Systematic position.Kingdom Procary

Systematic position.
Kingdom Procaryotae, section Gram-negative aerobic rods and cocci, family Pseudomonodaceae, genus Xanthomonas.

Synonyms.
Xanthomonas campestris (Pammel) Dowson.

Biological group.
Hemibiotroph.

Morphology and biology.
The Pathogen causes vascular disease. It attacks plants of all ages through leaf pores and mechanical injuries to plants. The plants lag behind in growth with their leaves turning yellow. Characteristic attributes of the disease are dark-colored vascula of leaves, pedicles, and cabbage-stumps. They are easily visible at cross-section. The disease is more strongly shown in a phase of leaf rosette and head formation than in a phase of pod formation and seed maturing. Withering of the bottom leaves is also an important symptom of this disease. Infected leaves can fall down one by one. Infection of healthy adult plants during vegetation promotes the disease distribution from a place of primary infection (from plant leaf margin) at the sharp angle directed by its top, toward the plant leaf center. Symptoms of the disease are shown as yellowing of infected leaf tissue. Cells of X. campestris pv. campestris are straight bacilli, usually 0.5-0.8 x 1.0-2.0 mkm, moving by means of simple polar flagella. Gram-negative. Aerob. Non-sporing. Not having resting stage. On potato agar, colonies are round, smooth, brilliant, with even border. Diluting gelatin. Curdling milk (with the subsequent peptonization). Not reducing nitrates. Hydrolyzing starch. Producing acid from dextrose, galactose, arabinose, xylose, maltose, saccharose, raffinose, glycerol, mannitol. Catalase reaction is positive and oxidase reaction is negative. Optimum temperature is 25-30°C, maximum 38-39°C, minimum 5°C. The main sources of the bacteriosis primary infection are vegetation residues and seeds. Pathogen survives in seeds until the following season. The infection can be transferred by means of watering, rain drops, dust, agricultural tools, animals, and insect pests.

Distribution.
The Vascular Bacteriosis of Cabbage is present in the countries of American and African continents, in Australia, Poland, Hungary, Romania, England and others. The disease is widely distributed in all territories of the former Soviet Union where this culture is growing.

Ecology.
Optimum conditions for this bacteriosis development are temperatures of 20-24°C and air humidity 80-100%. The disease develops especially well in hot summers with plentiful rains; the incubation period lasts 10-13 days in the field.
Economic significance.
Pathogen attacks crucifer plants, cultural ones (all species of cabbage, Lepidium sativum, Mattiola spp., Raphanus sativus, Rorippa armoraela f. crusiferae, Boerhaavia erecta f. nyctanaceae) and weeds (Lepidium virginicum, Raphanus raphanistrum, Sinapis nigra, Coronopus didymus, Rorippa palustris, Barbarea vulgaris, Capsella bursa-pastoris). In the central zone of the Russian Federation (Moscow Region), the disease distribution reaches 90-100% (at the disease development about 40-47%) in epiphitotic years. In the Chernozhem zone (Voronezh Region), 15-53% of plants are infected in early varieties and 6-8% ones in mid-season and late varieties. In the Western Siberian zone (Altai Territory, Omsk Region, etc.) affection of plants often exceeds 10-25% depending on growing varieties. In Belarus, 50-80% of plants are diseased in some years. In Kazakhstan, the amount of infected plants is 17-24% in mid-summer, reaching 27-48% at the end of vegetation. In Ukraine, 10-25% or more plants are affected by this bacteriosis in some years. Control measures include maintenance of crop rotation, disinfecting seeds by pesticides, cultivation of resistant varieties, planting of high quality seed material, careful collection and destruction of vegetation residues, struggle and removal of weed plants. Highly precise serological tests are very important for the pathogen diagnostics in seed material.