Colonization dynamics of Acidovorax citrulli in melon

Abstract

The aim of this work was to investigate the ability of Acidovorax citrulli, the causal agent of bacterial fruit blotch (BFB) of cucurbits, to colonize melon tissues. Under greenhouse conditions leaves and seeds were inoculated with a spontaneous mutant of A. citrulli (group I) resistant to rifampicin (Ac1Rif), and samples of hypocotyls, cotyledonary leaves, roots, leaves and stems were processed at three-day intervals. When the 1st pair of melon leaves had been inoculated, A. citrulli was only detected until the 10th pair of leaves (1.3 x 103 CFU g-1 of leaf) and the consecutive stem (3.3 x 103 CFU g-1 of stem) on the 30th day. However, after seed inoculation A. citrulli colonized the hypocotyl, roots, cotyledonary leaves, leaves and stems and was only detected until the 4th pair of leaves (1.62 x 102 CFU g-1 of leaf) and the consecutive stem (9.1 x 101 CFU g-1 of stem) on the 24th day post-inoculation. In conclusion, A. citrulli colonized different parts of the melon plant over time, depending on its initial location, leaves or seed. This confirms what has been observed in the field, that expanded leaves and stems are the main inoculum sources for melon blossoms and fruit, therefore providing scientific bases for developing more effective strategies for BFB management.