Classification of Phytopathogenic Bacteria
According to the 8 th Ediction of Bergy’s Manual
Phytopathogenic bacteria are classified as:
Division II: Sctobacteria (indifferent to light)
Class I: The Bacteria
Part: Gram negative aerobic rods and cocci.
Genera: 1. Pseudomonas
Cells single, straight or curved rods but not helicie, generally 0.5 X 1.5 to 4 microns in size, motile by polar flagella one or more in number, non spore forming, gram negative; strict aerobes ; chemoorganotrophs; metabolism respiratory, never fermentative.
1. Pseudomonas solanacearum causes brown rot or wilt of potatoes.
2. Pseudomonas rubrillineans causes red stripe of sugarcane.
Cells single, straight rods measuring 0.2 to 0.8 X 0.6 to 2.0 microns ( Usually 0.4X 1.0 microns); Gram –ve , motile by a single polar flagellum; non spore forming; copious extracellular slime produced; strict aerobes; metabolism respiratory, never fermentative ; oxidase negative and catalase positive; bacterial colonies yellow coloured due to production of Xanthomonadin pigment.
1. X. campestris pv. Citri causes citri cause citrus canker.
2. X. campestris pv. Malvacearum causes angular leaf sport and black arm of cotton.
3. X. campestris pv. Oryzae causes bacterial leaf blight of rice.
The bacteria are rod shaped, 0.8 X 15. m. They are motile by means of 1.4 peritrichous flagella, when only one flagellum is present it is more often lateral than polar. When growing on carbohydrate – containing media the bacteria produce abundant polysaccharide slime. The colonies are non-pigmented and usually smooth. These bacteria are rhizosphere and soil inhabitants.
Agrobacterium tumefaction causes crown gall of pome and stone fruit trees, brambles and grapes.
A. rubi causes cane gall of raspberries and black berries.
A. rhizogenes causes hairy root of apple.
Gram Negative, Facultative Anaerobic Rods
Cells predominantly single, straight rods, measuring 0.5 to 1.0 X 1.0 to 3.0 microns; motile (Except E.stewartii and E.dissolves) by peritrichous flagella; gram negative ; grows well on artificial media aerobically as well as anaerobically and produce acid. The genus has three major groups of species.
i) Pectolytic bacteria that cause oft rot.
ii) Those do not cause soft rot but dry necrosis and wilt and
iii) Epiphytes that cause neither soft rot nor necrosis.
1. E. amylovora causes fire blight of apple.
2. E.tracheiphia causes vascular wilt of cucurbits.
3. E.carotovora pv. atroseptica causes black leg of potato.
4. E. carotovora pv. Carotovora causes soft rot numerous fleshy fruits, vegetables and ornamentals.