The Aerobiology and Population Genetic Structure of Gibberella zeae

Abstract

Gibberella zeae causes Fusarium head blight (FHB) of wheat and barley and Gibberella ear rot (GER) of corn. Ascospores of G. zeae rely on atmospheric motion systems for transport to susceptible host plants. A long term objective of our research is to determine where inoculum for FHB and GER comes from and how far it travels. We measured the distance that ascospores of G. zeae were forcibly discharged in still air, and determined that long-range transport is favored by day-time ascospore release. We used remote-piloted aircraft to collect viable spores of G. zeae in the lower atmosphere. Viable spores of G. zeae were abundant in the lower atmosphere during all times of the day and night under a broad range of environmental conditions. Viable spores of G. zeae were deposited over wheat and corn fields mainly at random and predominantly at night. We used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of atmospheric populations of G. zeae over multiple years. Genotypic diversity was high in the atmospheric populations of G. zeae, and nearly all of the isolates in each of the populations represented unique AFLP haplotypes. Diverse atmospheric populations of G. zeae are indicative of wellmixed sources of aerial inoculum, potentially originating from local and more distant sources. Introduced strains of G. zeae with altered virulence or mycotoxin profiles, moving over long distances, have the potential to spread rapidly into previously unexposed wheat and corn production regions. Accepted for publication 14 February 2007. Published 26 July 2007.