Ti plasmids are divided into 4 groups depending upon the types of opines that are synthesized.
1) Nopaline plasmids: These carry genes for synthesis of nopaline in tumors and for utilizing it in bacteria. The tumors carrying nopaline plasmids can differentiate into shoots with abnormal structures. They are called teratomas as they are analogous to certain mammalian tumors.
2) Octopine plasmids: The octopine tumors are undifferentiated and do not produce teratoma shoots.
3) Agropine plasmids: The tumors carrying agropine plasmids do not differentiate. They are poorly developed and die early.
4) Ri plasmids: These induce hairy root disease on some plants. They carry agropine genes. May also contain segments of both nopaline and octopine plasmids.