Bacterial fruit blotch: A threat to the cucurbit industry

Bacterial fruit blotch (BFB) of cucurbits is caused by the Gram-negative bacterium Acidovorax avenae subsp. citrulli. The disease gained importance in the late 1980s, after devastating outbreaks in watermelon fields in several states in the US. Since then, BFB has spread worldwide, and has been reported in other cucurbits such as melon, pumpkin, squash, and cucumber. A. avenae subsp. citrulli is a seedborne pathogen of highly destructive potential. Under favorable conditions, the bacterium spreads rapidly throughout nurseries and in the field, leading to seedling blight or, at a later stage, fruit rot. Strategies for managing BFB are limited and there are no reliable sources of BFB resistance. The disease therefore represents a serious threat to the cucurbit industry. Despite its economic importance, there is little knowledge on basic aspects of the pathogen's biology or on the molecular basis of BFB pathogenesis. Recently, the genome sequence of one A. avenae subsp. citrulli strain was released, making a great contribution to the investigation of basic aspects of BFB. A better understanding of these aspects will contribute to improved screens for BFB resistance and to the development of more effective strategies to manage this threatening disease.