Characterization of Acidovorax citrulli virulence on watermelon and melon

Abstract

Acidovorax citrulli is the causal agent of bacterial fruit blotch (BFB) of cucurbits whose population can be distinguished into two groups (I and II). The goal of this research was to further characterize the differences between these groups. We observed no difference in temporal population growth dynamics between AAC00-1 (group II) and M6 (group I) on watermelon and melon. In contrast, in a natural infection assay relative BFB incidence on melon seedlings exposed to group II A. citrulli strains was significantly lower (~ 14.5 %) than on melon seedlings exposed to group I strains (~ 85.3 %), or watermelon seedlings exposed to group I and II strains (81.7 % and 82.3 %, respectively). We also investigated the role of the type III effector AvrBsT from AAC00-1 by expression in M6 and found decreased virulence of the mutant on watermelon and melon seedlings relative to wild-type AC00-1 and M6 strains.