Diseases

Agrobacterium tumefaciens (Smith & Townsend) Conn - Crown Gall of Fruit Cultures.

Systematic position.

Kingdom Procaryotae, section Gram-negative aerobic rods and cocci, family Rhizobiaceae, genus Agrobacterium.

Synonyms.

Agrobacterium radiobacter var. tumefaciens (Smith & Townsend) Keane, Kerr & New, A. radiobacter pv. tumefaciens (Smith & Townsend) Kerr,Young & Panagopolos, Bacillus radiobacter var. tumefaciens (Smith & Townsend) Israilsky, B. ampelopsorae Trevisan, Bacterium tumefaciens Smith & Townsend, Pseudomonas radiobacter var. tumefaciens (Smith & Townsend) Duggar, Phytomonas tumefaciens (Smith & Townsend) Bergey et al.

Biological group.

Hemibiotroph.

Morphology and biology.

Typical symptoms of this bacteriosis lesion are the knogs locatinged mainly on the root neck of the diseased plants, but they can develop on other parts of the roots and less often on trunks (grapevine). The pathogen is a typical wound parasite. Unlike other agents of bacterial diseases, it does not kill plant cells; on the contrary, it stimulates them to irregular division, (due to action of a certain plasmid). In the first phase of the bacteriosis development, the small soft white knogs quickly expand, then later they darken and become knobby and firm. Sometimes they collapse completely, but the following year they appear on the same place. In certain cases, they appear on only part of the plant while the rest of the plant continues to grow. By the end of grapevine vegetation period, the young knogs reach 3.5-7 cm in diameter, being able to reach 8-12 cm and or more on 3-4 -year old apple trees. Frequently the knogs cover the entire stem or shoot of grapevine, deforming them completely. Cells of A. tumefaciens are bacilli, usually 0.6-1.0 x 1.5-3 mkm. Moving by means of 1-3 peritrichous flagella. Gram-negative, not sporing. Aerobes. On potato agar, colonies are convex, watery-brilliant, light-beige, with even transparent margin. The pathogen growth on mediums with carbohydrates is accompanied by plentiful formation of extracellular polysaccharide slime. It is not hydrolyzing starch. Curtailing milk, but not peptonizing. Acidifying litmus milk. Reducing nitrates. Not diluting gelatin or diluting it very slowly. Catalase, oxidase and urease reactions are positive as a rule. Excreting indole, H₂S and NH₃. Forming an acid on saccharose, dextrose, lactose, fructose, lactose, arabinose, galactose, mannitol. The pathogen grows at 0-37°C, optimum temperature for its growth is 25-30°C, maximum 37°C; thermal point of its destruction in plants is 51°C. Optimum range of pH is 6.0-9.0. This pathogen can remain viable in the ground for a long time. An entrance gate for the bacterial infection is injuries being caused by various factors, such as insects, pruning and inoculation.

Distribution.

This bacteriosis has a wide distribution in most countries of the world. It is present in all territories of the former USSR where fruit cultures are growing.

Ecology.

Though knogs can appear during all vegetation of fruit plants, their strongest growth is observed in June and July as their strengthened growth is promoted by high air temperatures and abundant precipitation. The most intensive growth of knogs occurs at temperature 30-35°C and relative air humidity 95%. The bacteriosis causes the greatest harm to vines in the countries with a severe climate for the viniculture. Low negative temperatures and sharp fluctuations during plant hibernation, especially for grapes, cause the appearance of cracks on the bodies of fruit plants which entails the pathogen introduction there and formation of knogs.

Economic significance.

The pathogen is capable of attacking more than 1000 species of the higher plants from 142 genera of 61 families in all areas where grown. The bacteriosis meets on fruit (apple, pear, sweet cherry, peach, cherry plum, plum, cherry) and forest (willow, birch, poplar) species, on grape, berry plantations (currant), industrial (oleander, cotton, horse beans) and flower-ornamental (chrysanthemum, rose) cultures. Apple, pear and grape show especially high susceptibility. The formed knogs do not result in fast destruction of plants. However, the pathogen suppresses their general growth and viability and reduces their resistance to fungi and other infections. It considerably reduces yield, especially the yield in grapes. After a time, the energy of plants is exhausted, and they gradually dry out and finally perish. Within three years, the annual rate of dying grapes exceeds 10% on infected soils. The losses in some varieties exceeded 90% of plants in the Odessa Region of Ukraine. (the Odessa Region). The number of the diseased grape plants increased from 12.4 to 44.5% in Moldova. Depending on weather conditions of vegetation and on resistance of a variety, in Armenia, the lesion of grapevine varied from 7.7 to 33.5%, depending on weather conditions of vegetation and resistance of a variety; (at the development rate 3.7-24.1%) and in some fields to 46-89.3% (at the disease development 65.2%). In conditions of the South of Ukraine, in some years the amount of infected trees of sweet cherry and pear with lesions of root neck reached 28.6-40%, and those with knogs on the main root reached 38.5-62.5%. The lesion of grapevines in some years made 3.5-38.4% in Azerbaijan (depending on variety susceptibility and cultivation zone). The amount of sweet cherry trees (susceptible varieties) with the Crown Gall exceeded 95% under favorable conditions for the pathogen development. In Moldova, the affection of young apple planting reached 58.8% and that of stone-fruits was 11.2%. Control measures include checking ground for contamination by the Crown Gall at fruit nursery layings, application of highly resistant varieties of agricultural crops, preparation of cuttings from healthy trees and bushes (for inoculation), treatment of these cuttings by stabilized bacteriophages, obligatory disinfection of tool (before pruning and inoculation), pruning and burning of the diseased parts of plants, and control of soil pests.

Reference citations:

Babayan A.A., Oganesyan A.A., Nagapetyan Zh.A. 1977. The bacterial cancer of grapevine in the Northeast zone of Armenia and measures of its control. In: Gorlenko M.V., ed. Bacterial diseases of plants. Moscow: Kolos, p. 85-93 (in Russian).
Gorlenko M.V. 1966. The bacterial of diseases of plants. In: Sokolova N.A., ed. Moscow: Vysshaya shkola, 291 p. (in Russian).
Isaeva E.V. 1966. Control measures against root cancer of fruit cultures. In: Bel.tyukova K.I., ed. All-Union symposium on bacterial diseases of plants (Abstracts of reports). Kiev: Naukova dumka, p. 31-32 (in Russian).
Kiryukhina R.I., ed. 1981. Methodical recommendations on diagnostics of bacterial cancer of grapes. Moscow: VASKHNIL, 20 p. (in Russian).
Kuz.michev A.A., ed. 1976. Measures of struggle against bacterial cancer of grapes. Methodical recommendations. Moscow: VASKHNIL, 6 p. (in Russian).
Mager M.K. 1980. Studying the reasons of damage of fruit cultures by bacterial (root) cancer in Moldova. In: Kiryukhina R.I., ed. Condition and prospects of development of scientific researches on prevention of resistance of pests and pathogens of diseases to pesticides and development of effectual measures of struggle against bacterial diseases of plants (Abstracts of reports of IV meeting). Moscow: VASKHNIL, p. 112-113 (in Russian).
Makrushina A.T. 1977. Bacterial cancer on grape plantings. In: Gorlenko M.V., ed. Bacterial diseases of plants. Moscow: Kolos, p. 80-85 (in Russian).
Mamedov A.H. 1975. Bacterial cancer of grapevine. In: Zatula D.G., ed. Phytopathogenic bacteria. Kiev: Naukova dumka, p. 282-283 (in Russian).
Mamedov A.H. 1976. The use of microbes - antagonists and antibiotics in struggle against bacterial cancer of grapevine. In: Kanchaveli L.A. et al., eds. III All-Union conference on bacterial diseases of plants (Abstracts of reports). Tbilisi: Metsniereba, p. 153-155 (in Russian).
Myalona L.A. 1990. Root cancer of fruit cultures in conditions of the South of Ukraine and measure of its control. In: Gvozdyak R.I., ed. Materials of conference. Phytoncides. Bacterial diseases of plants. Part 2. Kiev & Lvov: KGT-2, p. 129-130 (in Russian).
Nagapetyan Zh.A. 1975. To studying cancer of grapevine in the Northeast zone of Armenian SSR. In: Zatula D.G., ed. Phytopathogenic bacteria. Kiev: Naukova dumka, p. 276-278 (in Russian).
Nagapetyan Zh.A., Kazaryan L.V. 1980. The lesion of Ararat Plain vineyards by bacterial cancer. In: Kiryukhina R.I., ed. Condition and prospects of development of scientific researches on prevention of resistance of pests and pathogens of diseases to pesticides and development of effectual measures of struggle against bacterial diseases of plants (Abstracts of reports of IV meeting). Moscow: VASKHNIL, p. 122-123 (in Russian).
Palavandishvili I.V., Tsilosani G.A. 1976. Results of studying bacterial cancer of grapevine in Georgia and measures of its control. In: Kanchaveli L.A. et al., eds. III All-Union conference on bacterial diseases of plants (Abstracts of reports). Tbilisi: Metsniereba, p. 156-157 (in Russian).
Panfilov L.G. 1980. Bacterial cancer of grapes in Crimea and prospects of researches on its control. In: Kiryukhina R.I., ed. Condition and prospects of development of scientific researches on prevention of resistance of pests and pathogens of diseases to pesticides and development of effectual measures of struggle against bacterial diseases of plants (Abstracts of reports of IV meeting). Moscow: VASKHNIL, p. 123-124 (in Russian).
Shpaar, D, Kleinkhempel, G, Myuller, G. & Naumann, K. 1980. Bacterioses of cultural plants. Handbook. Moscow: Kolos, p. 111-112 (in Russian).

© Lazarev A.M.

Photo is taken from the Archive of documentary photographs of the Institute of Phytopathology and Plant Protection at University of Goettingen (Germany) and is published with the kind permission of Prof. Dr. K. Naumann (Germany).