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.
Highlights
The genus Abies comprises about 40 species that predominantly occur in boreal and subalpine forest zones (Liu, 1971)
Five hundred fifty-one bacterial isolates, obtained from the rhizosphere soil plus root tissue of A. nordmanniana plants grown in the field or in the greenhouse nurseries, were assigned to 126 strains based on morphological characterization and Universally Primed PCR (UP-PCR) fingerprinting (Supplementary Table 1)
Sixty bacterial strains representing the diversity of the strain collection were tested for their effect on A. nordmanniana seed germination in growth pouches
Summary
The genus Abies comprises about 40 species that predominantly occur in boreal and subalpine forest zones (Liu, 1971). The natural slow growth of A. nordmanniana represents a challenge to the growers as the trees only reach their harvesting stage after 10–13 years (Nielsen et al, 2011). It has been shown that seeds of many Abies species require a long period of cold stratification to break dormancy and enable germination (Zulueta-Rodríguez et al, 2015), and that a correct root and seedling development is essential for survival and establishment of Christmas trees after the nursery stage (Seifert, 2015). To lower the production time of A. nordmanniana, new approaches for promotion of growth and seed germination are of utmost importance for the Christmas tree industry
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
