ABSTRACT

Plant interactions with endophytic bacteria produce mutual benefits and contribute to environmental sustainability. Handroanthus impetiginosus (Mart. ex DC.) Mattos ‘pink lapacho’ (syn. Tabebuia impetiginosa, Bignoniaceae) is a medicinal, ornamental and forestal native tree from South and Mesoamerica. Plant growth promoting bacteria (PGPB) isolated from pink lapacho are scarcely described. The aim of this work was to isolate and characterize native endophytic bacteria from pink lapacho. Ten bacterial strains were isolated from leaves and six from roots of naturally growing trees in Luján (Central-Eastern region of Argentina). Endophytes were identified as Bacillus, Paenibacillus, Pseudomonas, Rhizobium, Rummeliibacillus and Methylobacterium genera, according to 16S rRNA gene sequencing and phylogenetic analysis. In the present study, a strain of the Rummelibacillus genus (L14) has been first ever reported as endophyte. This strain was capable of growing in Nfb medium and exhibited zinc solubilization ability. A high percentage of strains showed PGPB traits; namely 88% fixed nitrogen, 63% solubilized zinc, 69% solubilized phosphate and 63% produced indole compounds such as IAA. Most strains were salt tolerant that confer them a potential competitive advantage to survive in saline conditions. To the best of our knowledge, this is the first study reporting an approach to assess the diversity of cultivable endophytic bacteria of H. impetiginosus tree and its plant growth promoting capacity. The knowledge about this kind of associations could contribute to environmental sustainability by developing effective biofertilizers that minimize the use of chemical fertilizers and pesticides.

摘要

植物与内生细菌的相互作用产生互惠互利，并有助于环境的可持续性。Handroanthus impetiginosus (Mart. ex DC.) Mattos 'pink lapacho' (syn. Tabebuia impetiginosa , Bignoniaceae) 是一种来自南美洲和中美洲的药用、观赏和森林原生树。很少描述从粉红色拉帕乔中分离出的植物生长促进细菌 (PGPB)。这项工作的目的是从粉红色的 lapacho 中分离和表征天然内生细菌。从 Luján（阿根廷中东部地区）自然生长的树木的叶子和根中分离出 10 株细菌菌株。内生菌被鉴定为芽孢杆菌属、类芽孢杆菌属、假单胞菌属、根据 16S rRNA 基因测序和系统发育分析，发现了根瘤菌、Rummeliibacillus和Methylobacterium属。在本研究中，Rummelibacillus属 (L14) 菌株首次被报道为内生菌。该菌株能够在Nfb培养基中生长并表现出锌溶解能力。高比例的菌株表现出 PGPB 性状；即 88% 的固定氮、63% 的增溶锌、69% 的增溶磷酸盐和 63% 的吲哚化合物如 IAA。大多数菌株具有耐盐性，这赋予它们在盐碱条件下生存的潜在竞争优势。据我们所知，这是第一项报告评估可培养内生细菌多样性的方法的研究。H. impetiginosus树及其植物促生能力。通过开发有效的生物肥料，最大限度地减少化学肥料和杀虫剂的使用，有关这种关联的知识可以促进环境的可持续性。