Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, 510642, No. 483, Wushan Road, Tianhe District, Guangdong, 510642, Guangzhou, China.
Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, 510642, Guangzhou, China.
BMC Microbiol. 2021 May 27;21(1):155. doi: 10.1186/s12866-021-02229-8.
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.
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.
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.
由青枯雷尔氏菌引起的桉树青枯病是桉树的重要病害。内生真菌是天然活性物质的重要来源，为植物病害的防治提供了新的突破。
本研究从健壮的蓝桉树枝和果实中分离得到 80 株内生真菌，通过形态特征评估和内部转录间隔区（ITS）区域 rRNA 基因序列分析，选择了 15 个具有代表性的内生真菌（MK120854-MK120868）进行分类学鉴定。基于形态特征，鉴定出了 13 个属，分别为叶点霉属、青霉属、胶孢炭疽菌属、拟青霉属、塔宾曲霉属、长喙壳属、枝孢属、拟盘多毛孢属、弯孢属、镰孢属、金孢子菌属、地丝霉属和拟珊瑚菌属。其中叶点霉属是主要的内生真菌，其定殖频率（CF）为 27.5%。大多数真菌分离物表现出抗菌活性。从长喙壳属 Eef-7、拟盘多毛孢属 Eef-9 和弯孢属 Eef-10 的粗提物中分离得到的化合物对测试细菌表现出较强的抑制作用，其中长喙壳属 Eef-7 被进一步大规模培养。从与蓝桉相关的内生真菌长喙壳属 Eef-7 中分离得到 3 个已知化合物，分别为 scorpinone（1）、5-deoxybostrycoidin（2）和 4-methyl-5,6-dihydro-2 H-pyran-2-one（3）。通过 1D 和 2D NMR 以及高分辨电喷雾质谱（HR-ESI-MS）分析和与文献值的光谱数据比较，确定了这些化合物的结构。化合物 1 和 2 对青枯雷尔氏菌表现出较弱的抗菌活性。
蓝桉内生真菌可能是抗菌剂的替代来源。长喙壳属 Eef-7 可以产生 2-氮杂蒽醌衍生物，对青枯雷尔氏菌表现出较弱的抑菌活性。
