Holmes divides the virus in the three groups–
Phytophaginae (Plant virus)
Zoophaginae (animal virus)
Cistrus tristeza virus. (Largest in all group) It length is 1300 nm.
Smallest plant virus– Satellite tobacco necrosis virus (17 nm).
Longest plant virus - Citrus tristeza virus.
Smallest animal virus - Foot and mouth virus.
Largest animal virus - Pox virus.
Complicated animal virus - Parrot fever virus.
Satellite virus - Virus that depend upon another virus for multiplication called satellite virus.
Satellite tobacco necrosis virus depend upon the tobacco necrosis virus.
Smallest bacteriophage – Coliphage - (2nm). (Smallest virus in all groups).
Largest bacteriophage - Teven phage -