Bacterial wetwood of silver birch (Betula pendula roth): symptomology, etiology and pathogenesis

Abstract

The article is focused on microbiological and silvicultural properties of bacterial wetwood of silver birch (Betula pendula), also known as European white birch. During the active phase of the disease, bacterial wetwood (i.e. bacterial dropsy, vascular parenchymatous bacteriosis or flux slime) is characterised by crust and periderm bloating, necrotic wet stains and abundance of exudate. The disease is more likely to occur in older (r = 0.56, p < 0.01) and less-dense (r = −0.29, p < 0.01) stands.The statistical model showed that the chance of bacterial wetwood increases with birch age by 0.36% per year. The stands with birch proportion of over 70% demonstrated 15.3% lower infection rate compared to the stands with lower birch presence. The stands with lower stocking demonstrated a higher proportion of infected tree distribution by 7.5% compared to the stands with higher birch representation. The most vulnerable were larger, older B. pendula trees with longitudinally fissured bark that grow on poorer soils and experience frequent water stress.Birch associations with Pteridium aquilinum and Vaccinium myrtillus were more susceptible to infection (31.6% and 44.3%, respectively), whereas associations with Brachypodium sylvaticum, Sphagnum palustre and Calluna vulgaris were at lower risk. Strong ecological and trophic association of bacterial wetwood was present between silver birch and Tremex spp., particularly Tremex fuscicornis. Mycobiota was represented by Rhizopus microsporus, Mucor mucedo, Penicillium aurantiogriseum, Penicillium purpurogenum and Acremonium strictum.Enterobacter, Xanthomonas, Pantoea and Bacillus spp. associated with bacterial wetwood of silver birch were isolated. Enterobacter nimipressuralis was found to be the primary causative agent through means of artificial infection, while other bacteria were found to be either weak pathogens or concomitant. E. nimipressuralis formed the largest number of colony-forming units (CFU) for bark and cambium (164 and 127 CFU, respectively) and was also found in a small amount as a vital obligate in the automicrobiota in healthy birch trees.

Myco- and microorganisms in the tuberculosis pathology of the common ash in Ukraine and interaction between them

“…Under natural conditions, the interaction in the systems "bacterium-bacterium", "bacterium-micromycete", "micromycete-bacterium" can and obviously should be different, because the micro-and microorganisms are influenced by various factors (woody plant at certain stages growth and development, its physiological state, the presence of a pathology, meteorological (synoptic) factors, including as catalysts of pathology, compliance of forest woody plant with forest conditions, etc.). However, experiments with coniferous forest woody plants have shown that phytopathogenic bacteria (so-called vital obligates) in natural conditions outside the pathological process do not affect the growth of micromycetes (Gvozdyak, 2005;Goychuk, 2020b). Studies of biological products ("Victant" and "P27ant") based on aerobic spore-forming bacteria Bacillus sp.…”

Ecological and forestry essence of bacteriosi of forest woody plants in the forests of the Forest-Steppe and Polissya of Ukraine

“…In recent decades there has been epiphytotic dieback of the birch associated with vascular parenchymal bacteriosis, which has different names (bacterial dropsy, bacterial wet cancer, brown slime, watermark disease, "crying" of birch, "wetwood", "Slime flux", "alcoholic flux", etc., but a common etiology and pathogenesis. The causative agent of the bacterial dropsy of the birch in Ukraine is the polybiotroph Enterobacter nimipressuralis, the pathogenicity of which is proved in the experiment both during spring and autumn inoculation of experimental plants [2].…”

“…Currently, bacteriosis and their pathogens are largely studied for plants of agrocenosis. As for the bacteriosis of forest trees, they have not been studied sufficiently, although in recent decades increased attention has been paid to this problem [1,2,3,4]. It is emphasized that on forest trees in the world several dozens of bacteriosis with different degrees of damage caused by bacteria of genera Pseudomonas, Xanthomonas, Enterobacter, Erwinia, Agrobacterium, Brenneria, Xylella, Rhizobium, Corynebacterium, Bacillus, Clostridium etc.…”

“…In the pathology of bacterial dropsy, in addition to E. nimipressuralis, have been identified Xanthomonas campestris, Pantoea agglomerans associated with disease (showed variable pathogenic properties indicating a possible extension of the range of nutritional plants for the mentioned bacteria), Bacillus subtilis and micromycetes from the Zygomycota, Ascomicota, Deuteromycota divisions [2].…”

Lelliottia nimipressuralis (Carter 1945) Brady et al. 2013 – the Causative Agent of Bacterial Dropsy of Common Oak (Quercus robur L.) in Ukraine

“…In 1952, he pointed out that the following bacterial species were isolated from various damage to oak in the forests of Ploiesti: Erwinia valachica Georg et Bod, Erwinia valachica f. onaca, Erwinia gueieicola Georg, et Bod. [26].…”