The mycological study of conifers in Tbilisi and its surroundings

Abstract

Extensive microbiological research was carried out in Tbilisi (capital of Georgia) and its surroundings to determine the causes of massive disease and dieback of urban coniferous plantations. The biological material was picked up in June-July 2020 from trees with various degrees of the disease in 42 different localities. 247 conifers (15 species) were examined microbiologically. 1 169 samples of microscopic fungi were isolated. Based on cultural-morphological and molecular-genetic (PCR) studies, 34 strains were identified to the species level, 17 to the genus level, and 1 strain to the family level. Ascomycota were represented by 15 families and 33 species, Basidiomycota by 1 family and 2 species and Zygomycota by 2 families and 2 species. Among the isolated strains, 9 species were clearly dominant and found in all studied coniferous species: Alternaria alternata (Fr.) Keissl, Sphaeropsis sapinea (Fr.) Dyko & B. Button, Epicoccum nigrum Link., Sordaria lappae Potebnia, Curvularia spp., Dothiorella spp, Nothophoma quercina (Sydow & P. Sydow) Q. Chen & L. Cai, Phoma odoratissimi Q. Chen, Didymella aliena (Fries) Q. Chen & L. Cai. It may be supposed that massive activation of pathogenic fungi is the result of weakening of plant immunity on the background of increasing abiotic stresses in Tbilisi over the years; which led to an imbalance between latent pathogens and host plants and eventually to the depressing consequences of trees dieback.