Abstract
Plant growth-promoting rhizobacteria (PGPR) deploy several mechanisms to improve plant health, growth and yield. The aim of this study was to evaluate the efficacy of two Pseudomonas spp. strains and three Bacillus spp. strains used as single treatments and in consortia to improve the yield of Cannabis sativa and characterize the impact of these treatments on the diversity, structure and functions of the rhizosphere microbiome. Herein, we demonstrate a significant C. sativa yield increase up to 70% when inoculated with three different Pseudomonas spp./Bacillus spp. consortia but not with single inoculation treatments. This growth-promoting effect was observed in two different commercial soil substrates commonly used to grow cannabis: Promix and Canna coco. Marker-based genomic analysis highlighted Bacillus spp. as the main modulator of the rhizosphere microbiome diversity and Pseudomonas spp. as being strongly associated with plant growth promotion. We describe an increase abundance of predicted PGPR metabolic pathways linked with growth-promoting interactions in C. sativa.
Highlights
Plant-growth-promoting rhizobacteria (PGPR) are rhizosphere inhabitants associated with the root system that enhance the uptake of nutrients, produce beneficial phytohormones and protect against biotic and abiotic stressors, on the whole, augmenting plant growth and fitness (Cordovez et al, 2019)
We have identified C. sativa-growth-promoting consortia consisting of specific Pseudomonas spp. isolates and specific Bacillus spp. isolates
The analysis of marker-based Illumina sequencing from extracted rhizosphere DNA suggested that Bacillus spp. caused the greatest measurable shift in beta-diversity and that Pseudomonas spp., but not Bacillus spp., was associated to the plant-growth-promoting effect
Summary
Plant-growth-promoting rhizobacteria (PGPR) are rhizosphere inhabitants associated with the root system that enhance the uptake of nutrients, produce beneficial phytohormones and protect against biotic and abiotic stressors, on the whole, augmenting plant growth and fitness (Cordovez et al, 2019). Modulating the rhizosphere microbiome by inoculating with known PGPR has been practiced for nearly a century and is currently rooted in sustainable agriculture (Hartmann et al, 2008; Adesemoye et al, 2009; Bhattacharyya and Jha, 2012; Gupta et al, 2015). The use of PGPR which have the capacity to colonize the rhizosphere and promote plant growth and yield could greatly benefit and dynamize the nascent cannabis industry (Lyu et al, 2019). Initial studies have demonstrated the feasibility of this approach using a consortium of PGPR (Azospirillum brasilense, Gluconacetobacter diazotrophicus, Burkholderia ambifaria and Herbaspirillum seropedicae) or previously commercialized inoculants that potentiated the growth of C. sativa (Conant et al, 2017; Pagnani et al, 2018). The mechanism by which these inoculants benefited plant yield in consortia was not thoroughly explored
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