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The phylogenetics of mycotoxin and sclerotium production in Aspergillus flavus and Aspergillus oryzae

D M Geiser1, J W Dorner, B W Horn

  • 1Department of Plant Pathology, The Pennsylvania State University, 204 Buckhout Laboratory, University Park, Pennsylvania 16802-4507, USA. dgeiser@psu.edu

Fungal Genetics and Biology : FG & B
|March 29, 2001
PubMed

Insights

Phylogenetic analysis of Aspergillus flavus reveals deep divergence between groups I and II, correlating with aflatoxin production and sclerotium size. Group II strains produced more aflatoxins and were smaller.

Area of Science:

  • Mycology
  • Genetics
  • Agricultural Science

Background:

  • Aspergillus flavus is a significant agricultural and health threat due to aflatoxin production.
  • A. flavus exhibits two phylogenetic subgroups (I and II) and two morphological types (S and L sclerotium size).
  • The non-aflatoxigenic fungus A. oryzae is phylogenetically within A. flavus group I.

Purpose of the Study:

  • To investigate the phylogenetic relationships within A. flavus.
  • To correlate phylogenetic groups with aflatoxin production and morphological characteristics.
  • To explore the genetic basis of aflatoxin biosynthesis and non-production.

Main Methods:

  • Sequencing of three gene regions, including the aflatoxin biosynthesis gene omt12, in 33 A. flavus strains, 3 A. oryzae, and 2 A. parasiticus isolates.
  • Analysis of B and G aflatoxin and cyclopiazonic acid production.
  • Morphological classification of isolates into "S" and "L" sclerotium size groups.

Main Results:

  • Phylogenetic analysis confirmed deep divergence between A. flavus groups I and II.
  • Group II strains predominantly produced both B and G aflatoxins and exhibited the "S" phenotype.
  • Group I strains showed varied aflatoxin production (mostly B) and included both "S" and "L" phenotypes; some non-aflatoxigenic strains shared omt12 alleles with A. oryzae.

Conclusions:

  • Phylogenetic divergence in A. flavus is strongly linked to aflatoxin production capabilities and morphology.
  • The omt12 gene region provides insights into the evolution of aflatoxin production and non-production within A. flavus.
  • Understanding these genetic and phenotypic variations is crucial for managing aflatoxin contamination in agriculture.

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