Evaluation of the Nonpathogenic Agrobacterium vitis Strain ARK-1 for Crown Gall Control in Diverse Plant Species

The nonpathogenic strain of Agrobacterium (=Rhizobium) vitis ARK-1 is a biological agent able to effectively control grapevine crown gall. In this study, treating apple, Japanese pear, peach, rose, and tomato by soaking the roots in a cell suspension of ARK-1 before planting into soil infected with tumorigenic Agrobacterium spp. reduced the number of plants developing crown gall tumors. Meta-analyses of the results from six field trials of apple, four field trials of Japanese pear, and four field trials of peach, from 2010 to 2013, showed integrated risk ratio (IRR) after treatment with ARK-1 to be 0.38 for apple crown gall, 0.16 for Japanese pear crown gall, and 0.20 for peach crown gall, indicating that the disease incidence was significantly reduced by ARK-1 treatment. Meta-analyses of the results from three greenhouse trials of rose and three greenhouse trials of tomato showed IRR after treatment with ARK-1 to be 0.29 for rose crown gall and 0.16 for tomato crown gall, indicating that the disease incidence was significantly reduced by ARK-1 treatment. These results indicated that control by ARK-1 covers five different species of host plants and tumorigenic (Ti) strains of Agrobacterium species.