“The root microbiome of medical cannabis plants has been largely unexplored due to past legal restrictions in many countries. Microbes that live on and within the tissue of cannabis provide advantages such as stimulating plant growth, helping it absorb minerals, providing protection against pathogen attacks, and influencing the production of secondary metabolites.” To gain more insight, a greenhouse trial was carried out with and without inoculants added to the growth substrate. “The results show that the use of microbial inoculants had an impact on the production of phytocannabinoids. This could have useful applications for optimizing cannabis cultivation practices and increasing the production of phytocannabinoids,” the researchers say.
The experiment was a randomized design with four inoculant treatments and five cultivars: CBD Therapy (THE), Euforia (EEA), Critical (CCL), CBD Sweet and Sour Widow (ECC), and CBD US (EUS) in a greenhouse trial of 3 months. The four inoculant treatments in this study were as follows: Ferticann (F, mixture of beneficial microbes containing 5,000 spores/g (0–120 µm, carrier silicate) of Rhizophagus irregularis, 109 CFU/g (0–120 µm and carrier dextrose) of Trichoderma harzianum and Bacillus subtilis, and microalga Dictyosphaerium chlorelloides); microbial suspension from forest soil (K1) dominated by planctobacteria; forest microbial suspension plus R. irregularis isolate DAOM 197198 (K2); and control (K0) without any inoculants.
“Plant biomass production showed higher levels in three of five cultivars inoculated with the arbuscular mycorrhizal fungus Rhizophagus irregularis and microbial suspension. The blossom dry weight of the cultivar THE was greater when inoculated with R. irregularis and microbial suspension than with no inoculation. Of course, increasing plant biomass and blossom dry weight are two important parameters for producing cannabis for medical applications,” the researchers add.
According to the researchers, all treatments significantly influenced the phytocannabinoid production as well, yet there were differences between treatments and cultivars. “The cultivar THE produced higher CBDV concentration, followed by the cultivars ECC and EUS, compared to the uninoculated control. The inoculation with Ferticann showed the highest increase in CBG concentrations in the CCL cultivar, while CBD was not detected with any of the treatments for the cultivar CCL. The highest concentration of CBGA was produced in ECC when inoculated with forest microbial suspension. However, the CCL cultivar showed a significant increase in the production of CBN, CBNA, and △9-THCA-A when inoculated with Ferticann, whereas CBC was not detectable for all treatments in CCL.”
The researchers also found that there is a core microbiome of shared bacterial and fungal taxa, with Streptomyces sp. always present in the roots of Cannabis cultivars. “It appears that cannabis roots are a favorable habitat for these microorganisms, and they may be deliberately recruiting these microbiomes to support their growth, nutrition, and other biological functions. An in-depth investigation of the microbiome and transcriptomics data should enhance our understanding of the role of the cannabis-associated microbiome during plant production.”
To read the complete research, go to www.frontiersin.org