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 (Ac1 Rif ), and samples of hypocotyls, cotyledonary leaves, roots, leaves and stems were processed at three-day intervals. When the 1 st pair of melon leaves had been inoculated, A. citrulli was only detected until the 10 th pair of leaves (1.3 x 10 3 CFU g -1 of leaf) and the consecutive stem (3.3 x 10 3 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 10 2 CFU g -1 of leaf) and the consecutive stem (9.1 x 10 1 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 © Copyright by the Brazilian Phytopathological Society.