Founder events influence structures of Aspergillus flavus populations

Abstract

Summary In warm regions, agricultural fields are occupied by complex Aspergillus flavus communities composed of isolates in many vegetative compatibility groups (VCGs) with varying abilities to produce highly toxic, carcinogenic aflatoxins. Aflatoxin contamination is reduced with biocontrol products that enable atoxigenic isolates from atoxigenic VCGs to dominate the population. Shifts in VCG frequencies similar to those caused by the introduction of biocontrol isolates were detected in Sonora, Mexico, where biocontrol is not currently practiced. The shifts were attributed to founder events. Although VCGs reproduce clonally, significant diversity exists within VCGs. Simple sequence repeat (SSR) fingerprinting revealed that increased frequencies of VCG YV150 involved a single haplotype. This is consistent with a founder event. Additionally, great diversity was detected among 82 YV150 isolates collected over 20 years across Mexico and the United States. Thirty‐six YV150 haplotypes were separated into two populations by Structure and SplitsTree analyses. Sixty‐five percent of isolates had MAT1‐1 and belonged to one population. The remaining had MAT1‐2 and belonged to the second population. SSR alleles varied within populations, but recombination between populations was not detected despite co‐occurrence at some locations. Results suggest that YV150 isolates with opposite mating‐type have either strongly restrained or lost sexual reproduction among themselves.

Distribution of active ingredients of a commercial aflatoxin biocontrol product in naturally occurring fungal communities across Kenya

“…Results from the SSR assay were in complete agreement with VCG analyses used to track other atoxigenic A. flavus and, as such, this assay is also a reliable tool (Cotty, 1994a,b; Atehnkeng et al ., 2014; Ortega‐Beltran and Cotty, 2018; Agbetiameh et al ., 2019). Vegetative compatibility groups are clonal lineages (Papa, 1986; Leslie, 1993), and linkage equilibrium of SSR loci occurs among isolates within the same VCG, possibly indicating an active parasexual cycle, but not among isolates in different VCGs (Grubisha and Cotty, 2010; Grubisha and Cotty, 2015; Ortega‐Beltran et al ., 2020). Over long periods, mutation and clonal evolution may cause diversity at SSR loci within VCGs (Islam et al ., 2018).…”

“…Fungal VCGs frequently contain multiple closely related SSR haplotypes (Berbegal et al ., 2010; Chang et al ., 2014). SSR markers are valuable tools for genotyping A. flavus from agricultural (Tran‐Dinh et al ., 2009; Grubisha and Cotty, 2010, 2015; Sweany et al ., 2011; Ortega‐Beltran et al ., 2020) and clinical settings (Hadrich et al ., 2010; Dehghan et al ., 2014).…”

Influence of Wounding and Temperature on Resistance of Maize Landraces From Mexico to Aflatoxin Contamination

“…For the temperature/living embryo status experiment, A. flavus isolate SSS06 MN-F, which belongs to vegetative compatibility group (VCG) SON003 from Sonora, Mexico, was used. Members of SON003 also produce large aflatoxin B 1 concentrations and are common in agroecosystems where MLRs used in the current study are cultivated ( Ortega-Beltran and Cotty, 2018 ; Ortega-Beltran et al, 2020 ). Inoculum suspensions were prepared by collecting spores from 5-day-old cultures (31°C) grown on 5-2 agar [5% V-8 juice (Campbell Soup Company, Camden, NJ), 2% Bacto-agar (Difco Laboratories Inc., Detroit, MI), pH 5.2] with a cotton swab into sterile distilled deionized water.…”

Development and scale-up of bioprotectants to keep staple foods safe from aflatoxin contamination in Africa

“…There is great variation within and among fields, in both small and large areas, within cropping systems and across years (Bayman and Cotty, 1991;Mehl et al, 2012;Ortega-Beltran and Cotty, 2018). Community structures dominated by certain genotypes or species for 1 year may change dramatically within a relatively short term (Drott et al, 2019;Ortega-Beltran et al, 2020).…”

“…Moore, sp. nov.) -through laboratory manipulation -the species is considered to reproduce predominantly in an asexual manner (i.e., through spores) (Islam et al, 2018;Ortega-Beltran et al, 2020;Papa, 1986). Sexual recombination is not significant in field conditions.…”