A bacterial isolate called 49M, showing protective activity against fire blight caused by the bacterium Erwinia amylovora, was selected from a large collection of isolates obtained from the apple phyllosphere and was identified as Pseudomonas graminis, based on its phenotype and sequence analysis of the 16S rRNA and rpoD genes. The efficacy of strain 49M under laboratory and greenhouse conditions to protect apple blossoms and apple terminal shoots was equal or even higher than that of the reference strains A506 of Pseudomonas fluorescens and C9-1 of Pantoea vagans, as well as the bioproducts BlightBan A506, Blossom Protect and Hortocyna 18 SP (streptomycin), used for comparison. However, its activity on pear fruitlets was slightly less effective, but significantly better (over 10 %) than that of BlightBan A506. When strain 49M was introduced onto apple blossoms in orchards, it effectively colonised them during the entire bloom period, in different weather conditions, including rain. The strain showed no pathogenicity towards plant tissue (pear fruitlets, apple blossoms, tobacco leaves) and is therefore, a potential candidate for the development of a new biopesticide against fire blight.

The aim of these studies was to develop an effective formulation for microbial strains active in plant protection. Emulsification technique in oil was used to produce alginate microcapsules supplemented with organic additives to improve production process and stability of the preparations during storage. The release of microorganisms from the capsules in soil and their effectiveness in biocontrol of Fusarium wilt were evaluated. Three bacterial strains Burkholderia cepacia strain CAT5, Bacillus spp. strains PZ9 and SZ61, and fungus Trichoderma virens TRS106 were immobilized separately in calcium alginate supplemented with chitosan, peat powder, or skim milk. The productivity of microcapsules was enhanced by 60% when peat was added to the alginate matrix. Peat reduced also contamination of the capsules during storage, significantly enhancing their quality. By contrast, the addition of skim milk reduced quality of the microcapsules. The additives did not influence the viability of entrapped microorganisms and their release in soil. The survival of the microbial cells was mainly related to the kind of microorganism used, and the highest viability showed Bacillus sp. PZ9 and Trichoderma TRS106. Lyophilization of the microcapsules appeared to be unfavorable by reducing microbial viability in the capsules and in the soil after application. The best properties: good storage ability and sufficient microbial release in the soil, exhibited wet microcapsules amended with peat. These capsules were used to control Fusarium wilt in tomato plants. The protective effect was obtained when the microcapsule-entrapped bacteria PZ9 were used. The effectiveness of this bacterium was comparable with fungicide. Peat-amended microcapsules entrapping Bacillus PZ9 showed the best quality and may have potential for commercial use.