Unraveling the Fusarium oxysporum f. sp. fragariae-Strawberry Interaction: Evolution, Infection, and Genetic Resistance.

Fusarium wilt of strawberry, caused by the soil-borne fungal pathogen Fusarium oxysporum f. sp. fragariae (Fof), is one of the greatest threats to cultivated strawberry. The pathogen penetrates strawberry plants through roots, severely affecting roots and crowns and resulting in rapid wilting and death. Research into the genetic basis of resistance to Fof has identified five loci, FW1 - FW5, that confer resistance to Fusarium wilt of strawberry and one Fof effector, SIX6. While it is hypothesized that FW1 recognizes the SIX6 effector, the underlying resistance gene is unknown. A new isolate of Fof that breaks FW1-mediated resistance recently emerged and poses a significant threat to the California strawberry industry, the source of 88-91% of the strawberries produced in the US. There are still significant gaps surrounding the molecular and physiological interaction between Fof and strawberry and the evolution of pathogenicity of Fof isolates unaffected by FW1. This review summarizes our current knowledge, identifies knowledge gaps, and provides a summary of genomic and molecular tools currently available to study the Fof-strawberry interaction.