Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2017
Publication Date: N/A
Technical Abstract: In this study we sequenced the genomes of 60 Fusarium graminearum, the major fungal pathogen responsible for Fusarium head blight (FHB) in cereal crops world-wide. To investigate adaptive evolution of FHB pathogens, we performed population-level analyses to characterize genomic structure, signatures of natural selection, and differences in gene content among isolates. Genome-wide patterns of SNP diversity revealed that most isolates with the novel NX-2 (3a-acetoxy, 7a,15-81 dihydroxy-12,13-epoxytrichothec-9-ene) toxin type represent a genetic population (termed NA3) that is distinct from the native (NA1, largely 15-acetyl-deoxynivalenol toxin type) and invasive (NA2, largely 3-acetyl-deoxynivalenol toxin type) populations inhabiting North America, although genetic exchange among populations was documented. The three populations differed in gene content, with 134 genes showing population-specific patterns of conservation. In addition, each population had unique genetic signatures of adaptive selection that were largely focused in hypervariable regions of chromosomes. Sixteen candidate loci, varying in size from 10-40 kb, showed genetic signals of adaptive divergence, in that alleles were highly differentiated among populations but showed reduced diversity within populations. The strongest signals of selective sweeps were observed at the trichothecene biosynthetic gene cluster. However, functional annotation of population-differentiating genomic regions revealed numerous genes involved in host invasion, toxin production, and secondary metabolism, and implicated plant hosts, microbial competitors, and temperature and light as major drivers of adaptive divergence. Collectively, our results show that North American populations of F. graminearum harbor unique sets of adaptations that contribute to differences in how these pathogens exploit the agricultural landscape.