Xanthomonas is a genus of Proteobacteria

Proteobacteria

The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....

, many of which cause plant diseases. Most varieties of Xanthomonas are available from the National Collection of Plant Pathogenic Bacteria

National Collection of Plant Pathogenic Bacteria

The National Collection of Plant Pathogenic Bacteria is a UK Government owned, non-profit-making biological culture collection which specialises in acquiring, authenticating, preserving, and distributing plant pathogenic reference bacteria, and DNA for research in the life sciences...

 (NCPPB) in the United Kingdom and other international culture collections such as ICMP in New Zealand, CFBP in France, and VKM in Russia. It is also taken out from M.T.C.C. India.

Plant pathogenesis

Xanthomonas can infect a wide variety of species including pepper, rice, citrus, cotton, tomato, and soybeans.

Some types of Xanthomonas cause localized leaf spot or leaf streak while others spread systemically and cause black rot or leaf blight disease. They inject a number of effector proteins, including TAL effector

TAL effector

TAL effectors are proteins secreted by Xanthomonas bacteria via their type III secretion system when they infect various plant species...

s, into the plant via their type iii secretion system.