Fusarium is a genus of filamentous fungi that contains many agronomically
important plant pathogens, mycotoxin producers, and opportunistic human
pathogens. Comparative analyses have revealed that the Fusarium genome is
compartmentalized into regions responsible for primary metabolism and reproduction
(core genome), and pathogen virulence, host specialization, and
possibly other functions (adaptive genome). Genes involved in virulence and
host specialization are located on pathogenicity chromosomes within strains
pathogenic to tomato (Fusarium oxysporum f. sp. lycopersici ) andpea (Fusarium
‘solani’ f. sp. pisi ). The experimental transfer of pathogenicity chromosomes
from F. oxysporum f. sp. lycopersici into a nonpathogen transformed the latter
into a tomato pathogen. Thus, horizontal transfer may explain the polyphyletic
origins of host specificitywithin the genus. Additional genome-scale
comparative and functional studies are needed to elucidate the evolution and
diversity of pathogenicitymechanisms, whichmay help inform novel disease
management strategies against fusarial pathogens.