Abstract
Fusarium avenaceum is a common soil saprophyte and plant pathogen of a variety of hosts worldwide. This pathogen is often involved in the crown rot and head blight of cereals that affects grain yield and quality. F. avenaceum contaminates grain with enniatins more than any species, and they are often detected at the highest prevalence among fusarial toxins in certain geographic areas. We studied intraspecific variability of F. avenaceum based on partial sequences of elongation factor-1 alpha, enniatin synthase, intergenic spacer of rDNA, arylamine N-acetyltransferase and RNA polymerase II data sets. The phylogenetic analyses incorporated a collection of 63 F. avenaceum isolates of various origin among which 41 were associated with wheat. Analyses of the multilocus sequence (MLS) data indicated a high level of genetic variation within the isolates studied with no significant linkage disequilibrium. Correspondingly, maximum parsimony analyses of both MLS and individual data sets showed lack of clear phylogenetic structure within F. avenaceum in relation to host (wheat) and geographic origin. Lack of host specialization indicates no host selective pressure in driving F. avenaceum evolution, while no geographic lineage structure indicates widespread distribution of genotypes that resulted in nullifying the effects of geographic isolation on the evolution of this species. Moreover, significant incongruence between all individual tree topologies and little clonality is consistent with frequent recombination within F. avenaceum.
Highlights
Fusarium avenaceum is a widely-distributed soil saprophyte and plant pathogen of a variety of hosts [1]
Based on an analysis of combined TUB (β-tubulin), ITS and IGS rDNA sequences, F. avenaceum., F. arthrosporioides and F. anguioides isolates were resolved as five separate groups indicating conflict between phylogenetic analysis and the morphological species concept [11]
Previous work by Satyaprasad et al [12] did not reveal a clear separation of groups within F. avenaceum in relation to hosts such as lupin and wheat, based on restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis
Summary
Fusarium avenaceum is a widely-distributed soil saprophyte and plant pathogen of a variety of hosts [1]. F. avenaceum is often involved in crown rot and head blight of barley and wheat [5] This species is the main contaminant of grain with enniatins [6,7]. Recent phylogenetic studies by Nalim et al [13] based on EF1α (elongation factor-1 alpha), TUB and IGS rDNA data sets showed that F. avenaceum isolates pathogenic to lisianthus in the US were not monophyletic or clonal. This situation is characteristic for fungi that reproduce sexually. The studies of Satyaprasad et al [12] and Nalim et al [13]
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