Institute of Microbiology and Virology of the National Academy of Sciences, Zabolotny Street 154, 252143 Kyiv, Ukraine

Background and objectives
Among the plant pathogens the main and the most widespread in Ukraine are the agents of bacterial diseases of cereals from the genus Pseudomonas. It has been established that these agents can be founded in epiphytic phase on healthy host plants. The purpose of our research was to isolate phytopathogenic bacteria of the genus Pseudomonas from healthy plants of rye, oats and weeds and to study their biological properties in order to reveal distinctions from other bacteria isolated from affected plants.

Materials and methods
Bacteria, isolated from healthy plants of rye, oats and weeds, growing in oats field were studied. Physiological and biochemical properties of the bacteria were studied by commonly used methods and identified according to [1]. The pathogenic properties were tested under field conditions on the rye and oat plants. The degree of disease development was estimated by using 4-point scales [2]. Serotyping was carried out according to the scheme of Pastushenko and Simonovich [3].

Results and conclusions
The isolates from healthy plants of rye were identified as Pseudomonas syringae pv. atrofaciens (P.s.a.) , and those from oats and weeds (coltsfoot, dandelion, amarant, saltbush, camomile ) as P. ;syringae pv. coronafaciens (P.s.c.). Bacterial epiphytes did not differ in physiological and biochemical properties from bacteria, isolated from infected plants. The strains studied were pathogenic (1-3 on aggressiveness scale), and differed in this aspect from highly aggressive strains from the affected plants. Serological researches have shown, that the strains of P.s.c., isolated from healthy plants of oats are homogenic. According to the presence of group-specific antigen complexes they were referred to serogroup 1 using the scheme of Pastushenko and Simonovich [3]. P.s.c. strains from infected plants were divided into two serogroups, I and V. Strains belonging to serogroup V were dominant. Strains of P.s.c. from weeds were heterogeneous in antigenic properties and belonged to two serogroups, I and 11. Some strains had weak serological relationship with representatives of nine known serological groups of P. ;syringae pathovars and did not belong to them. Strains of P.s.a. from healthy plants of rye belonged to serogroups II and VI. Strains of P.s.a. from infected plants were included in five serogroups: I, II, IV, V and VI. The majority of strains (50%) belonged to serogroup I. Thus, it was shown, that the strains of P.s.a. and P.s.c., isolated as epiphytes differed in antigenic properties from strains obtained from affected plants.

1. Bergey's Manual of Systematic Bacteriology, 9th edn, 1984, Vol. 1.
2. Peresypkin VF, Koroleva IB, Minko ND, 1978. Doklady Vaschnil 6, 11 (in Russian).
3. Pastushenko LT, Simonovich ID, 1979. Mikrobiologichnii Zhurnal 41, 330-339 (in Russian).