Roodi Davood, Millner James P, McGill Craig, Johnson Richard D, Jauregui Ruy, Card Stuart D
School of Agriculture & Environment, Massey University, Palmerston North, Manawatu, New Zealand.
Agricultural Research, Education and Extension Organization (AREEO), Seed and Plant Improvement Institute, Karaj, Alborz, Iran.
PeerJ. 2020 Jul 10;8:e9514. doi: 10.7717/peerj.9514. eCollection 2020.
Plants are commonly colonized by a wide diversity of microbial species and the relationships created can range from mutualistic through to parasitic. Microorganisms that typically form symptomless associations with internal plant tissues are termed endophytes. Endophytes associate with most plant species found in natural and managed ecosystems. They are extremely important plant partners that provide improved stress tolerance to the host compared with plants that lack this symbiosis. Plant domestication has reduced endophyte diversity and therefore the wild relatives of many crop species remain untapped reservoirs of beneficial microbes. species display immense diversity and consequently provide the greatest assortment of products used by humans from a single plant genus important for agriculture, horticulture, bioremediation, medicine, soil conditioners, composting crops, and in the production of edible and industrial oils. Many endophytes are horizontally transmitted, but some can colonize the plant's reproductive tissues, and this gives these symbionts an efficient mechanism of propagation plant seed (termed vertical transmission).
This study surveyed 83 wild and landrace accessions composed of 14 different species with a worldwide distribution for seed-originating bacterial endophytes. Seed was stringently disinfected, sown within sterile tissue culture pots within a sterile environment and incubated. After approximately 1-month, direct isolation techniques were used to recover bacterial endophytes from roots and shoots of symptomless plants. Bacteria were identified based on the PCR amplification of partial 16S rDNA gene sequences and annotated using the BLASTn program against the NCBI rRNA database. A diversity index was used as a quantitative measure to reflect how many different bacterial species there were in the seed-originating microbial community of the accessions sampled.
Bacterial endophytes were recovered from the majority of the accessions screened. 16S rDNA gene sequencing identified 19 different bacterial species belonging to three phyla, namely Actinobacteria, Firmicutes and Proteobacteria with the most frequently isolated species being , and . was the dominant genus composing 56% of the culturable isolated bacterial community and was common in 77% of accessions possessing culturable bacterial endophytes. Two selected isolates of significantly promoted plant growth when inoculated into a cultivar of oilseed rape and inhibited the growth of the pathogen in dual culture. This is the first report that investigates the seed-originating endophytic microorganisms of wild species and highlights the microbiome as a resource for plant growth promoting bacteria and biological control agents.
植物通常被各种各样的微生物物种所定殖，所形成的关系从互利共生到寄生不等。通常与植物内部组织形成无症状关联的微生物被称为内生菌。内生菌与天然和人工管理生态系统中发现的大多数植物物种相关联。它们是极其重要的植物伙伴，与缺乏这种共生关系的植物相比，能为宿主提供更强的胁迫耐受性。植物驯化降低了内生菌的多样性，因此许多作物物种的野生近缘种仍是尚未开发的有益微生物库。该物种表现出巨大的多样性，因此从一个对农业、园艺、生物修复、医学、土壤改良剂、堆肥作物以及食用和工业油生产都很重要的单一植物属中提供了人类使用的最丰富多样的产品。许多内生菌是水平传播的，但有些可以定殖在植物的生殖组织中，这为这些共生体提供了一种通过植物种子传播的有效机制（称为垂直传播）。
本研究调查了83份野生和地方品种材料，这些材料由14个不同物种组成，分布于全球，用于研究种子源细菌内生菌。种子经过严格消毒，在无菌环境下播种于无菌组织培养盆中并进行培养。大约1个月后，采用直接分离技术从无症状植物的根和芽中分离细菌内生菌。基于部分16S rDNA基因序列的PCR扩增对细菌进行鉴定，并使用BLASTn程序在NCBI rRNA数据库中进行注释。使用多样性指数作为定量指标，以反映所采样材料的种子源微生物群落中有多少不同的细菌物种。
从大多数筛选的材料中分离出了细菌内生菌。16S rDNA基因测序鉴定出19种不同的细菌物种，属于三个门，即放线菌门、厚壁菌门和变形菌门，最常分离到的物种是[具体物种1]、[具体物种2]和[具体物种3]。[优势属名称]是优势属，占可培养分离细菌群落的56%，在77%具有可培养细菌内生菌的材料中常见。将两种选定的[优势属名称]分离株接种到油菜品种中时，显著促进了植物生长，并在共培养中抑制了病原菌[病原菌名称]的生长。这是第一份研究野生[物种名称]种子源内生微生物的报告，并突出了[物种名称]微生物组作为植物生长促进细菌和生物防治剂资源的重要性。
