Fire blight disease caused by Erwinia amylovora can infect almost 140 plants of the Rosaceae family and poses a great threat to pome fruits growing all over the world. It needs amylovoran and Type III secretion systems (T3SS) to cause disease in host plants. AmsB, AmsD, AmsE, AmsF, AmsG, AmsJ, AmsI and AmsK proteins are involved in the binding of different galactose, glucuronic acid and pyruvyl subunits to the lipid carrier to form an amylovoran unit. T3SS proteins secreted by E. amylovora are HrpA HrpN, HrpW, AvrRpt2EA, HopC1 and DspA/E. DspA/E, the sole effector of E. amylovora, is secreted by during the formation of pilus T3SS. The chaperone protein of E. amylovora is DsB/F, which is in the IA class. EopB (outer membrane protein) has been characterized as one of the secretory proteins of E. amylovora. In addition to the harpins, the pathogenicity protein DspE and OrfB proteins are secreted via the Hrp-secretory system of E. amylovora. E. amylovora forms a Hrp pilus, which is produced by the structural protein HrpA. Genes encoding antimicrobial proteins cloned and expressed in apples and pears for impart resistance to the pathogen, attacin E are cecropins and lysozymes. The expression of PR2, PR5 and PR8 proteins is increased with E. amylovora infection in apple. Again, the HIPM protein in apples interacts with the E. amylovora HrpN protein, and the HIPM protein is found in higher amounts in flowers than leaves and shoots. In addition, four apple proteins (DIPMs) that interact with E. amylovora effector protein DspA/E have an effective role in endurance. In order to understand the interaction between the plant and the pathogen, it will be possible to understand the proteins that recognize the pathogen in the host, as well as the signal system and plant defense mechanism resulting from the infection. In this study, the roles of proteins associated with pathogenesis as a result of infection of E. amylovora in apples were tried to be revealed.

Fire blight disease caused by Erwinia amylovora is a destructive bacterial pathogen mainly on pears, apples and quinces from Rosaceae family. In this study, it was aimed determination of total protein amounts in different apple cultivars (Braeburn, Fuji, Gala and Golden), pear cultivars (Santa Maria and Williams) and quince cultivars (Eşme and Ekmek) in the infections of two virulent E. amylovora strains (Ea234-1 and Ea240-3) according as the time. It was taken leaf samples after leaf inoculation with E. amylovora (108 CFU ml-1) at 24th, 36th and 72nd hours. For verification of the infections, re-isolations were made from bacteria inoculated plants and the agent was identified as E. amylovora by biochemical, physiological and molecular tests. In determining the amounts of total protein and in the SDS-PAGE analyses were used Bradford and Laemmli methods, respectively, and absorbance values of protein extracts derived from the leaf samples taken, were obtained at 595 nm wavelength. According to the findings obtained; after infection of E. amylovora in the apple varieties comparing to controls, total protein concentrations at 24th hours increased and a decrease in the amount of 36th to 72nd hours and Braeburn has the highest protein content was determined. In the pear varieties, while total protein concentrations at 24th and 36th hours increased, a decrease in the amount of 72nd hour, and Santa Maria variety has the highest protein content was detected. In the quince varieties, total protein concentrations at 72th hour increased and Eşme variety has the highest protein content was identified. As a result of SDS-PAGE analysis, protein fractions which have different molecular weights were obtained. The protein bands were defined approximately 55-70 kDa and 35-55 kDa molecule weight on apple and quince varieties, respectively and also approx. 55-70 kDa in pear varieties.

Fire blight, affecting more than one hundred and thirty species in the Rosaceae, is probably the most destructive disease affecting pear and apple cultivars in many countries. Currently, there are no effective synthetic compounds with systemic properties. Other major problem is the occurrence and spread of strains of Erwinia amylovora with resistance to streptomycin and copper. Taken into consideration the human and environmental health, the use of biocontrol agents either as an alternative or as a supplement within an integrated fire blight management strategy has attracted worldwide attention. In this study, E. amylovora solution of 107 CFU ml-1 was treated with bio-control agents, Bacillus subtilis str. QST 713, B. amyloliquefaciens str. MBI 600 and their mixture (at solution densities of 106, 107 and 108 CFU ml-1 for each one) on Petri dishes, containing King’s B medium and, compared with positive (streptomycin sulphate) and negative (sterile distilled water) controls. In vivo studies were performed on two-year-old apple cv. Gala seedlings grown in 45-cm-diameter pots containing a sterilized mix of soil–sand–peat under controlled greenhouse conditions (85% relative humidity, 25°C temperature and 16h of day light). The plants were irrigated as needed by drip-irrigation and each pot received a mineral solution (NPK: 20–20–20) at 2 g l-1 twice. When plant shoots reached a length of 30-35 cm, bio-control agents, individually and their mixture, were applied to the plants by a hand-sprayer. Obtaining the data, 108 CFU ml-1 of Bacillus spp. suspension mixture showed strongest in vitro antibacterial effect (26mm) among the tested treatments after positive control streptomycin (28.6mm). Parallel to in vitro findings, the mixture was most effective against the pathogen on cv. Gala (66.03%). Findings show that the use of mixture of beneficial microorganisms with individual antagonistic properties against the pathogen can be an effective strategy as a natural alternative to agrochemicals in the scope of good agriculture practices.