Plant growth promoting and antagonistic properties of endophytic bacteria isolated from domestic apple@@@Naminės obels endofitinių bakterijų izoliatų augalų augimą skatinančios ir antagonistinės savybės

Bacterial endophytes are common inhabitants of plant tissues that have been shown to play an important role in regulation of plant growth and to have the potential as biological agent for plant disease protection. Only fragmented knowledge is present about endophytes that reside in the phyllosphere of cultivated tree plants such as domestic apple (Malus x domestica Borkh.). Therefore the goal of this study was to identify culturable endophytic bacteria characteristic of an apple phyllosphere and to establish biochemical traits involved in plant growth promoting activity as well as to study microbial growth suppressing activity of the endophytes. Thirty-eight putative endophytic bacteria were isolated from apple buds of cultivars 'Gala', 'Golden Delicious' and 'Orlovim' grown under field conditions and 13 of the isolates were assigned to Curtobacterium, Pantoea and Pseudomonas species. Biochemical tests revealed traits important for plant growth stimulation and microbial growth suppression characteristics of the isolates, including nitrogen fixation, production of indole-3-acetic acid (IAA), phosphate solubilization, production of siderophores and hydrogen cyanide. Several isolates displayed antagonistic activity against selected non-pathogenic and pathogenic bacterial strains: 17 isolates were able to inhibit growth of Micrococcus luteus, 4 - Pseudomonas aeruginosa, 2 - Escherichia coli and Bacillus subtilis. In addition, it was determined that two isolates of Pantoea sp. (D_8 and D_10) and Pseudomonas fluorescens group isolate D_7 were able to inhibit growth of the apple scab pathogen (Venturia inaequalis (Cke) Wint.), suggesting a role of the endophytes in disease resistance and a potential use for biocontrol applications.