Composition and phytopathogenic properties of bacteria isolated from Pinus sibirica Du Tour wood affected by bacterial wetwood in the Baikal region

Abstract

Currently, in the dark coniferous forests of the Baikal region, the spread of the disease bacterial wetwood disease is noted, causing the sanitary condition deterioration in the forest stands, and leading to the forest dieback on large territories. Despite the fact that this disease has been known since the beginning of the last century, the question of its’ real pathogen is still open. It is believed that associations of various endophytic microorganisms may take part in the development of pathogenesis. In this regard, it seems relevant to study the composition of the endophytic complex of microorganisms in wood with bacterial wetwood of forest species in order to establish the types of relationships between endophytes and test their ability to initiate a pathological process in conifers. An attempt was made to identify the main endophytic microbiome representatives of the «wet wood» of Siberian stone pine (Pinus sibirica Du Tour) affected by bacterial wetwood, to assess their phytopathogenic properties and types of relationships between them. The features of the endophytic microbiome of the Siberian stone pine affected by bacterial wetwood in the Slyudyanskoye forestry of the Irkutsk region were studied. With standard microbiological and phytopathological methods we isolated pure cultures of bacteria and studied their characteristics (including virulence). For bacterias identification molecular genetic methods were used. From the infested wood of Siberian stone pine trees affected by bacterial wetwood, a complex of pure microorganisms cultures, not previously described in other studies, was isolated. Among them, opportunistic strains include Rouxiella chamberiensis, Ewingella americana, Stenotrophomonas rhizophila and Bacillus pumilus, which exhibit pronounced virulent properties in relation to indicator plants and ambiguously affect the growth and development of Scotch pine (Pinus sylvestris L.) seedlings. Mutual impacts of bacteria on each other were noted in the endophytic microbiome of the affected Siberian stone pine wood. Bacillus bacteria showed pronounced antagonistic properties. Basically, in the endophytic community symbiotic relationships were dominated with possible syntrophic connections.

Keywords

• conifer diseases
• bacterial wetwood
• siberian stone pine
• prokaryotic microbiome
• scots pine seeds and seedlings
• virulence of strains
• hypersensitivity reaction