Abstract

Eucalyptus is the main species for the forestry industry in Brazil. Biotechnology and, more recently, gene editing offer significant opportunities for rapid improvements in Eucalyptus breeding programs. However, the recalcitrance of Eucalyptus species to in vitro culture is also a major limitation for commercial deployment of biotechnology techniques in Eucalyptus improvement. We evaluated various clones of Eucalyptus urophylla for their in vitro regeneration potential identified a clone, BRS07-01, with considerably higher regeneration rate (85%) in organogenesis, and significantly higher than most works described in literature. Endophytic bacteria are widely reported to improve in vitro plant growth and development. Hence, we believe that inclusion of endophytic plant growth promoting bacteria enhanced was responsible for the improved plantlets growth and development of this clone under in vitro culture. Metagenomic analysis was performed to isolate and characterize the prominent endophytic bacteria on BRS07-01 leaf tissue in vitro micro-cultures, and evaluate their impact on plant growth promotion. The analysis revealed the presence of the phyla Firmicutes (35%), Proteobacteria (30%) and much smaller quantities of Actinobacteria, Bacteroidetes, Gemmatimonadetes, Crenarchaeota, Euryarchaeota and Acidobacteria. Of the thirty endophytic bacterial strains isolated, eleven produced indole-3-acetic acid. Two of the isolates were identified as Enterobacter sp. and Paenibacillus polymyxa, which are nitrogen-fixing and capable of phosphate and produce ammonium. These isolates also showed similar positive effects on the germination of common beans (Phaseolus spp.). The isolates will now be tested as a growth promoter in Eucalyptus in vitro cultures.

Graphic abstract

Graphical abstract for the methodology using cultivation independent and dependent methodologies to investigate the endophytic bacteria community from in vitro Eucalyptus urophylla BRS07-01.

中文翻译：

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尾叶桉 BRS07-01 体外植物相关内生细菌的宏基因组分析、分离和表征

摘要

桉树是巴西林业的主要树种。生物技术和最近的基因编辑为桉树育种计划的快速改进提供了重要的机会。然而，桉树物种对体外培养的顽固性也是桉树改良中生物技术技术商业部署的主要限制。我们评估了尾叶桉的各种克隆由于其体外再生潜力，鉴定了一个克隆 BRS07-01，在器官发生中具有相当高的再生率 (85%)，并且明显高于文献中描述的大多数作品。内生细菌被广泛报道可改善体外植物的生长和发育。因此，我们相信内生植物生长促进细菌的包含增强是在体外培养下该克隆的植物生长和发育改善的原因。进行宏基因组分析以在体外微量培养中分离和表征 BRS07-01 叶组织上的显着内生细菌，并评估它们对植物生长促进的影响。分析显示存在厚壁菌门 (35%)、变形菌门(30%) 和更少量的放线菌、拟杆菌、Gemmatimonadetes、Crenarchaeota、Euryarchaeota和酸杆菌。在分离的 30 种内生细菌菌株中，11 种产生吲哚-3-乙酸。其中两个分离株被鉴定为肠杆菌属。和多粘芽孢杆菌，其是固氮并且能够磷酸盐和农产品铵。这些分离株也对普通豆类 ( Phaseolus spp.)的发芽表现出类似的积极影响。这些分离物现在将作为桉树体外培养物中的生长促进剂进行测试。

图形摘要

使用独立和依赖培养方法研究体外桉树BRS07-01的内生细菌群落的方法学图形摘要。