Maize Aspergillus section Flavi isolate diversity may be distinct from that of soil and subsequently the source of aflatoxin contamination

AbstractAspergillus sectionFlavi (Flavi) is a diverse group of fungal species whose common members includeA. flavus andA. parasiticus. These are well-known for the production of aflatoxin (AF) B and G and other toxic metabolites, like cyclopiazonic acid (CPA). They are saprophytic soil dwellers and also become crop opportunistic epiphytes. The consequence is contamination of the crop with mycotoxins, such as carcinogenic AF. We investigated theFlavi community structure of maize and that of their surrounding soil, including their mycotoxigenicity. Furthermore, we investigated the link of the maizeFlavi diversity with preharvest maize AF levels. The study was carried out in four selected districts of Zambia, in a low rainfall zone. TheFlavi characterisation was triphasic, involving morphological (colony colour and sclerotia formation), metabolic (AF and CPA production) and genetic (calmodulin gene polymorphism) analyses.Flavi abundance was determined by dilution plate technique on modified rose Bengal agar. Results showed thatFlavi communities on maize and in soil differed. Maize had a higherFlavi species diversity than soil.A. parasiticus dominated the soil community by frequency of field appearance (85%), while maize was dominated byA. minisclerotigenes (45%). CPA-producers with or without AF production dominated the maize (65%) while producers of only AF (B/G) dominated the soil (88%). The ratio between maizeA. parasiticus andA. minisclerotigenes abundance seemed to have had...
Source: Mycotoxin Research - Category: Toxicology Source Type: research