Fungal And Bacterial Communities In Healthy And Canker-infected Bark Of Populus×euramericana Cv.’74/76’and P.×euramericana Cv.’zhonglin46’

Poplar trees, deciduous plants, are part of the Salicaceae family, widespread in Europe, Asia, North America, and is one of the world’s most widely distributed and most adaptable tree species. Populus x euramericana cv.’74/76’was wildly cultivated in the north China plain in recent years, and was planted more than hundreds of thousands of acres in Puyang, Henan province. A new canker desease was observed from P. xeuramericana cv.’74/76’and P. x euramericana cv.’zhonglin46’, which threats the cultivation of those cultivars. How to effectively control the diseases has become urgent problem needed to be solved, the disease prevention and control using plant endophytes has become a possible approach.In order to understand predominant species dynamic and diversity of fungal and bacterial endophytes in barks of Populus x euramericana, fungal and bacterial endophytes were isolated from barks of P. x euramericana cv.’74/76’and P. x euramericana cv.’Zhonglin46,and identified by sequence analysis of the internal transcribed spacer (ITS) and morphological characterization by microscopic observations. The seasonal dynamic analysis of fungal and bacterial endophytes in both cultivars was performed. The cultivable bacteria and fungi from poplar canker bark in Puyang city were isolated, and the dominant population of fungi and bacteria hosted in P. x euroamericana canker was analysed. And the isolates belong to the genus Acinetobacter and Lonsdalea were identified by polyphasic taxonomy. The main results and conclusions are as follows:Fungal endophytes isolated from barks of P. x euramericana cv.’74/76’and P. x euramericana cv.’zhonglin46’were classified into30different fungal taxa belonging to17genera of Ascomycota. The results revealed that there are high phylogenetic diversity of endophytic fungus in the bark of P. x euramericana cv.’74/76’and P.×euramericana cv.’zhonglin46’.Endophytic bacteria strains isolated from barks of P. x euramericana cv.’74/76’and P. x euramericana cv.’zhonglin46’ belong to58species of32genera, including32species of20genera from the barks of P. x euramericana cv.’74/76’ and36taxon of19genera from the barks of P×euramericana cv.’zhonglin46’. Alternaria alternata, Botryosphaeria dothidea, Fusarium spp., Diaporthe spp., were predominant species of fungal endophytes in barks of both cultivars of P.×euramericana while Alternaria alternata and Botryosphaeria dothidea were most common predominant species.Climate factors including temperature and humidity have important effects on the endogenous bacteria composition and dominant population of endophytic microorganism of P×euramericana cv. ’74/76’and P.×euramericana cv."zhonglin46. The results showed that bacterial endophytes diversity index in spring and autuin was higher than that in summer and winter. In the cold season, genus Rhizobium and other beneficial strains become a dominant population, which maybe increase resistance of the tree to the bad weather.In the endophytic bacterial communities of P.×euramericana cv.’74/76’and P.×euramericana cv.’Zhonglin46, there are many kinds of beneficial strains to plant, such as Pseudomonas, Pantoea, Rhizobium, Trichoclerma, which revealed that there are a lot of beneficial and bio-control microbial resources. While, two potential plant pathogens, B. doth idea and F. solani, were isolated from the bark of P.×euramericana cv.’74/76’and P.×euramericana cv."zhonglin46, which are important pathogens to some plants. So, the plants tested in this study have a big risk of the desease occurrence.There are big difference in the microbial communities from healthy and canker-infected P.×euramericana cv.’74/76’and P.×euramericana cv.’Zhonglin46’. The beneficial strains were predominant in the healthy plants bark micro-ecosystem, including Pseudomonas spp., Pantoea spp., Rhizobium spp., Microbacterium spp. and Bacillus spp. While, pathogenic strains, intestinal bacteria and fermentation bacteria arc common species in the descased bark sites. Bacterial dominant population is Lonsdalea quercina subsp. populi in the sites of the bark infected canker, and Fusarium solani is fungal dominant population in the micro-ecosystem of the canker-infected bark. Furthermore, Brenneria salicis, Pectobacterium wasabiae, Pectohacterium carolovorum subsp. carotovorum, Alcaligenes faecalis, Lactobacillus plantarum, Corynehaelerium flavescens and Corynebacterium variubile were also isolated from the diseased bark parts, the relationship between those strains and the causal pathogen of the canker disease needs further study. According to the physiological and biochemical characteristics, genetic type features, five strains isolated from diseased barks, including N-5-1, HZ1031and4-4, were identified as Lonsdalea quercina subsp. populi, a new record species in China. Seven strains belong to genus Acinetobacter were identified as three new species, and strains BQ4-1T and NII13were named Acinetobacter puyangensis sp. nov; strains PBJ7and PZ6named Acinetobactei popli sp. nov, strains2E3J1T, HI’5-2and2C-3-1named Acinetobacter qingfengensis sp. nov...