Analysis of the competitiveness between a non-aflatoxigenic and an aflatoxigenic Aspergillus flavus strain on maize kernels by droplet digital PCR

AbstractNon-aflatoxigenicAspergillus flavus strains are used as a biocontrol system on maize fields to decrease the aflatoxin biosynthesis of aflatoxigenicA. flavus strains.A. flavus strain AF36 was the first commercially available biocontrol strain and is authorized for use on maize fields by the US Environmental Protection Agency, e.g., in Texas and Arizona. A droplet digital PCR (ddPCR) assay was developed to analyze the mechanisms of competition and interaction of aflatoxigenic and non-aflatoxigenicA. flavus strains. This assay enables the parallel identification and quantification of the biocontrol strainA. flavus AF36 and the aflatoxigenicA. flavus strain MRI19. To test the assay, spores of both strains were mixed in varying ratios and were incubated on maize-based agar or maize kernels for up to 20  days. Genomic equivalent ratios (genome copy numbers) of both strains were determined by ddPCR at certain times after incubation and were compared to the spore ratios used for inoculation. The aflatoxin biosynthesis was also measured. In general,A. flavus MRI19 had higher competitiveness in the tested habitats compared to the non-aflatoxigenic strain, as indicated by higher final genomic equivalent ratios of this strain compared to the spore ratios used for inoculation. Nevertheless,A. flavus AF36 effectively controlled aflatoxin biosynthesis ofA. flavus MRI19, as a clear aflatoxin inhibition was already seen by the inoculation of 10% spores of the biocontrol strain mixed ...
Source: Mycotoxin Research - Category: Toxicology Source Type: research