title: Enhanced diversity and aflatoxigenicity in interspecific hybrids of Aspergillus flavus and Aspergillus parasiticus.
abstract: Aspergillus flavus and A. parasiticus are the two most important aflatoxin-producing fungi responsible for the contamination of agricultural commodities worldwide. Both species are heterothallic and undergo sexual reproduction in laboratory crosses. Here we examine the possibility of interspecific matings between A. flavus and A. parasiticus. These species can be distinguished morphologically and genetically, as well as by their mycotoxin profiles. Aspergillus flavus produces both B aflatoxins and cyclopiazonic acid (CPA), B aflatoxins or CPA alone, or neither mycotoxin; Aspergillus parasiticus produces B and G aflatoxins or the aflatoxin precursor O-methylsterigmatocystin, but not CPA. Only four of forty-five attempted interspecific crosses between opposite mating types of A. flavus and A. parasiticus were fertile and produced viable ascospores. Single ascospore strains from each cross were shown to be recombinant hybrids using multilocus genotyping and array comparative genome hybridization. Conidia of parents and their hybrid progeny were haploid and predominantly monokaryons and dikaryons based on flow cytometry. Multilocus phylogenetic inference showed that experimental hybrid progeny were grouped with naturally occurring A. flavus L strain and A. parasiticus. Higher total aflatoxin concentrations in some F1 progeny strains compared to midpoint parent aflatoxin levels indicate synergism in aflatoxin production; moreover, three progeny strains synthesized G aflatoxins that were not produced by the parents, and there was evidence of allopolyploidization in one strain. These results suggest that hybridization is an important diversifying force resulting in the genesis of novel toxin profiles in these agriculturally important fungi.
authors.affiliation: Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Olarte
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Worthington
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Horn
authors.forename: Geromy G
authors.initials: GG
authors.lastname: Moore
authors.forename: Rakhi
authors.initials: R
authors.lastname: Singh
authors.forename: James T
authors.initials: JT
authors.lastname: Monacell
authors.forename: Joe W
authors.initials: JW
authors.lastname: Dorner
authors.forename: Eric A
authors.initials: EA
authors.lastname: Stone
authors.forename: De-Yu
authors.initials: DY
authors.lastname: Xie
authors.forename: Ignazio
authors.initials: I
authors.lastname: Carbone
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis*; D001230:Aspergillus / Q000145:classification / Q000235:genetics*; D001231:Aspergillus flavus / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D049770:Genes, Mating Type, Fungal; D005838:Genotype; D060005:Genotyping Techniques; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013241:Sterigmatocystin / Q000031:analogs & derivatives / Q000096:biosynthesis
chemical_list: D000348:Aflatoxins; D013241:Sterigmatocystin; C039904:O-methylsterigmatocystin
keywords: allopolyploid; array comparative genome hybridization; flow cytometry; meiosis; population