The impact of three bacteria isolated from contaminated plant cultures on in vitro multiplication and rooting of microshoots of four ornamental plants

The strains of bacteria Paenibacillus glucanolyticus, Curtobacterium pusillum and Methylobacterium extorquens were isolated as non-deleterious contaminations from hosta or raspberry tissue cultures. Microshoots of chrysanthemum, gerbera, hosta and rose were inoculated with these bacteria and their influence on shoot multiplication and rooting was evaluated. None of the investigated bacteria caused symptoms of hypersensitivity or vitropathy on the shoot explants at rooting and shoots multiplication. C. pusillum stimulated axillary shoot formation in all studied plant genotypes. Length and number of rose roots and their length were higher but number of roots and their length in chrysanthemum were lower in inoculated than in controls. The number and the length of shoots and roots in gerbera and hosta and the number of shoots in chrysanthemum inoculated with M. extorquens were higher but shoot length of chrysanthemum and rose, and root length of rose were lower as compared with controls. P. glucanolyticus influenced higher number and length of chrysanthemum shoots and root length of chrysanthemum and gerbera than noninoculated control but the number of gerbera and hosta roots was lower and root length of rose was as low as 0.2 cm. All assessed bacteria were able to assimilate atmospheric nitrogen and M. extorquens and P. glucanolyticus were able to produce IAA.