Date of Graduation

Fall 2025

Degree

Master of Science in Plant Science

Department

School of Agricultural Science & Conservation

Committee Chair

Wenping Qiu

Abstract

Crown gall disease can be very detrimental to grape and wine producers around the world by reducing vine vigor and yield. It is caused by the bacteria Allorhizobium vitis (A. Vitis) carrying a tumor inducing (Ti) plasmid. The A. vitis bacteria have been found in soil and cane tissues in vineyards around the world, and infect all cultivated grapes. However, there have been no reports of crown gall on native wild grapevines, and very little is known about the ecology of A. vitis in native ecosystems. I have sampled cambium tissues from three native wild grape species of Missouri (Vitis vulpina, Vitis rupestris, and Vitis cinerea) as well as soil samples from the growing area to investigate the ecological relationship that A. vitis has with these wild vines. I found that genetic markers for the A. vitis associated Ti plasmid, RepB and VirD, are present in all wild grape species, but no symptoms of crown gall were observed. The presence of Ti plasmid markers is more prevalent in V. rupestris and V. cinerea than in V. vulpina, with V. vulpina being almost completely absent of virulent plasmid markers. These observations remain true even when V. vulpina and V. rupestris are growing at the same site. The presence of the PehA marker, representing A. vitis chromosome, is mainly confined to V. rupestris. This suggests a high degree of genetic diversity in wild A. vitis strains in the native ecosystems. The differences in A. vitis detection among the species as well as the lack of tumors imply the existence of multiple resistance mechanisms. These results set a steppingstone in understanding the ecological niche A. vitis holds in the native ecosystem and in designing control strategies to protect cultivated grapevines from infection by A. vitis in vineyards.

Keywords

Allorhizobium vitis, microecology, endophytes, tumor inducing (Ti) plasmid, crown gall, grapevines, native grapevines, disease resistance

Subject Categories

Biodiversity | Botany | Evolution | Other Ecology and Evolutionary Biology | Plant Biology | Viticulture and Oenology

Copyright

© Hunter White

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