Etiology of bacterial wetwood of Quercus robur L.

Phytopathogenic bacteria in the plant organism form an integral part of the accompanying microflora, as well as pathogens of pathological processes that do not just weaken the plant, but shortly (with acute pathogenesis) lead to degradation and complete dieback. Notably, bacteriosis is described by typical macroscopic signs of the course of the disease, but the exact aetiology of the pathological process can be reliably established only based on bacteriological analysis with the identification of morphological, cultural, and biochemical properties of isolates. The purpose of this study is to experimentally confirm the direct causes of oak degradation caused by bacterial wetwood in the tree stands under study, as well as to investigate the morphological and biochemical properties of the pathogen. This study employed classical microbiological, phytopathological, and biochemical methods that establish the aetiology of the disease, analyse typical symptoms, include microscopy of the affected parts of the oak, isolation, and identification of the pathogen. The properties of bacterial isolates were figured out according to generally accepted methods and using the API 20E test system and the NEFERMtest24 MikroLaTEST®, ErbaLachema a test system. It was experimentally confirmed that by all macroscopic signs (crown openness, exudate discharge from bark cracks, presence of depressed (sunken) necrotic wet wounds in certain areas of cracks, development of a wet pathological core, presence of epicormic sprouts, etc.) the identified disease is a systemic, vascular-parenchymal bacteriosis, known as bacterial wetwood of common oak. The isolated bacterial isolates were identified by morphological, physiological, and biochemical properties as Lelliottia nimipressuralis – the causative agent of bacterial wetwood of common oak. This suggests that the aetiology of degradation of common oak in Ukraine is closely related to bacteriosis, and the results of this study allow for early phytosanitary diagnostics of the state of common oak in natural conditions based on typical symptomatic signs