Biological Control of Grapevine Crown Gall Caused by Allorhizobiumvitis using Bacterial Antagonists

The potential use of bacterial antagonists isolated from different area in Morocco for the biological control of grapevine crown gall caused by Allorhizobium vitis was investigated. In vitro analyzing the activity of 90 bacterial isolates towards Allorhizobium vitis strain S4 resulted in a selection of 26 biocontrol agents. The isolated were tested for their ability in vitro to inhibit the growth of the pathogen. Among these isolates 12 antagonists are efficient. Molecular identification of selected isolates, using rDNA 16S sequencing, show that the antagonists belong to different genera as Bacillus spp. , Pantoea sp. , Rahnella sp. , Acinetobacter spp. and Enterobacter sp. Four antagonists were tested for their antagonistic effect in planta, they exhibited considerable inhibitory activity to reduce the incidence of galls in tomato and squash fruits. Rahnella aquatilis and Pantoea agglomerrans reduced the incidence of crown gall up to 100 % both in tomato and squash fruits. Bacillus subtilis reduced the incidence of gall development to 75 % in squash fruits and 60 % in tomato. Whereas, Acinetobacter calcoaceticus reduced incidence of gall formation to 65 % in squash fruits and 47 % in tomato. Consequently, the treatment with bacterial antagonists may be used as an effectiveness alternative to control crown gall disease.