Identification of Root-Associated Bacteria That Influence Plant Physiology, Increase Seed Germination, or Promote Growth of the Christmas Tree Species Abies nordmanniana

Abstract

Abies nordmanniana is used for Christmas tree production but poor seed germination and slow growth represent challenges for the growers. We addressed the plant growth promoting potential of root-associated bacteria isolated from A. nordmanniana . Laboratory screenings of a bacterial strain collection yielded several Bacillus and Paenibacillus strains that improved seed germination and produced indole-3-acetic acid. The impact of three of these strains on seed germination, plant growth and growth-related physiological parameters was then determined in greenhouse and field trials after seed inoculation, and their persistence was assessed by 16S rRNA gene-targeted bacterial community analysis. Two strains showed distinct and significant effects. Bacillus sp. s50 enhanced seed germination in the greenhouse but did not promote shoot or root growth. In accordance, this strain did not increase the level of soluble hexoses needed for plant growth but increased the level of storage carbohydrates. Moreover, strain s50 increased glutathione reductase and glutathione-S-transferase activities in the plant, which may indicate induction of systemic resistance during the early phase of plant development, as the strain showed poor persistence in the root samples (rhizosphere soil plus root tissue). Paenibacillus sp. s37 increased plant root growth, especially by inducing secondary root formation, under in greenhouse conditions, where it showed high persistence in the root samples. Under these conditions, it further it increased the level of soluble carbohydrates in shoots, and the levels of starch and non-structural carbohydrates in roots, stem and shoots. Moreover, it increased the chlorophyll level in the field trial. These findings indicate that this strain improves plant growth and vigor through effects on photosynthesis and plant carbohydrate reservoirs. The current results show that the two strains s37 and s50 could be considered for growth promotion programs of A. nordmanniana in greenhouse nurseries, and even under field conditions.

Linking Plant Secondary Metabolites and Plant Microbiomes: A Review

“…s50 increased the seed germination rate and systemic resistance to pathogens while Paenibacillus sp. s37 increased plant root growth in both greenhouse and field conditions ( Garcia-Lemos et al, 2020 ). Similar to those found in PGP rhizobacteria, several fungal species such as Trichoderma virens are also known to produce indole-3-acetic acid and other auxin-related compounds to positively impact the growth and development of plants, including rice, cotton, and Arabidopsis ( Contreras-Cornejo et al, 2009 ).…”

Synthetic community improves crop performance and alters rhizosphere microbial communities

“…Effect of SynCom application on plant growthThis study showed that the seed application of SynComs improved germination and early plant growth parameters. Enhanced germination percentage and rate in T1 treatments (SynCom-seed dressing) suggests that SynCom application helped to break seed dormancy, possibly by quickening metabolic processes(Garcia-Lemos et al, 2020;Rostamikia et al, 2016). Likewise, higher shoot growth parameters (7.4% higher shoot height and 5.1% higher shoot biomass) indicated that SynCom application at seedling stage can confer improved plant fitness at the early growth stage.…”

Complete Genome Sequence of Paenibacillus sp. Strain 37, a Plant Growth-Promoting Bacterium Isolated from the Rhizosphere of Abies nordmanniana (Nordmann Fir)

“…We report the complete genome sequence of Paenibacillus sp. strain 37, previously isolated from the rhizosphere of Abies nordmanniana (Nordmann fir) seedlings sampled at Baumschule Engler, Hohenlockstedt, Germany (53°58′30.5″N, 9°37′51.9″E) ( 2 ). A single colony of strain 37 was inoculated in lysogeny broth (LB) overnight at 28°C, and genomic DNA (gDNA) was purified using the NucleoSpin kit (Macherey-Nagel, DE) according to the manufacturer’s instructions.…”