A crown gall is described as being caused by which type of organism?

A crown gall is described as being caused by which type of organism?

• A. Virus
• B. Fungus
• C. Bacterium
• D. Nematode

Answer: (C)

Crown gall is caused by a bacterium. This disease results from infection by Agrobacterium tumefaciens, a soil-dwelling bacterium that enters plant tissue through wounds and transfers a piece of its Ti (tumor-inducing) plasmid into plant cells. That DNA reprograms the plant cells to divide uncontrollably, producing tumor-like galls on stems and roots. This bacterial origin is why the disease is not due to a virus, fungus, or nematode. Management focuses on using disease-free stock, sanitizing tools to prevent spread, selecting resistant varieties when available, and employing biological controls that target this bacterium.

Crown gall is caused by a bacterium. This disease results from infection by Agrobacterium tumefaciens, a soil-dwelling bacterium that enters plant tissue through wounds and transfers a piece of its Ti (tumor-inducing) plasmid into plant cells. That DNA reprograms the plant cells to divide uncontrollably, producing tumor-like galls on stems and roots. This bacterial origin is why the disease is not due to a virus, fungus, or nematode. Management focuses on using disease-free stock, sanitizing tools to prevent spread, selecting resistant varieties when available, and employing biological controls that target this bacterium.