The goal of this study was to determine whether
bacterial antagonists could be used to control Xanthomonas citri subsp
citri (Xcc), the causal agent of bacterial citrus canker disease. A
total of 22 potentially bacterial antagonists isolated as epiphytes from the
phylloplane of healthy citrus trees were screened for their in vitro biological
control capability against Xcc. These strains were identified as  Pseudomonas  fluorescens   on
the basis of biochemical and physiological tests and 16S rDNA. Out of these 22
potentially bacterial antagonists, five strains (KSA1, KSA9, KSA14, KSA17, and
KSA20) showed high potential growth inhibition capabilities against Xcc.
The KSA1 strain was selected for further studies to test its in vivo
capability to control bacterial citrus canker pathogen. It was sprayed in a
suspension of 107
CFU ml-1
on citrus leaves which were subsequently inoculated after 72 h with 108 CFU ml-1 suspension of Xcc strain JQ890095.
According to the in vivo biocontrol tests, the putative antagonist KSA1
significantly reduced the symptoms on the leaves of Mexican lime seedlings
compared with untreated inoculated plants.