Characterization and population diversity of Erwinia amylovora strains originating from pome fruits in Serbia

Abstract

The diversity of 30 Erwinia amylovora strains, isolated from quince, pear and apple trees on 14 localities in Serbia, was studied using bacteriological and molecular methods. In pathogenicity tests, all strains caused necrosis and oozing of bacterial exudate on inoculated immature pear, cherry and plum fruits, and induced hypersensitive reaction in tobacco leaves. The studied strains were Gram and oxidase negative, non-fluorescent, levan and catalase positive and facultatively anaerobic. The strains did not reduce nitrates, but utilized citrate and produced acid from sorbitol, hydrolyzed gelatine, produced reducing substances from sucrose and grew in the presence of 5% NaCl, but not at 36oC. Identity of the strains was confirmed by conventional and nested PCR methods. Rep-PCR with REP, ERIC and BOX primers resulted in amplification of several DNA fragments respectively, but showed no variation within the strains. However, different genetic profiles were obtained with RAPD-PCR by using six primers which enabled differentiation of the strains into four groups. Genetic differences between the studied strains did not correlate with the host plants, geographical origin or year of isolation.

Primenom standardnih bakterioloških i molekularnih metoda proučen je diverzitet 30 sojeva Erwinia amylovora izolovanih iz dunje, kruške i jabuke, poreklom iz 14 lokaliteta u Srbiji. Svi proučavani sojevi izazvali su nekrozu i pojavu bakterijskog eksudata na nesazrelim plodovima kruške, trešnje i šljive, kao i hipersenzitivnu reakciju duvana. Proučavani sojevi bili su Gram i oksidaza negativni, fakultativno anaerobni, levan i katalaza pozitivni i nisu stvarali fluorescentni pigment na Kingovoj podlozi B. Svi sojevi hidrolizuju želatin, koriste citrate i stvaraju kiselinu iz sorbitola, proizvode redukujuće supstance iz saharoze, ne redukuju nitrate, razvijaju se u prisustvu 5% NaCl, ali ne i pri 36°C. Identitet sojeva potvrđen je konvencionalnim PCR i nested PCR metodama. Rep-PCR metodom korišćenjem REP, ERIC i BOX prajmera umnoženo je više fragmenata DNK čiji broj i veličina su se podudarali kod svih proučavanih sojeva. Za razliku od Rep-PCR, primenom RAPD-PCR metode uz korišćenje šest prajmera došlo je do izdvajanja različitih genetičkih profila i diferencijacije sojeva u četiri grupe. Genetičke razlike među proučavanim sojevima nisu bile u korelaciji sa domaćinima iz kojih su izolovani, niti sa njihovim geografskim poreklom i godinom izolacije.