Plant growth promotion and bacterial canker control of Lycopersicon esculentum L. cv. Campbell 33 by biocontrol agents

Endophytic and epiphytic bacteria have been reported as agents of bio-control of diseases and plant growth promotors. Here, in vitro and greenhouse experiments were conducted to evaluate the action of two microbial strains; Aureobasidium pullulans and Pantoea agglomerans, on biocontrol of bacterial canker and growth promotion of tomato (Lycopersicon esculentum cv. Campbell 33). Two frequencies of treatment were used to assess their potential effect (15 and 30 days between two subsequent treatments). The two strains were able to inhibit, in vitro, the growth of Clavibacter michiganensis subsp. michiganensis the causative agent of tomato canker. Also, their antagonistic effects were confirmed in greenhouse conditions. Indeed, bacterial canker incidence in tomato plants treated with A. pullulans and P. agglomerans separately or in mixture was significantly less severe (16%) compared to the positive control (83%). The treatment frequency (intervals of 15 or 30 days) and the choice of strains to inoculate (separated or combined strains) appear to be essential for obtaining significant results. Consequently, both A. pullulans and P. agglomerans strains highly reduced incidence of bacterial canker particularly when tomato plants were treated at a frequency of fifteen days