Characterization of Fusarium avenaceum from lupin in central Alberta: genetic diversity, mating type and aggressiveness

Abstract

Root rot, caused by Fusarium avenaceum (teleomorph: Gibberella avenacea), is an important disease of lupin (Lupinus angustifolius) and other crops in western Canada. Fusarium isolates collected from infected roots of lupin in central Alberta were characterized using two RAPD primers, three microsatellite-primed PCR markers, diagnostic primers for putative mating type, sequence comparison of the translation elongation factor 1α (EF1α) and internal transcribed spacer (ITS) region, and assessments of aggressiveness on lupin seedlings. The teleomorph phase of F. avenaceum has been reported only twice in the world, but both mating types were found throughout the province. Isolates of mating type 2 were slightly more aggressive than mating type 1 on five lupin cultivars. All 42 isolates of F. avenaceum assessed in this study had a unique multilocus genotype, which indicates a high level of genotypic diversity in the pathogen population. Cluster analysis did not reveal an association between the geographic location of the isolates and genetic relatedness based on genetic markers. Instead, the F. avenaceum isolates divided into two distinct groups, with isolates from both groups occurring together at many sites. Phylogenetic analysis also revealed high diversity and the presence of some European-like isolates within the Canadian pathogen population. The high genotypic diversity of isolates and the presence of both mating types across sites provide an indication that sexual reproduction may occur within populations of F. avenaceum in Alberta.