Diversity and antibacterial activity of fungal endophytes from Eucalyptus exserta

Abstract

Background Eucalyptus bacterial wilt caused by Ralstonia solanacearum is an important eucalyptus disease. Endophytic fungi, an important source of natural active substances, provide a new breakthrough for the control of plant diseases. Results In the present study, 80 endophytic fungal isolates were obtained from the healthy branches and fruits of Eucalyptus exserta. Fifteen distinct isolates (MK120854-MK120868) were selected for further taxonomic identification through morphological trait assessments and internal transcribed spacer (ITS) region-rRNA gene sequence analysis. Thirteen genera, namely, Phyllosticta, Penicillium, Eutypella, Purpureocillium, Talaromyces, Lophiostoma, Cladosporium, Pestalotiopsis, Chaetomium, Fusarium, Gongronella, Scedosporium and Pseudallescheria, were identified on the basis of their morphological characteristics. Members of the genus Phyllosticta were the primary isolates, with a colonization frequency (CF) of 27.5 %. Most of the fungal isolates displayed antibacterial activity. The crude extracts obtained from Lophiostoma sp. Eef-7, Pestalotiopsis sp. Eef-9 and Chaetomium sp. Eef-10 exhibited strong inhibition on the test bacteria, and Lophiostoma sp. Eef-7 was further cultured on a large scale. Three known compounds, scorpinone (1), 5-deoxybostrycoidin (2) and 4-methyl-5,6-dihydro-2 H-pyran-2-one (3), were isolated from the endophytic fungus Lophiostoma sp. Eef-7 associated with E. exserta. The structures of these compounds were elucidated by analysis of 1D and 2D NMR and HR-ESI-MS spectra and a comparison of their spectral data with published values. Compounds 1 and 2 showed weak antimicrobial activity against Ralstonia solanacearum. Conclusions Endophytic fungi from Eucalyptus exserta may represent alternative sources of antimicrobial agents. Lophiostoma sp. Eef-7 can produce 2-azaanthraquinone derivatives and shows weak antibacterial activity against Ralstonia solanacearum.

Fungal Endophytes: A Potential Source of Antibacterial Compounds

“…Eef-7 is associated with Eucalyptus exserta. Compounds 394 and 395 displayed poor antibacterial activity against Ralstonia solanacearum with 9.86 and 9.58 mm zones of inhibition when 64 µg was added (positive control was streptomycin sulfate with a 13.03 mm zone of inhibition at an added amount of 6.25 µg) [171].…”

Ralstonia solanacearum Infection Disturbed the Microbiome Structure Throughout the Whole Tobacco Crop Niche as Well as the Nitrogen Metabolism in Soil

“…It is well known that soil microbes play a vital role in enhancing stress resistance, resisting soil pathogens, and regulating host immunity, and changes in soil physiochemical properties can inversely influence the microbial community of the rhizosphere ( Jones et al, 2009 ; Mendes et al, 2013 ). The increase in endophytic beneficial bacteria of the rhizosphere and plant roots makes pathogen infection more difficult, thus making plants resistant to diseases ( Achari and Raman, 2014 ; Wang et al, 2019 ; Mao et al, 2021 ). This highlights the joint function of the rhizosphere, the pathogens and the plants all play important roles in the plant’s resistance to pathogen infection.…”

Endophytic Fungi: An Effective Alternative Source of Plant-Derived Bioactive Compounds for Pharmacological Studies

“…This discovery aroused the attention of mycologists and pharmaceutical chemists on endophytic fungi as a new source of bioactive substances and stimulated the interest in endophytic fungi as a sustainable source of plant metabolites. As shown in Table 1, many compounds that were isolated from endophytic fungi were also identified in some plant species as well as exhibited similar biological activity even though there were isolated from different sources, confirming endophytic fungi as an alternative source of bioactive compounds [19][20][21][22][23][24][25][26][27][28][29][30][31][32]. An overview of the recent literature surveys revealed that 51% of the bioactive substances isolated from endophytic fungi were previously unknown, with about 38% being isolated from soil microbiota [19].…”