The role of bacterial motility in watermelon blossom colonization and seed infestation by Acidovorax avenae subsp. citrulli, causal agent of bacterial fruit blotch
Lessl, Jason Thomas
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Acidovorax avenae subsp. citrulli, causal agent of bacterial fruit blotch (BFB), is a devastating disease of watermelon. The most important inoculum source for BFB is watermelon seeds. A. avenae subsp. citrulli invades female watermelon blossoms and infests seeds without causing symptoms in fruit or blossom. Effective management of BFB depends on an accurate understanding of how A. avenae subsp. citrulli invades blossoms and infests seeds, which was the purpose of this study. A. avenae subsp. citrulli was observed to colonize female watermelon blossoms and this phenomenon offers a possible explanation of how seed infestation occurs under natural conditions. Interestingly, the blossom colonization phase was not characteristic of pathogenic growth and A. avenae subsp. citrulli cells were limited to transmitting tissues of the blossom. A. avenae subsp. citrulli motility appeared to play no role in ovary invasion, however, once in the ovary, it increased levels of seed infestation.