Biological control of Agrobacterium vitis using non-tumorigenic agrobacteria

The potential use of non-tumorigenic agrobacteria for the biological contro l of grapevine crown gall in Italy was investigated. Four Agrobacterium str ains belonging to the species radiobacter and vitis were used to protect th e susceptible cv. Malvasia Istriana grafted on the rootstock 420 A. Moreove r, the effect of each treatment on grapevine vitality and growth was assess ed, including the percentage of marketable vines, as determined by industry standards. Treatments with the antagonists clearly reduced tissue coloniza tion by the pathogen, with a drop of more than 100-fold in pathogen populat ions in the samples collected at the graft point. Another important effect was the reduction of internal necrosis possibly induced by the high concent ration of the nopaline strain CG 49 used in the experiments. According to v iticultural and commercial parameters, treatments with the antagonists impr oved the quality of the vines, with fewer discards and a high percentage of marketable material. Therefore, these antagonists can be considered benefi cial for grapevine.