Effect of bioagents and resistance inducers on grapevine crown gall

Abstract

Bioagents and chemicals were applied to one-year old grafted vines (Ancelotta/420A) in glasshouse and field experiments set up at the Vivai Cooperativi Rauscedo (VCR, Pordenone, Italy). In the glasshouse, holes were drilled in vines on the rootstock and the holes were charged with suspensions of different strains of Pseudomonas spp., and with the biofungicides BS-F4 and Serenade, both based on Bacillus subtilis, before inoculation with a vitopine Agrobacterium vitis strain. The growth retardant Regalis and the resistance inducer Bion were applied to the vines two weeks before inoculation with the pathogen. Six months after inoculation, disease incidence was lowest when BS-F4 had been applied. In the field trial, the vines were wounded by making a cut in the crown, after which they were dipped into the antagonist suspensions just before inoculation with the pathogen. In the two weeks before inoculation, the root systems of the vines were dipped into Regalis and Bion solutions at 7 day intervals. Only these resistance inducers and BS-F4 significantly reduced disease severity. The results indicate that a potential for defence against A. vitis may exist even in susceptible grapevine cultivars, and that this potential can be activated by diverse elicitors.