Reason for crown gall and hairy root disease?
Smith and Townsend (1907) found A.tumefaciens as the causative agent of crown gall disease. A.tumefaciens has a 200kb plasmid called as Ti plasmid (tumor inducing plasmid) which is responsible for crown gall disease.
A.rhizhogenes has a plasmid called as Ri plasmid (root hair inducing plasmid) which is responsible for hairy root disease.