
Keywords
Mycotoxins, Secondary metabolites, Aspergillus species, Agro-ecological zone
Citation
Acur, A., Arias, RS, Odongo, S., Tuhaise, S., Ssekandi, J., Adriko, J., ... & Kiggundu, A. (2020). Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from selected groundnut growing agro-ecological zones of Uganda. BMC microbiology , 20 (1), 1-12. https://doi.org/10.21203/rs.2.13266/v1