Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from selected groundnut growing agro-ecological zones of Uganda

Abstract

Background: Groundnut pre-and post-harvest contamination is commonly caused by fungi from the Genus Aspergillus. Aspergillus flavus is the most important of these fungi. It belongs to section Flavi; a group consisting of aflatoxigenic (A. flavus, A. parasiticus and A. nomius) and non-aflatoxigenic (A. oryzae, A. sojae and A. tamarii) fungi. Aflatoxins are food-borne toxic secondary metabolites of Aspergillus species associated with severe hepatic carcinoma and children stuntedness. Despite the well-known public health significance of aflatoxicosis, there is a paucity of information about the prevalence, genetic diversity and population structure of A. flavus in different groundnut growing agroecological zones of Uganda. This cross-sectional study was therefore conducted to fill this knowledge gap. Results: The overall pre-and post-harvest groundnut contamination rates with A. flavus were 30.0 and 39.2% respectively. Pre-and post-harvest groundnut contamination rates with A. flavus across AEZs were; 2.5 and 50.0%; (West Nile), 55.0 and 35.0% (Lake Kyoga Basin) and 32.5 and 32.5% (Lake Victoria Basin) respectively. There was no significant difference (χ 2 = 2, p = 0.157) in overall pre-and post-harvest groundnut contamination rates with A. flavus and similarly no significant difference (χ 2 = 6, p = 0.199) was observed in the pre-and post-harvest contamination of groundnut with A. flavus across the three AEZs. The LKB had the highest incidence of aflatoxin-producing Aspergillus isolates while WN had no single Aspergillus isolate with aflatoxin-producing potential. Aspergillus isolates from the pre-harvest groundnut samples had insignificantly higher incidence of aflatoxin production (χ 2 = 2.667, p = 0.264) than those from the post-harvest groundnut samples. Overall, A. flavus isolates exhibited moderate level (92%, p = 0.02) of genetic diversity across the three AEZs and low level (8%, p = 0.05) of genetic diversity within the individual AEZs. There was a weak positive correlation (r = 0.1241, p = 0.045) between genetic distance and geographic distance among A. flavus populations in the LKB, suggesting that genetic differentiation in the LKB population might be associated to geographic distance. A very weak positive correlation existed between genetic variation and geographic location in the entire study area (r = 0.01, p = 0.471), LVB farming system (r = 0.0141, p = 0.412) and WN farming system (r = 0.02, p = 0.478). Hierarchical clustering using the unweighted pair group method with arithmetic means (UPGMA) revealed two main clusters of genetically similar A. flavus isolates.

Distribution, Genetic Diversity and Biocontrol of Aflatoxigenic Aspergillus flavus in Serbian Maize Fields

“…Generated genetic profiles of the aflatoxin biosynthesis gene cluster indicated intraspecies variability between the aflatoxigenic strains, which could be classified into four groups. Genetic diversity among A. flavus strains isolated from different localities could be explained by the difference in cropping practice employed in a certain field [48]. Additional reasons are gene flow as a result of human activities as well as different competition strategies of A. flavus strains depending on the environmental conditions [48].…”

“…Genetic diversity among A. flavus strains isolated from different localities could be explained by the difference in cropping practice employed in a certain field [48]. Additional reasons are gene flow as a result of human activities as well as different competition strategies of A. flavus strains depending on the environmental conditions [48].…”

Negligible Levels of Mycotoxin Contamination in Durum Wheat and Groundnuts from Non-Intensive Rainfed Production Systems

“…Acur et al [49] conducted a study on genetic diversity of aflatoxin-producing Aspergillus flavus in groundnut from three different agroecological zones in Uganda. Sixtyseven A. flavus isolates were identified, and subsequently characterized for the presence of aflatoxin biosynthesis gene cluster.…”

Toxigenic cosmopolitan micromycetes of the genus Aspergillus: new facts of recent decades

“…У A. flavus была подтверждена связь биосинтеза афлатоксинов и циклопиазоновой кислоты и метаболических путей, определяющих формирование склероциев [24]. Выяснилось, что разная экспрессия генов биосинтеза микотоксинов приводит к особенностям контаминации не только в определенных агроэкосистемах [13,25,26], но и в объектах. Так, у A. flavus, развивающегося в кукурузном зерне, активированы гены биосинтеза афлатоксинов и циклопиазоновой кислоты, а гены биосинтеза афлатрема подавлены [27].…”