Date of Graduation

Fall 2023


Master of Science in Plant Science (Agriculture)


College of Agriculture

Committee Chair

Wenping Qiu


Crown gall disease causes significant economic loss to the grape and wine industry. Preventive strategies are most effective for mitigating the loss of grapevines in vineyards, as there is no known cure for this disease. The bacterium Allorhizobium vitis carrying a tumor-inducing (Ti) plasmid is the causative agent. A. vitis bacteria live systemically in the grapevine before causing visible symptoms and can survive in residual plant tissues and soil for more than two years. Diagnostic methods have been developed to detect A. vitis bacteria in grapevines and soil. However, more reliable, specific, and high-throughput diagnostics are still needed for screening nursery stocks and soil. We have found primer sets unique to A. vitis on the Ti plasmid’s origin of replication and virulence regions. We have developed procedures and protocols for reliably detecting A. vitis bacteria. We surveyed the incidence of A. vitis in five vineyards and six non-vineyard sites, covering three Missouri AVAs (American Viticultural Areas). We report the distribution of A. vitis in canes and soils within these sites. Our results show that A. vitis bacteria are present near and within the sampled vineyard soil and soils taken from non-vineyard areas across the state. Whether they are tumorigenic requires further investigation. The outcomes from this research will help the grape and wine industry to develop effective strategies for preventing and managing crown gall disease in vineyards.


Allorhizobium vitis, Tumor inducing (Ti) plasmid, RepABC operon, virulence, vir genes, crown gall, grapevine, soil, soil microbes, diagnostics, and detection

Subject Categories

Agricultural Science | Bacteriology | Laboratory and Basic Science Research | Pathogenic Microbiology | Plant Pathology | Viticulture and Oenology


© Jacquelyn M. Wray

Open Access