Effect of potential biocontrol agents selected among grapevine endophytes and commercial products on crown gall disease

The current strategies for the control of Agrobacterium vitis crown gall in grape are generally unsuccessful once the pathogen has established in vineyards. Experimental trials were conducted to evaluate the effectiveness of treatments based on nonpathogenic endophytes isolated from asymptomatic grapevines growing in vineyards with high incidence of crown gall and on microorganisms isolated from commercial products. Two-year in planta trials conducted on rootstocks treated with endophytic isolates showed the effectiveness of two bacterial endophytes, both in the genus Curtobacterium, and one fungal isolate in the genus Acremonium in reducing crown gall development. For the commercial biological control agents, Bacillus subtilis SR63 and Trichoderma asperellum T1 were the most effective strains against A. vitis, indicating commercial products could be reserves to draw upon to identify useful biocontrol agents. Based on the combination of data in this work,microorganisms, both endophytes and those formulated in commercial products, were identified that can potentially be exploited for the control of grapevine crown gall disease.