Bacterial Diseases of Silver Birch (Betula pendula Roth.)

Abstract

A significant role in the pathogenesis of diseases of woody plants belongs to phytopathogenic bacteria and fungi. It has been scientifically confirmed that the organs and tissues of woody plants have a certain myco- and microbiota, the components of which are systematically interconnected both with each other and with the plant. The species composition and quantitative ratio are constantly changing both in the process of ontogenesis of the tree and with changes in its physiology. The aim of the work was to study the species composition and the formation of diversity and systemic interactions of microbiota associated with bacterial dropsy in the pathology of Betula pendula Roth. Methods. Classical microbiological, phytopathological, biochemical, statistical methods were used in the work. Combined diagnostic methods were also used, in particular careful microscopic examination of the affected parts of plants, isolation and identification of the pathogen. Results. Bacterial origin of wet wood in the trunk of birches was detected. Samples of wood and exudate were taken for laboratory studies from plants that had pronounced signs of pathology (cracks, swellings). It has been experimentally proved that the causative agent of bacterial dropsy of silver birch is the phytopathogenic polybiotrophic bacterium Lelliottia nimipressuralis, which causes dropsy of coniferous and deciduous woody plants and experimentally found pathogenic properties to B. pendula. Xanthomonas campestris, Pantoea agglomerans and Bacillus subtilis are associated with bacterial dropsy pathology of B. pendula. The pathogenic properties of P. agglomerans and X. campestris on B. pendula are variable, which indicates the possibility of the expansion of the circle of plants sensitive for these species of bacteria. It was established that L. nimipressuralis both during spring and autumn inoculation showed high pathogenicity to B. pendula. In only one case, on isolated on the border of healthy and affected wood from young B. pendula (bast part) the results of artificial injury were less pronounced. Other bacteria isolated from bacterial dropsy, in particular X. campestris, were non-pathogenic for B. pendula. At the same time, we noted traces of artificial infection with X. campestris in the samples isolated on the border of healthy and affected wood from middle-age B. pendula (cambial part). This may indicate an expansion of the circle of sensitive plants or the increased sensitivity of certain forms of birch for the mentioned bacteria, which is quite likely, since the bacteria have a significant forms variety. In 10 places of inoculation no pathology caused by B. subtilis was found. Bacteria of the Bacillus genus were non-pathogenic for B. pendula in all experiment. Our studies have shown that they can be a regulatory factor in the development of bacterial dropsy. Conclusions. A certain variability of isolated strains in the assimilation of some carbohydrates and alcohols can be explained by the specific conditions of the existence of bacteria, including the influence of environmental factors on their biochemical properties. It is known that the ecological niche affects even the antigenic composition of bacteria; therefore, such an effect should also be expected on other properties. Our studies confirmed that causative agent of bacterial dropsy is L. nimipressuralis and clarified the information about this bacteria cells size.