Invited Presenter

Mark L. Farman ¹
1. University of Kentucky, Department of Plant Pathology, Lexington, KY
Corresponding Author: Mark Farman, farman@uky.edu

Farman, Mark

farman@uky.edu

Fusarium graminearum has been reported to possess a “two-speed” genome, with fast-evolving compartments exhibiting elevated nucleotide diversity and enrichment in genes associated with pathogenicity and preferentially expressed in planta. However, the evolutionary processes that gave rise to this two-speed genome—and the forces maintaining conserved positions of compartments across strains—remain poorly understood. Although admixture has been suggested to play only a minor role in F. graminearum population structure, published phylogenetic trees and split-network analyses instead suggest that the reshuffling of standing variation acquired through admixture is the dominant evolutionary force. This prediction was confirmed using genome-wide scans, which revealed that the fast-evolving compartments comprise sequences introgressed from other species within the F. graminearum species complex, including F. asiaticum, F. austroamericanum, F. boothii, F. cortaderiae, F. gerlachii, F. louisianense, and F. meridionale. Intriguingly, while the fast compartments imply extensive gene flow among the NA1, NA2, and NA3 lineages, the slow compartments suggest that such exchange is largely absent. This compartment-specific pattern of gene flow presents an evolutionary conundrum that challenges traditional models of speciation.

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