Biological Control of Grape Crown Gall with Non-tumorigenic Agrobacterium vitis Strain F2/5

Abstract

A non-tumorigenic strain (F2/5) of Agrobacterium vitis produces an agrocin that inhibited in vitro growth of 21 of 25 A. vitis, two of 10 A. tumefaciens biovar 1, and none of nine biovar 2 strains. It inhibited both tumorigenic and non-tumorigenic strains. When applied to wounds on potted woody grape trunks ( Vitis vinifera L. cvs. Chardonnay and Riesling) in the greenhouse, the gall sizes were significantly reduced for seven of 10 A. vitis, one of two A. tumefaciens biovar 1 and one of one biovar 2 strains. The numbers of inoculation sites at which galls developed was reduced for all but one A. vitis strain. There is a good, but not perfect, correlation between in vitro sensitivity to the agrocin and control in vivo. Co-inoculation of F2/5 with pathogen was as effective or more effective in most cases than pre-inoculation of F2/5. When pathogen was inoculated prior to F2/5, the level of control was greatly reduced. Control was most effective when equal concentrations of F2/5 and pathogen were inoculated and declined for ratios of 1:10 and 1:100 (F2/5 to pathogen). F2/5 contains three plasmids, none of which hybridize with a probe, pTHE17, consisting of the T-DNA from A. tumefaciens strain C58.