Raspberry crown gall bacterium

Rhizobium rubi (formerly classified under the genus Agrobacterium) is a soil-borne pathogenic bacterium belonging to the Rhizobiaceae family. It is recognized as a significant phytopathogen responsible for inducing crown gall disease in various rosaceous plants, most notably in raspberries and blackberries.

The primary symptom of infection is the formation of galls, or tumor-like growths, on the crown and root systems of the host plants. These galls disrupt the plant's vascular tissue, effectively hindering the translocation of water and essential nutrients from the roots to the upper parts of the plant, leading to stunted growth.

Biologically, the pathogen exploits a mechanism involving the transfer of T-DNA from its Ti-plasmid into the plant cell genome. This genetic modification induces uncontrolled cell proliferation within the host, creating a specialized niche that provides the bacteria with nutrients required for their survival and rapid colonization.

Environmental conditions that favor the development of Rhizobium rubi include moist, neutral to slightly alkaline soils and the presence of fresh wounds on roots. The pathogen can persist in the soil for several years, making it difficult to eradicate once a site is infested with the bacterial population.

Management strategies for this pathogen are strictly preventative. Farmers should prioritize the selection of pathogen-free nursery stock and ensure that pruning and cultivation tools are thoroughly disinfected. Once a plant shows signs of crown gall, it must be removed and destroyed, and susceptible crops should not be replanted in that soil for several years.