|Shepherd, Lisa -|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2009
Publication Date: June 30, 2009
Citation: Block, C.C., Shepherd, L.M. 2009. Long-term Survival and Seed Transmission of Acidovorax avenae subsp. citrulli in Melon and Watermelon Seed [abstract]. Phytopathology. 99:S119. Technical Abstract: Seed transmission of Acidovorax avenae ssp. citrulli (Aac) is a key factor in the dissemination of bacterial fruit blotch of cucurbits. In this study, we report seed transmission of Aac from 34-year-old watermelon seed (Citrullus lanatus) and from 40-year-old melon seed (Cucumis melo). The seed lots used for this work were held in refrigerated storage at 4C to 5C for 31 and 33 years, respectively, before being moved to freezer storage at -18C. Each seed lot was planted in a plastic tray and covered with a clear plastic bag supported by a wire frame. The plastic bags helped raise the humidity to near 100% and prevented cross-contamination between trays. Symptomatic plant tissue was tested with ELISA immunostrips, and bacterial isolations were made from positive plants. Pathogenicity testing was done by toothpick inoculations of both 'Edisto' melon and 'Crimson Sweet' watermelon seedlings. Isolates were further confirmed as Aac-positive by PCR. The longest previously reported survival for any seedborne bacterial pathogen was 24 years, for Curtobacterium flaccumfaciens pv. flaccumfaciens from common bean seed. The fact that Acidovorax avenae ssp. citrulli can survive for 40 years or more on seeds indicates that the bacterium is highly tolerant of desiccation and aging. These findings suggest that Acidovorax avenae ssp. citrulli has the potential to survive as long as the seed is viable.