Pseudomonas syringae pv. atrofaciens (McCulloch) Young et al. - Basal Bacteriosis of Wheat.

Systematic position.

Kingdom Procaryotae, section Gram-negative aerobic rods and cocci, family Pseudomonadaceae, genus Pseudomonas.


Bacterium atrofaciens McCulloch, Phytomonas atrofaciens (McCulloch) Bergey et al., Pseudomonas atrofaciens (McCulloch) Stevens.

Biological group.


Morphology and biology.

Bacteriosis attacks leaves, grains, and scales of ears. On leaf plates, brown (not transparent) spots are formed; thus bacterial exudate and film are absent. Early infection frequently causes dwarfism of plants. Leaves dry up at strong lesion of plants, and ears are quite often deformed. The most typical disease symptoms are shown on ear scales. Basis of these scales is painted in dark brown to black. Their narrow internal part darkens at weak lesion; thus, the disease does not show precisely its symptoms. Strong lesion can lead to blackening of all scales. The disease passes to grain at the infection of plants before milky ripeness. Infected grain becomes puny, underdeveloped; thus, the germ perishes. The disease is transferred with seeds; at strong lesion, the seeds decay in ground, or seedlings die off. Cells of P. syringae pv. atrofaciens are straight bacilli, usually 0.6 x 1.0-2.7 mkm, moving by means of 1-4 polar flagella. Gram-negative. Forming capsules. Producing green fluorescing pigment. In beef extract (meat infusion) broth, colonies are white (later gray), round, smooth, brilliant. Diluting gelatin. Peptonizing milk without curtailing. Not restoring nitrates. Producing H2S and indol. Hydrolyzing starch. Forming acid from the media with saccharose, dextrose, galactose, xilose, mannose, glycerin. Not fermenting lactose, maltose, salicine, dulcitol, esculin, inulin. Oxidaze reaction is negative. The optimum temperature of growth is 25-28°C, maximum 36-37°C, minimum 2°C and lower. Pathogen remains in infected seeds and vegetation residues; it quickly perishes in ground.


Basal Bacteriosis of wheat meets in the USA, Canada, South Australia, and in countries of Southern Africa. The disease is distributed everywhere in the territories of former Soviet Union where wheat is growing; i.e., in the Central Black-Earth zone of Russia (Voronezh, Kursk, Belgorod, Tambov, Lipetsk, Orlov Regions), in the Krasnodar and Stavropol Territories, in the Leningrad, Ivavov, Tver, Rostov, Moscow, Kirov, Volgograd, Saratov, and other Regions, in Western Siberia, Kabardino-Balkaria and North Ossetia, and also in Odessa, Mykolayiv, Kirovohrad, Cherkasy, Kiev, and other Regions of Ukraine, in Minsk, Mahilyow, and other Regions of Belarus, in Kazakhstan.


Basal Bacteriosis actively develops in cool and damp years, particularly during cold, damp spring. Its distribution is promoted by low monthly average temperature (15-18°C) during the beginning of earing before maturing, and increased air humidity (60-65% and more) and excessive precipitations just before grain ripening. Optimum temperature for the Basal Bacteriosis development is 23-25°C.

Economic significance.

In nature, the pathogen of Basal Bacteriosis of wheat attacks also rye, barley, and oats. Depending on a zone of wheat cultivation and weather conditions favorable for the bacteriosis development, this disease can infect 10-80% of ears of wheat plants during epiphytotics. In regions of the Central Black-Earth zone, the Basal Bacteriosis severity changes from 1 to 30-50% (at development 0.3 to 25.3%), depending on a variety of spring wheat and conditions of cultivation; some varieties of winter wheat (Voronezh and Lipetsk regions) can be infected by 72%. In Krasnodar Territory, about 36% of plants are struck by this disease at its distribution 50 to 100%. Control measures include optimal agriculture, maintenance of crop rotation, cultivation of relatively resistant varieties, careful removal of plant residues, separating seeds from shrunken grains, pesticide treatment of seeds before sowing, and treatment of plants by pesticides during vegetation period.

Reference citations:

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Ilyukhina M.K. 1976a. Bacterioses of winter wheat in the Central Black Earth atrip and Krasnodar tarritory and thesubstantiation of measures of its control. PhD Thesis. Moscow: UNIIZR, 18 p. (in Russian).
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Vzorov V.I. 1938a. Elucidation of specific structure and geography of bacterioses of plants in the Soviet Union. In: Kasichin A.N. & Villevalde U.M., eds. Summary of VIZR research works for 1936, Part III. Viruses and bacterioses of plants, a biological method, chemical method and mechanization of plant protection. Leningrad: Gosudarstvennoe izhdatelstvo sovkhoznoi i kolkhoznoi literatuty, p. 40-45 (in Russian).
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