Identification and characterization of strains of Gibberella fujikuroi mating population A with rare fumonisin production phenotypes

Abstract

A survey of 245 strains of Gibberella fujikuroi mating population A (anamorph Fusarium moniliforme) isolated primarily from maize and sorghum in North America identified strains with three rare fumonisin production phenotypes. In liquid culture and on a maize solid substrate, several strains produced fumonisin B₂ (FB₂) or B₃ (FB₃), but not fumonisin B₁ (FB₁), suggesting a defect in hydroxylation of C-5 or C-10. Several strains were nonproducers of fumonisins in liquid culture and low producers of fumonisins (0–600 μg/g FB₁, FB₂ and FB₃) on maize substrate. The heritability of fumonisin production on maize was studied by crossing fumonisin low-producing and non-producing strains with fumonisin high-producing strains. Random ascospore and tetrad progeny were analyzed by gas chromatography-mass spectroscopy and high performance liquid chromatography for their ability to produce fumonisins on maize substrate. Although most of these crosses were poorly fertile, in one cross the ability to produce high levels of fumonisins segregated as a single gene, designated fum4, or group of closely linked genes. Allelism tests showed that fum4 was linked to, but not allelic with, the fumi locus that was previously identified in strains of mating population A from Nepal.

Key Words:

• fumonisins
• Fusarium moniliforme
• Gibberella fujikuroi
• maize
• mycotoxins