Secreted in xylem (SIX) gene SIX9 is highly conserved in Fusarium oxysporum f. sp. vasinfectum race 4 isolates from cotton in the United States

Abstract

Many Fusarium oxysporum formae speciales produce small, infection-dependent effector proteins called ‘secreted in xylem’ (SIX) proteins. These proteins are secreted into the xylem of a plant during the infection process and are thought to promote virulence. In this study, a collection of Fusarium oxysporum isolates composed primarily of different races of Fusarium oxysporum f. sp. vasinfectum (FOV), was screened for the presence of fourteen SIX effector genes (SIX1-SIX14). Our results showed that some of the most virulent FOV races, FOV4 and FOV7, share a common SIX effector – SIX9. This effector is largely absent in other races of FOV in North America making SIX9 a potential target for rapid detection of these highly virulent FOV strains and enabling race specific FOV quantification in infected host plants.