Cannabis Microbiome and the Role of Endophytes in Modulating the Production of Secondary Metabolites: An Overview

Importance of Media Composition and Explant Type in Cannabis sativa Tissue Culture

Producing uniform Cannabis sativa (Cannabis) for medicinal/recreational flower production through sexual propagation has been problematic, leading to dominance of clonal propagation from "mother plants" in the cannabinoid industry, which also faces significant limitations. Cannabis tissue culture (TC) methods have been developed to overcome these challenges, but the long-term health and maintenance of Cannabis explants in TC have been largely overlooked in previous studies. The current study focused on the development of an efficient and optimized micropropagation protocol covering the entire process, with a specific focus on the health and performance in the multiplication stage. Multiplication media were formulated hormone-free to avoid longer-term vitrification issues, resulting in single-main-shoot cultures rather than multiple-shoot cultures. This instigated the use of stage II explant types different from the standard shoot tips previously used for multiple shoot cultures. Multiplication media were further improved from the basal salt composition via nitrogen and calcium additives. The optimized protocol was used on eight diverse Cannabis cultivars to test its applicability across various genetic backgrounds. Results indicated that the protocol was effective for conservation purposes across all cultivars and achieved good long-term multiplication rates for some but not all. The outcomes of this study mark a significant stride towards an efficient Cannabis TC methodology ready for more comprehensive industrial applications.

A three-years survey of microbial contaminants in industrial hemp inflorescences from two Italian cultivation sites

BACKGROUND

The use of industrial Cannabis sativa L. for recreational, cosmeceutical, nutraceutical, and medicinal purposes has gained momentum due to its rich content of valuable phytochemicals, such as cannabidiol (CBD) and cannabigerol (CBG). However, there are concerns regarding the risk of microbial contamination in plants grown outside controlled environments. Microbes associated with hemp can be either epiphytes or endophytes and may pose a risk of infectious illness for humans.

METHODS

Seven Italian hemp genotypes, including Bernabeo, Carmagnola, Carmaleonte, Codimono, CS, Eletta Campana, and Fibranova, were cultivated in two distinct geographic locations, Catania and Rovigo, for three consecutive years from 2019 to 2021. Total aerobic microbes (TAMC), total combined yeasts/moulds (TYMC), the presence of bile-tolerant Gram-negative bacteria, and the absence of Escherichia coli and Salmonella spp. were evaluated and compared. The main phytocannabinoid content was measured and correlated with microbial contamination.

RESULTS

Most samples analyzed in this study did not meet the European Pharmacopoeia microbiological limits. The detection of potential pathogens, such as E. coli and Salmonella spp., in the samples indicates that the use of inflorescences may represent a possible source of infection. Microbial contamination varied among harvesting seasons and production sites, with agroclimatic conditions influencing microbial load and composition. The presence of potentially pathogenic bacteria was less associated with seasonal climate variability and more likely affected by sporadic contamination from external sources. CBD concentration exhibited a negative correlation with bile-tolerant Gram-negative bacteria and total yeasts/moulds levels. Samples with lower CBD content were more contaminated than those with higher CBD levels, suggesting a potential protective effect of this phytochemical on the plant.

CONCLUSIONS

The threshing residues (inflorescences, floral bracts, and leaves) of industrial hemp varieties represent a valuable product and a source of beneficial phytochemicals that warrants further exploration. While post-harvest sterilization methods may reduce microbiological risks, they may also degrade heat- and light-sensitive bioactive phytochemicals. The most promising strategy involves implementing best agronomic practices to maintain healthy and uncontaminated cultures. Rigorous monitoring and quality certification protocols are essential to mitigate the microbiological risk associated with the consumption of hemp-derived products.

Bioaerosol Exposures and Respiratory Diseases in Cannabis Workers

PURPOSE OF REVIEW

This review investigates occupational inhalation hazards associated with biologically derived airborne particles (bioaerosols) generated in indoor cannabis cultivation and manufacturing facilities.

RECENT FINDINGS

Indoor cannabis production is growing across the US as are recent reports of respiratory diseases among cannabis workers, including occupational asthma morbidity and mortality. More information is needed to understand how bioaerosol exposure in cannabis facilities impacts worker health and occupational disease risk. Preliminary studies demonstrate a significant fraction of airborne particles in cannabis facilities are comprised of fungal spores, bacteria, and plant material, which may also contain hazardous microbial metabolites and allergens. These bioaerosols may pose pathogenic, allergenic, toxigenic, and pro-inflammatory risks to workers. The absence of multi-level, holistic bioaerosol research in cannabis work environments necessitates further characterization of the potential respiratory hazards and effective risk prevention methods to safeguard occupational health as the cannabis industry continues to expand across the US and beyond.

Microbial regulation of plant secondary metabolites: Impact, mechanisms and prospects

Plant secondary metabolites possess a wide range of pharmacological activities and play crucial biological roles. They serve as both a defense response during pathogen attack and a valuable drug resource. The role of microorganisms in the regulation of plant secondary metabolism has been widely recognized. The addition of specific microorganisms can increase the synthesis of secondary metabolites, and their beneficial effects depend on environmental factors and plant-related microorganisms. This article summarizes the impact and regulatory mechanisms of different microorganisms on the main secondary metabolic products of plants. We emphasize the mechanisms by which microorganisms regulate hormone levels, nutrient absorption, the supply of precursor substances, and enzyme and gene expression to promote the accumulation of plant secondary metabolites. In addition, the possible negative feedback regulation of microorganisms is discussed. The identification of additional unknown microbes and other driving factors affecting plant secondary metabolism is essential. The prospects for further analysis of medicinal plant genomes and the establishment of a genetic operation system for plant secondary metabolism research are proposed. This study provides new ideas for the use of microbial resources for biological synthesis research and the improvement of crop anti-inverse traits for the use of microbial resources.

Bacterial endophytic community composition varies by hemp cultivar in commercially sourced seed

The seed-endophytic bacterial community is a potentially beneficial and heritable fraction of the plant microbiome. Its utilization as a sustainable crop improvement strategy could be especially valuable for species such as hemp, where production is being scaled up and new challenges will be faced in managing crop productivity and health. However, little is known about the makeup and variation of the hemp seed microbiome. This study profiled the endophytic bacterial communities harboured by 16 hemp cultivars sourced from commercial suppliers in Europe. A 16S rDNA amplicon sequencing approach identified 917 amplicon sequence variants across samples. Taxonomic classification of sequences revealed 4 phyla and 87 genera to be represented in the dataset. Several genera were widespread while some were specific to one or a few cultivars. Flavobacterium, Pseudomonas, and Pantoea were notable in their high overall abundance and prevalence, but community composition was variable and no one taxon was universally abundant, suggesting a high degree of flexibility in community assembly. Taxonomic composition and alpha diversity differed among cultivars, though further work is required to understand the relative influence of hemp genetic factors on community structure. The taxonomic profiles presented here can be used to inform further work investigating the functional characteristics and potential plant-growth-promoting traits of seed-borne bacteria in hemp.

Integrated Management of Pathogens and Microbes in Cannabis sativa L. (Cannabis) under Greenhouse Conditions

The increased cultivation of high THC-containing Cannabis sativa L. (cannabis), particularly in greenhouses, has resulted in a greater incidence of diseases and molds that can negatively affect the growth and quality of the crop. Among them, the most important diseases are root rots (Fusarium and Pythium spp.), bud rot (Botrytis cinerea), powdery mildew (Golovinomyces ambrosiae), cannabis stunt disease (caused by hop latent viroid), and a range of microbes that reduce post-harvest quality. An integrated management approach to reduce the impact of these diseases/microbes requires combining different approaches that target the reproduction, spread, and survival of the associated pathogens, many of which can occur on the same plant simultaneously. These approaches will be discussed in the context of developing an integrated plan to manage the important pathogens of greenhouse-grown cannabis at different stages of plant development. These stages include the maintenance of stock plants, propagation through cuttings, vegetative growth of plants, and flowering. The cultivation of cannabis genotypes with tolerance or resistance to various pathogens is a very important approach, as well as the maintenance of pathogen-free stock plants. When combined with cultural approaches (sanitation, management of irrigation, and monitoring for diseases) and environmental approaches (greenhouse climate modification), a significant reduction in pathogen development and spread can be achieved. The use of preventive applications of microbial biological control agents and reduced-risk biorational products can also reduce disease development at all stages of production in jurisdictions where they are registered for use. The combined use of promising strategies for integrated disease management in cannabis plants during greenhouse production will be reviewed. Future areas for research are identified.

Cannabis Roots: Therapeutic, Biotechnological and Environmental Aspects

Since the legalization of recreational cannabis in Canada in 2018, the number of licenses for this crop has increased significantly, resulting in an increase in waste generated. Nevertheless, cannabis roots were once used for their therapeutic properties, indicating that they could be valued today rather than dismissed. This review will focus on both traditional therapeutic aspects and potential use of roots in modern medicine while detailing the main studies on active phytomolecules found in cannabis roots. The environmental impact of cannabis cultivation and current knowledge of the root-associated microbiome are also presented as well as their potential applications in biotechnology and phytoremediation. Thus, several high added-value applications of cannabis roots resulting from scientific advances in recent years can be considered to remove them from discarded residues.

Unlocking the potential of bacterial endophytes from medicinal plants for drug discovery

Among the plant-associated microorganisms, the so-called endophytes continue to attract much attention because of their ability not only to protect host plants from biotic and abiotic stress factors, but also the potential to produce bioactive secondary metabolites. The latter property can elicit growth-promoting effects on plants, as well as boost the production of plant-specific secondary metabolites with valuable pharmacological properties. In addition, endophyte-derived secondary metabolites may be a rich source for the discovery of drugs to treat various diseases, including infections and cancer. However, the full potential of endophytes to produce bioactive secondary metabolites is often not revealed upon conventional cultivation in the laboratory. New advances in genomics and metabolic engineering offer exciting opportunities for the exploration and exploitation of endophytes' biosynthetic potential. This review focuses on bacterial endophytes of medicinal plants, some of their secondary metabolites and recent advances in deciphering their biosynthesis. The latter may assist in genetic engineering efforts aimed at the discovery of novel bioactive compounds with the potential to be developed into drugs.

Changes in the Bacterial Communities of Biocomposites with Different Flame Retardants

In today's world, the use of environmentally friendly materials is strongly encouraged. These materials derive from primary raw materials of plant origin, like fibrous hemp, flax, and bamboo, or recycled materials, such as textiles or residual paper, making them suitable for the growth of microorganisms. Here, we investigate changes in bacterial communities in biocomposites made of hemp shives, corn starch, and either expandable graphite or a Flovan compound as flame retardants. Using Next Generation Sequencing (NGS), we found that after 12 months of incubation at 22 °C with a relative humidity of 65%, Proteobacteria accounted for >99.7% of the microbiome in composites with either flame retardant. By contrast, in the absence of flame retardants, the abundance of Proteobacteria decreased to 32.1%, while Bacteroidetes (36.6%), Actinobacteria (8.4%), and Saccharobacteria (TM7, 14.51%) appeared. Using the increasing concentrations of either expandable graphite or a Flovan compound in an LB medium, we were able to achieve up to a 5-log reduction in the viability of Bacillus subtilis, Pseudomonas aeruginosa, representatives of the Bacillus and Pseudomonas genera, the abundance of which varied in the biocomposites tested. Our results demonstrate that flame retardants act on both Gram-positive and Gram-negative bacteria and suggest that their antimicrobial activities also have to be tested when producing new compounds.

Fungal and mycotoxin contaminants in cannabis and hemp flowers: implications for consumer health and directions for further research

Medicinal and recreational uses of Cannabis sativa, commonly known as cannabis or hemp, has increased following its legalization in certain regions of the world. Cannabis and hemp plants interact with a community of microbes (i.e., the phytobiome), which can influence various aspects of the host plant. The fungal composition of the C. sativa phytobiome (i.e., mycobiome) currently consists of over 100 species of fungi, which includes phytopathogens, epiphytes, and endophytes, This mycobiome has often been understudied in research aimed at evaluating the safety of cannabis products for humans. Medical research has historically focused instead on substance use and medicinal uses of the plant. Because several components of the mycobiome are reported to produce toxic secondary metabolites (i.e., mycotoxins) that can potentially affect the health of humans and animals and initiate opportunistic infections in immunocompromised patients, there is a need to determine the potential health risks that these contaminants could pose for consumers. This review discusses the mycobiome of cannabis and hemp flowers with a focus on plant-infecting and toxigenic fungi that are most commonly found and are of potential concern (e.g., Aspergillus, Penicillium, Fusarium, and Mucor spp.). We review current regulations for molds and mycotoxins worldwide and review assessment methods including culture-based assays, liquid chromatography, immuno-based technologies, and emerging technologies for these contaminants. We also discuss approaches to reduce fungal contaminants on cannabis and hemp and identify future research needs for contaminant detection, data dissemination, and management approaches. These approaches are designed to yield safer products for all consumers.

Stigmas of holoparasitic Phelipanche arenaria (Orobanchaceae) - a suitable ephemeric flower habitat for development unique microbiome

BACKGROUND

Microbial communities have occasionally been observed in part of the ephemeric reproductive structure of floral stigmas, but their prevalence, phylogenetic diversity and ecological roles are understudied. This report describes the first study of bacterial and fungal communities in immature and mature stigma tissue of the endangered holoparasitic plant Phelipanche arenaria. Culture-dependent methods coupled with next-generation sequencing indicated that a small surface of the flower stigma was an unexpectedly rich and diverse microhabitat for colonization of microbial. We also compared the enzymatic activity of the bacterial communities between immature and mature stigmas samples.

RESULTS

Using high-throughput sequencing methods, we identified and classified 39 to over 51 OTUs per sample for bacterial OTUs represented by Pantoea agglomerans and P. ananatis, comprising 50.6%, followed by Pseudomonas, Luteibacter spp., Sphingomonas spp. with 17% of total frequency. The bacterial profile of immature stigmas of P. arenaria contained unique microorganisms (21 of the most numerous OTUs) that were not confirmed in mature stigmas. However, the enzymatic activity of bacteria in mature stigmas of P. arenaria showed more activity than observed in immature stigmas. In the fungal profile, we recorded even 80 OTUs in mature stigmas, consisting of Capnodiales 45.03% of the total abundance with 28.27% of frequency was created by Alternaria eichhorniae (10.55%), Mycosphaerella tassiana (9.69%), and Aureobasidium pullulans (8.03%). Additionally, numerous putative plant growth-promoting bacteria, fungal pathogens and pathogen-antagonistic yeasts were also detected.

CONCLUSIONS

Our study uncovered that P. arenaria stigmas host diverse bacterial and fungal communities. These microorganisms are well known and have been described as beneficial for biotechnological and environmental applications (e.g., production of different enzymes and antimicrobial compounds). This research provided valuable insight into the parasitic plant-microbe interactions.

Enhanced production of select phytocannabinoids in medical Cannabis cultivars using microbial consortia

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 sativa L. similar to other plants, 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 insight into the microbial communities of C. sativa cultivars with different tetrahydrocannabinol (THC) and cannabidiol (CBD) profiles, a greenhouse trial was carried out with and without inoculants added to the growth substrate. Illumina MiSeq metabarcoding was used to analyze the root and rhizosphere microbiomes of the five cultivars. 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. Increasing plant biomass and blossom dry weight are two important parameters for producing cannabis for medical applications. In mature Cannabis, 12 phytocannabinoid compounds varied among cultivars and were affected by inoculants. Significant differences (p ≤ 0.01) in concentrations of cannabidivarinic acid (CBDVA), cannabidivarin (CBDV), cannabigerol (CBG), cannabidiol (CBD), and cannabigerolic acid (CBGA) were observed in all Cannabis cultivars when amended with F, K1, and K2 inoculants. We found microbes that were shared among cultivars. For example, Terrimicrobium sp., Actinoplanes sp., and Trichoderma reesei were shared by the cultivars ECC-EUS-THE, CCL-ECC, and EUS-THE, respectively. Actinoplanes sp. is a known species that produces phosphatase enzymes, while Trichoderma reesei is a fungal train that produces cellulase and contributes to organic matter mineralization. However, the role of Terrimicrobium sp. as an anaerobic bacterium remains unknown. This study demonstrated that the use of inoculants had an impact on the production of phytocannabinoids in five Cannabis cultivars. These inoculants could have useful applications for optimizing cannabis cultivation practices and increasing the production of phytocannabinoids.

Cannabis: a multifaceted plant with endless potentials

Cannabis sativa, also known as "hemp" or "weed," is a versatile plant with various uses in medicine, agriculture, food, and cosmetics. This review attempts to evaluate the available literature on the ecology, chemical composition, phytochemistry, pharmacology, traditional uses, industrial uses, and toxicology of Cannabis sativa. So far, 566 chemical compounds have been isolated from Cannabis, including 125 cannabinoids and 198 non-cannabinoids. The psychoactive and physiologically active part of the plant is a cannabinoid, mostly found in the flowers, but also present in smaller amounts in the leaves, stems, and seeds. Of all phytochemicals, terpenes form the largest composition in the plant. Pharmacological evidence reveals that the plants contain cannabinoids which exhibit potential as antioxidants, antibacterial agents, anticancer agents, and anti-inflammatory agents. Furthermore, the compounds in the plants have reported applications in the food and cosmetic industries. Significantly, Cannabis cultivation has a minimal negative impact on the environment in terms of cultivation. Most of the studies focused on the chemical make-up, phytochemistry, and pharmacological effects, but not much is known about the toxic effects. Overall, the Cannabis plant has enormous potential for biological and industrial uses, as well as traditional and other medicinal uses. However, further research is necessary to fully understand and explore the uses and beneficial properties of Cannabis sativa.

Recent Research on Cannabis sativa L.: Phytochemistry, New Matrices, Cultivation Techniques, and Recent Updates on Its Brain-Related Effects (2018-2023)

Cannabis sativa L. is a plant that humankind has been using for millennia. The basis of its widespread utilization is its adaptability to so many different climatic conditions, with easy cultivability in numerous diverse environments. Because of its variegate phytochemistry, C. sativa has been used in many sectors, although the discovery of the presence in the plant of several psychotropic substances (e.g., Δ⁹-tetrahydrocannabinol, THC) caused a drastic reduction of its cultivation and use together with its official ban from pharmacopeias. Fortunately, the discovery of Cannabis varieties with low content of THC as well as the biotechnological development of new clones rich in many phytochemical components endorsed with peculiar and many important bioactivities has demanded the reassessment of these species, the study and use of which are currently experiencing new and important developments. In this review we focus our attention on the phytochemistry, new matrices, suitable agronomic techniques, and new biological activities developed in the five last years.

Functional characterization and transcriptional activity analysis of Dryopteris fragrans farnesyl diphosphate synthase genes

Farnesyl diphosphate synthase (FPS), a key enzyme of the terpene metabolic pathway, catalyzes the precursor of sesquiterpene compounds farnesyl diphosphate (FPP) synthesis, and plays an important role in regulating plant growth and development. Dryopteris fragrans is a medicinal plant rich terpenoids. In this study, the function of the gene was verified in vitro and in vivo, the promoter of the gene was amplified and its transcriptional activity was analyzed. In the present study, we report the molecular cloning and functional characterization of DfFPS1 and DfFPS2, two FPS genes from D. fragrans. We found that the two genes were evolutionarily conserved. Both DfFPS genes were highly expressed in the gametophyte and mature sporophyte leaves, and their expression levels increased in response to methyl jasmonate (MeJA) and high temperature. Both DfFPS proteins were localized in the cytoplasm and could catalyze FPP synthesis in vitro. We also found that the overexpression of DfFPS genes in tobacco plants promoted secondary metabolite accumulation but exhibited negligible effect on plant growth and development. However, the transgenic plants exhibited tolerance to high temperature and drought. The promoters of the two genes were amplified using fusion primer and nested integrated polymerase chain reaction (FPNI-PCR). The promoter sequences were truncated and their activity was examined using the β-glucuronidase (GUS) gene reporter system in tobacco leaves, and we found that both genes were expressed in the stomata. The transcriptional activity of the promoters was found to be similar to the expression pattern of the genes, and the transcriptional core regions of the two genes were mainly between -943 bp and -740 bp of proDfFPS1. Therefore, we present a preliminary study on the function and transcriptional activity of the FPS genes of D. fragrans and provide a basis for the regulation of terpene metabolism in D. fragrans. The results also provide a novel basis for the elucidation of terpene metabolic pathways in ferns.

Co-Application of Silver Nanoparticles and Symbiotic Fungus Piriformospora indica Improves Secondary Metabolite Production in Black Rice

In the current research, unique Nano-Embedded Fungus (NEF), made by the synergic association of silver nanoparticles (AgNPs) and endophytic fungus (Piriformospora indica), is studied, and the impact of NEF on black rice secondary metabolites is reported. AgNPs were synthesized by chemical reduction process using the temperature-dependent method and characterized for morphological and structural features through UV visible absorption spectroscopy, zeta potential, XRD, SEM-EDX, and FTIR spectroscopy. The NEF, prepared by optimizing the AgNPs concentration (300 ppm) in agar and broth media, showed better fungal biomass, colony diameter, spore count, and spore size than the control P. indica. Treatment with AgNPs, P. indica, and NEF resulted in growth enhancement in black rice. NEF and AgNPs stimulated the production of secondary metabolites in its leaves. The concentrations of chlorophyll, carotenoids, flavonoids, and terpenoids were increased in plants inoculated with P. indica and AgNPs. The findings of the study highlight the synergistic effect of AgNPs and the fungal symbionts in augmenting the secondary metabolites in leaves of black rice.

Rhizobacterial compositions and their relationships with soil properties and medicinal bioactive ingredients in Cinnamomum migao

Introduction

Rhizobacterial communities and their metabolites can affect plant growth, development, and stress resistance, as well as the biosynthesis and accumulation of bioactive compounds in medicinal plants. This relationship has been well-characterized in many medicinal herbs, although much less commonly in medicinal trees.

Methods

Here, we analyzed the composition and structure of Cinnamomum migao rhizobacterial communities across nine growing regions in Yunnan, Guizhou and Guangxi, China, as well as differences in soil properties and fruit bioactive compounds.

Results

Results showed that the C. migao rhizobacterial communities exhibited high species richness, but location-specific differences in structure. Site-specific differences in soil properties and bioactive compounds were also observed. Furthermore, rhizobacterial community compositions were correlated with both soil properties and fruit bioactive compounds, metabolism-related functions were most common in C. migao rhizobacteria.

Discussion

Several bacterial genera, including Acidothermus, Acidibacter, Bryobacter, Candidatus_Solibacter, and Acidimicrobiales, potentially promote the biosynthesis and accumulation of 1,8-cineole, cypressene, limonene, and α-terpineol, Nitrospira and Alphaproteobacteria may play an inhibitory role. Finally, our results emphasized the critical role that soil pH and nitrogen levels play in driving rhizobacterial community structure, and specific functional bacteria can also counteract with soil properties, Acidibacter and Nitrospira can affect soil pH and nitrogen effectiveness. Overall, this study provides additional insight into the complex correlation of rhizosphere microorganisms with bioactive ingredients and soil properties of medicinal plants.

Characterization of the Cultivable Endophytic Bacterial Community of Seeds and Sprouts of Cannabis sativa L. and Perspectives for the Application as Biostimulants

Endophytes are beneficial microorganisms exerting growth-promoting activities in plants; they are most often located within the plant intercellular spaces and can be found in all plant tissues, including roots, leaves, stems, flowers, and seeds. In this work, we investigated the cultivable bacterial community of the seeds and the two-week sprouts of the Cannabis sativa L. cultivar “Futura 75”. Endophytes were genotypically and phenotypically characterized and were exposed to different concentrations of seed extracts to verify their susceptibility. A bacterial strain among all the isolates was selected for germination tests of C. sativa in different experimental conditions. The results revealed the dominance of Firmicutes (Staphylococcus sp.) among the isolated strains. Two strains were different from the others for indole-3-acetic acid (IAA) production and for their resistance patterns towards abiotic and biotic stresses. The Sphingomonas sp. strain Can_S11 (Alphaproteobacteria) showed a potential ability to increase the nutraceutical features of its sprouts, particularly an increase in the polyphenol content and antioxidant activity. None of the isolated strains were susceptible to the seed extracts, which were previously tested as antimicrobial and antibiofilm agents against human pathogenic bacteria. The results open new perspectives for the study of the endophytes of C. sativa as possible biostimulants.

Pyoluteorin and 2,4-diacetylphloroglucinol are major contributors to Pseudomonas protegens Pf-5 biocontrol against Botrytis cinerea in cannabis

Pseudomonas protegens Pf-5 is an effective biocontrol agent that protects many crops against pathogens, including the fungal pathogen Botrytis cinerea causing gray mold disease in Cannabis sativa crops. Previous studies have demonstrated the important role of antibiotics pyoluteorin (PLT) and 2,4-diacetylphloroglucinol (DAPG) in Pf-5-mediated biocontrol. To assess the potential involvement of PLT and DAPG in the biocontrol exerted by Pf-5 against B. cinerea in the phyllosphere of C. sativa, two knockout Pf-5 mutants were generated by in-frame deletion of genes pltD or phlA, required for the synthesis of PLT or DAPG respectively, using a two-step allelic exchange method. Additionally, two complemented mutants were constructed by introducing a multicopy plasmid carrying the deleted gene into each deletion mutant. In vitro confrontation assays revealed that deletion mutant ∆pltD inhibited B. cinerea growth significantly less than wild-type Pf-5, supporting antifungal activity of PLT. However, deletion mutant ∆phlA inhibited mycelial growth significantly more than the wild-type, hypothetically due to a co-regulation of PLT and DAPG biosynthesis pathways. Both complemented mutants recovered in vitro inhibition levels similar to that of the wild-type. In subsequent growth chamber inoculation trials, characterization of gray mold disease symptoms on infected cannabis plants revealed that both ∆pltD and ∆phlA significantly lost a part of their biocontrol capabilities, achieving only 10 and 19% disease reduction respectively, compared to 40% achieved by inoculation with the wild-type. Finally, both complemented mutants recovered biocontrol capabilities in planta similar to that of the wild-type. These results indicate that intact biosynthesis pathways for production of PLT and DAPG are required for the optimal antagonistic activity of P. protegens Pf-5 against B. cinerea in the cannabis phyllosphere.

Enhancement of growth and Cannabinoids content of hemp (Cannabis sativa) using arbuscular mycorrhizal fungi

This study aimed to investigate the efficiency of arbuscular mycorrhizal fungi (AMF) to promote growth and cannabinoid yield of Cannabis sativa KKU05. A completely randomized design (CRD) was conducted with six replications for 60 days. Two different species of AMF, Rhizophagus prolifer PC2-2 and R. aggregatus BM-3 g3 were selected as inocula and compared with two non-mycorrhizal controls, one without synthetic fertilizer and one with synthetic NPK fertilizer. The unfertilized non-mycorrhizal plants had the lowest performance, whereas plants inoculated with R. aggregatus BM-3 g3 performed best, both in terms of plant biomass and concentrations of CBD and THC. There were no significant differences in plant biomass and cannabinoid concentrations between non-mycorrhizal plants that received synthetic fertilizer and mycorrhizal plants with inoculum of R. prolifer PC2-2. Our data demonstrate the great potential for cannabis cultivation without risking deterioration of soil structure, such as soil hardening and increased acidity, which might be induced by long-term use of synthetic fertilizer.

Microbial Metabolites Beneficial to Plant Hosts Across Ecosystems

Plants are intimately connected with their associated microorganisms. Chemical interactions via natural products between plants and their microbial symbionts form an important aspect in host health and development, both in aquatic and terrestrial ecosystems. These interactions range from negative to beneficial for microbial symbionts as well as their hosts. Symbiotic microbes synchronize their metabolism with their hosts, thus suggesting a possible coevolution among them. Metabolites, synthesized from plants and microbes due to their association and coaction, supplement the already present metabolites, thus promoting plant growth, maintaining physiological status, and countering various biotic and abiotic stress factors. However, environmental changes, such as pollution and temperature variations, as well as anthropogenic-induced monoculture settings, have a significant influence on plant-associated microbial community and its interaction with the host. In this review, we put the prominent microbial metabolites participating in plant-microbe interactions in the natural terrestrial and aquatic ecosystems in a single perspective and have discussed commonalities and differences in these interactions for adaptation to surrounding environment and how environmental changes can alter the same. We also present the status and further possibilities of employing chemical interactions for environment remediation. Our review thus underlines the importance of ecosystem-driven functional adaptations of plant-microbe interactions in natural and anthropogenically influenced ecosystems and their possible applications.

Production and Functionalities of Specialized Metabolites from Different Organic Sources

Medicinal plants are rich sources of specialized metabolites that are of great importance to plants, animals, and humans. The usefulness of active biological compounds cuts across different fields, such as agriculture, forestry, food processing and packaging, biofuels, biocatalysts, and environmental remediation. In recent years, research has shifted toward the use of microbes, especially endophytes (bacteria, fungi, and viruses), and the combination of these organisms with other alternatives to optimize the production and regulation of these compounds. This review reinforces the production of specialized metabolites, especially by plants and microorganisms, and the effectiveness of microorganisms in increasing the production/concentration of these compounds in plants. The study also highlights the functions of these compounds in plants and their applications in various fields. New research areas that should be explored to produce and regulate these compounds, especially in plants and microbes, have been identified. Methods involving molecular studies are yet to be fully explored, and next-generation sequencing possesses an interesting and reliable approach.

Bacillus velezensis EEAM 10B Strengthens Nutrient Metabolic Process in Black Soldier Fly Larvae (Hermetia illucens) via Changing Gut Microbiome and Metabolic Pathways

Insects are a potential alternative protein source to solve the food shortage crisis. Previous studies have illustrated that probiotics can improve the substrate conversion efficiency of insects and increase insect protein content. However, the effects of probiotics on insect physiology and nutrient metabolism are still not well understood. Here, the black soldier fly larvae (BSFL), Hermetia illucens (Diptera: Stratiomyidae), was used as a study subject to deeply investigate the specific interaction among a novel probiotic, Bacillus velezensis EEAM 10B (10B), intestinal microbiota, and the host. In this study, the effects of 10B on the survival and physiology of BSFL were first analyzed. It shows that 10B significantly elevated the substrate conversion rate, average dry weight, and protein content of BSFL by 5%, 0.13 g/pc, and 8%, respectively. Then, we assessed the effect of 10B on the microbial community composition in the gut and frass of BSFL using Illumina Miseq sequencing. It shows that 10B significantly altered the microbial composition of the gut, but not that of the frass. Pearson’s correlation analysis further showed that the Bacillus, unclassified_of_Caloramatoraceae, and Gracilibacillus were positively correlated with the survival rate, crude protein content, and substrate conversion rate of BSFL. To further investigate the effect of 10B on host metabolism, metabolic analyses on germ-free BSFL, monobacterial intestinal BSFL, and natural BSFL were also performed. The results proved that 10B (i) played a vital role in the survival of BSFL; and (ii) regulated the amino acid synthetic and metabolic process of BSFL, thus leading to the rise of the protein content of BSFL. In addition, vitamin backfill assays verified that the BSFL survival rate was significantly improved by supplying the germ-free BSFL with riboflavin, which further suggests that 10B determines the survival of BSFL via delivering riboflavin. Overall, this study provides a reference for understanding the comprehensive contribution of a specific probiotic to its host.

Antinociceptive effects of minor cannabinoids, terpenes and flavonoids in Cannabis

Cannabis has been used for centuries for its medicinal properties. Given the dangerous and unpleasant side effects of existing analgesics, the chemical constituents of Cannabis have garnered significant interest for their antinociceptive, anti-inflammatory and neuroprotective effects. To date, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) remain the two most widely studied constituents of Cannabis in animals. These studies have led to formulations of THC and CBD for human use; however, chronic pain patients also use different strains of Cannabis (sativa, indica and ruderalis) to alleviate their pain. These strains contain major cannabinoids, such as THC and CBD, but they also contain a wide variety of cannabinoid and noncannabinoid constituents. Although the analgesic effects of Cannabis are attributed to major cannabinoids, evidence indicates other constituents such as minor cannabinoids, terpenes and flavonoids also produce antinociception against animal models of acute, inflammatory, neuropathic, muscle and orofacial pain. In some cases, these constituents produce antinociception that is equivalent or greater compared to that produced by traditional analgesics. Thus, a better understanding of the extent to which these constituents produce antinociception alone in animals is necessary. The purposes of this review are to (1) introduce the different minor cannabinoids, terpenes, and flavonoids found in Cannabis and (2) discuss evidence of their antinociceptive properties in animals.

Biocontrol Activity of Bacillus spp. and Pseudomonas spp. Against Botrytis cinerea and Other Cannabis Fungal Pathogens

Gray mold caused by Botrytis cinerea is one of the most widespread and damaging diseases in cannabis crops worldwide. With challenging restrictions on pesticide use and few effective control measures, biocontrol agents are needed to manage this disease. The aim of this study was to identify bacterial biocontrol agents with wide-spectrum activity against B. cinerea and other cannabis fungal pathogens. Twelve Bacillus and Pseudomonas strains were first screened with in vitro confrontational assays against 10 culturable cannabis pathogens, namely B. cinerea, Sclerotinia sclerotiorum, Fusarium culmorum, F. sporotrichoides, F. oxysporum, Nigrospora sphaerica, N. oryzae, Alternaria alternata, Phoma sp., and Cercospora sp. Six strains displaying the highest inhibitory activity, namely Bacillus velezensis LBUM279, FZB42, LBUM1082, Bacillus subtilis LBUM979, P. synxantha LBUM223, and P. protegens Pf-5, were further assessed in planta where all, except LBUM223, significantly controlled gray mold development on cannabis leaves. Notably, LBUM279 and FZB42 reduced disease severity by at least half compared with water-treated plants and prevented lesion development and/or sporulation up to 9 days after pathogen inoculation. Genomes of LBUM279, LBUM1082, and LBUM979 were sequenced de novo and taxonomic affiliations were determined to ensure nonrelatedness with pathogenic strains. Moreover, the genomes were exempt of detrimental genes encoding major toxins and virulence factors that could otherwise pose a biosafety risk when used on crops. Eighteen gene clusters of potential biocontrol interest were also identified. To our knowledge, this is the first reported attempt to control cannabis fungal diseases in planta by direct antagonism with beneficial bacteria.

Industry-Based Misconceptions Regarding Cross-Pollination of Cannabis spp

Cross-pollination of commercial crops has been an ongoing issue in many species. Cannabis spp. encompasses the classifications of marijuana [high in Δ9-tetrahydrocannabinol (THC)] and hemp (below 0.3% THC). As such, cannabis is the most recent crop facing the dilemma of cross-pollination and is leading to litigation. These litigations are driven by the large misunderstanding of the impacts of cross-pollination within the cannabis industry. The misconception is that if hemp is cross-pollinated by high THC cannabis, the hemp will become "hot" (high in THC) thereby rendering the crop illegal under the 2018 Farm Bill. However, there are many factors that contribute to the amount of THC a plant may produce. This article examines and refutes the misconception of cross-pollination increasing THC levels by highlighting several methods of how THC may become high in a given hemp crop.

Exploiting Beneficial Pseudomonas spp. for Cannabis Production

Among the oldest domesticated crops, cannabis plants (Cannabis sativa L., marijuana and hemp) have been used to produce food, fiber, and drugs for thousands of years. With the ongoing legalization of cannabis in several jurisdictions worldwide, a new high-value market is emerging for the supply of marijuana and hemp products. This creates unprecedented challenges to achieve better yields and environmental sustainability, while lowering production costs. In this review, we discuss the opportunities and challenges pertaining to the use of beneficial Pseudomonas spp. bacteria as crop inoculants to improve productivity. The prevalence and diversity of naturally occurring Pseudomonas strains within the cannabis microbiome is overviewed, followed by their potential mechanisms involved in plant growth promotion and tolerance to abiotic and biotic stresses. Emphasis is placed on specific aspects relevant for hemp and marijuana crops in various production systems. Finally, factors likely to influence inoculant efficacy are provided, along with strategies to identify promising strains, overcome commercialization bottlenecks, and design adapted formulations. This work aims at supporting the development of the cannabis industry in a sustainable way, by exploiting the many beneficial attributes of Pseudomonas spp.

Assembly and potential transmission of the lens culinaris seed microbiome

Soil is an important source of bacteria and fungi for the plant, but seeds can also provide microbial inocula through heritable or stochastic assembly. Seed-associated microbial communities can potentially interact with the host plant through multiple generations. Here, we assessed the impact of two different soil types on the seed microbiome assembly of seven lentil (Lens culinaris) genotypes under environmentally controlled conditions and examined the vertical transmission of bacterial communities from seed to seed across two generations. Bulk soil microbiomes and seed microbiomes were characterized using high-throughput amplicon sequencing of the bacterial 16S rRNA gene. Our results revealed that bacterial communities in the two soils differed significantly and that bacterial communities associated with seeds were significantly impacted by genotype (15%) in one of the soils. Co-occurrence of amplicon sequence variants (ASVs) between generations suggests members of the genera Cutibacterium, Methylobacterium, Sphingomonas, Streptococcus, and Tepidimonas are transmitted and preserved in lentil genotypes irrespective of the soil in which they were grown. Increasing our knowledge of how microbial communities carried by seeds are assembled, transmitted, and preserved offers a promising way for future breeding programs to consider microbial communities when selecting for more resilient and productive cultivars.

Microbiome of Field Grown Hemp Reveals Potential Microbial Interactions With Root and Rhizosphere Soil

Hemp (Cannabis sativa L.) is a crop bred and grown for the production of fiber, grain, and floral extracts that contribute to health and wellness. Hemp plants interact with a myriad of microbiota inhabiting the phyllosphere, endosphere, rhizoplane, and rhizosphere. These microbes offer many ecological services, particularly those of below ground biotopes which are involved in nutrient cycling, uptake, and alleviating biotic and abiotic stress. The microbiota communities of the hemp rhizosphere in the field are not well documented. To discover core microbiota associated with field grown hemp, we cultivated single C. sativa cultivar, “TJ’s CBD,” in six different fields in New York and sampled hemp roots and their rhizospheric soil. We used Illumina MiSeq amplicon sequencing targeting 16S ribosomal DNA of bacteria and ITS of fungi to study microbial community structure of hemp roots and rhizospheres. We found that Planctobacteria and Ascomycota dominated the taxonomic composition of hemp associated microbial community. We identified potential core microbiota in each community (bacteria: eight bacterial amplicon sequence variant – ASV, identified as Gimesia maris, Pirellula sp. Lacipirellula limnantheis, Gemmata sp. and unclassified Planctobacteria; fungi: three ASVs identified as Fusarium oxysporum, Gibellulopsis piscis, and Mortierella minutissima). We found 14 ASVs as hub taxa [eight bacterial ASVs (BASV) in the root, and four bacterial and two fungal ASVs in the rhizosphere soil], and 10 BASV connected the root and rhizosphere soil microbiota to form an extended microbial communication in hemp. The only hub taxa detected in both the root and rhizosphere soil microbiota was ASV37 (Caulifigura coniformis), a bacterial taxon. The core microbiota and Network hub taxa can be studied further for biocontrol activities and functional investigations in the formulation of hemp bioinoculants. This study documented the microbial diversity and community structure of hemp grown in six fields, which could contribute toward the development of bioinoculants for hemp that could be used in organic farming.

Compartment Niche Shapes the Assembly and Network of Cannabis sativa-Associated Microbiome

Interactions between plants and microbes may promote the growth of plants and regulate the production of secondary metabolites. Hemp (Cannabis sativa) is an annual herb and an important commercial crop. However, the assembly and network of hemp-associated microbiomes inhabiting in soil and plant compartments have not been comprehensively understood. This work investigated the assembly and network of bacterial and fungal communities living in soils (bulk and rhizosphere) and plant compartments (root, stem, leaf, and flower) of four hemp ecotypes cultivated in the same habitat. Microbiome assembly was predominantly shaped by compartment niche. Microbial alpha diversity was the highest in soil, continually decreased from root to flower. Core bacterial genera Pseudomonas, Bacillus, Rhizobium, Planococcus, and Sphingomonas were mostly enriched in aerial endosphere niches; Clitopilus, Plectosphaerella, and Mortierella were enriched in belowground endosphere. Microbial network complexity and connectivity decreased from root to flower. According to source tracking analysis, hemp microbiota primarily originated from soil and were subsequently filtered in different plant compartments. This work provides details on hemp-associated microbiome along the soil-plant continuum and a comprehensive understanding of the origin and transmission mode of endophytes in hemp.

Cannabis Glandular Trichomes: A Cellular Metabolite Factory

Cannabis has been legalized for recreational use in several countries and medical use is authorized in an expanding list of countries; markets are growing internationally, causing an increase in demand for high quality products with well-defined properties. The key compounds of Cannabis plants are cannabinoids, which are produced by stalked glandular trichomes located on female flowers. These trichomes produce resin that contains cannabinoids, such as tetrahydrocannabinolic acid and cannabidiolic acid, and an array of other secondary metabolites of varying degrees of commercial interest. While growers tend to focus on improving whole flower yields, our understanding of the "goldmines" of the plant - the trichomes - is limited despite their being the true source of revenue for a multi-billion-dollar industry. This review aims to provide an overview of our current understanding of cannabis glandular trichomes and their metabolite products in order to identify current gaps in knowledge and to outline future research directions.

Emerging diseases of Cannabis sativa and sustainable management

Cultivation of cannabis plants (Cannabis sativa L., marijuana) has taken place worldwide for centuries. In Canada, legalization of cannabis in October 2018 for the medicinal and recreational markets has spurned interest in large-scale growing. This increased production has seen a rise in the incidence and severity of plant pathogens, causing a range of previously unreported diseases. The objective of this review is to highlight the important diseases currently affecting the cannabis and hemp industries in North America and to discuss various mitigation strategies. Progress in molecular diagnostics for pathogen identification and determining inoculum sources and methods of pathogen spread have provided useful insights. Sustainable disease management approaches include establishing clean planting stock, modifying environmental conditions to reduce pathogen development, implementing sanitation measures, and applying fungal and bacterial biological control agents. Fungicides are not currently registered for use and hence there are no published data on their efficacy. The greatest challenge remains in reducing microbial loads (colony-forming units) on harvested inflorescences (buds). Contaminating microbes may be introduced during the cultivation and postharvest phases, or constitute resident endophytes. Failure to achieve a minimum threshold of microbes deemed to be safe for utilization of cannabis products can arise from conventional and organic cultivation methods, or following applications of beneficial biocontrol agents. The current regulatory process for approval of cannabis products presents a challenge to producers utilizing biological control agents for disease management. © 2021 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cannabinoids Accumulation in Hemp (Cannabis sativa L.) Plants under LED Light Spectra and Their Discrete Role as a Stress Marker

Hemp adaptability through physiological and biochemical changes was studied under 10 LED light spectra and natural light in a controlled aeroponic system. Light treatments were imposed on 25 days aged seedlings for 16 h daily (300 µmol m-2 s-1) for 20 days. Plant accumulated highest Cannabidiol (CBD) in R7:B2:G1 light treatment, with relatively higher photosynthetic rate and lower reactive oxygen species, total phenol content, total flavonoid content, DPPH radical scavenging capacity, and antioxidant enzymatic activities. Tetrahydrocannabinol (THC) also accumulated at a higher level in white, R8:B2, and R7:B2:G1 light with less evidence of stress-modulated substances. These results indicated that CBD and THC have no or little relation with light-mediated abiotic stress in hemp plants. On the contrary, Tetrahydrocannabinolic acid (THCA) was accumulated higher in R6:B2:G1:FR1 and R5:B2:W2:FR1 light treatment along with lower photosynthetic rate and higher reactive oxygen species, total phenol content, total flavonoid content, DPPH radical scavenging capacity, and antioxidant enzymatic activities. However, Cannabidiolic acid (CBDA) was accumulated higher in R6:B2:G1:FR1 light treatment with higher stress-modulated substances and lower physiological traits. CBDA was also accumulated higher in R8:B2 and R7:B2:G1 light treatments with less evidence of stress-modulated substances. Besides, Greenlight influenced CBD and CBDA synthesis where FR and UV-A (along with green) play a positive and negative role in this process. Overall, the results indicated that the treatment R7:B2:G1 enhanced the medicinal cannabinoids most, and the role of THCA as a stress marker is more decisive in the hemp plant than in other cannabinoids under attributed light-mediated stress.

The Microbiome of the Medicinal Plants Achillea millefolium L. and Hamamelis virginiana L

In the recent past many studies investigated the microbiome of plants including several medicinal plants (MP). Microbial communities of the associated soil, rhizosphere and the above-ground organs were included, but there is still limited information on their seasonal development, and in particular simultaneous investigations of different plant organs are lacking. Many studies predominantly addressed either the prokaryotic or fungal microbiome. A distinction of epi- and endophytic communities of above-ground plant organs has rarely been made. Therefore, we conducted a comprehensive investigation of the bacterial and fungal microbiome of the MP Achillea millefolium and studied the epi- and endophytic microbial communities of leaves, flower buds and flowers between spring and summer together with the microbiome of the associated soil at one location. Further, we assessed the core microbiome of Achillea from four different locations at distances up to 250 km in southern Germany and Switzerland. In addition, the bacterial and fungal epi- and endophytic leaf microbiome of the arborescent shrub Hamamelis virginiana and the associated soil was investigated at one location. The results show a generally decreasing diversity of both microbial communities from soil to flower of Achillea. The diversity of the bacterial and fungal endophytic leaf communities of Achillea increased from April to July, whereas that of the epiphytic leaf communities decreased. In contrast, the diversity of the fungal communities of both leaf compartments and that of epiphytic bacteria of Hamamelis increased over time indicating plant-specific differences in the temporal development of microbial communities. Both MPs exhibited distinct microbial communities with plant-specific but also common taxa. The core taxa of Achillea constituted a lower fraction of the total number of taxa than of the total abundance of taxa. The results of our study provide a basis to link interactions of the microbiome with their host plant in relation to the production of bioactive compounds.

Endophytic Fungal Community of Tobacco Leaves and Their Potential Role in the Formation of "Cherry-Red" Tobacco

"Cherry-red" tobacco is the superior variant of tobacco, appearing with the apperance of red dapples on cured leaves due to the demethylation of nicotine to nornicotine during maturation and curing. Fungi are known to have the capacity to convert nicotine to nornicotine. However, an endophytic fungal community of "cherry-red" tobacco has never been reported to our best knowledge. Here, we sampled mature leaves from both "cherry-red" and ordinary tobacco at lower, center, and upper plant sections, and we analyzed the ITS diversity using high-throughput sequencing. Results revealed a significantly different fungal community of foliar endophyte in "cherry-red" and ordinary tobacco. In comparison to the ordinary control, higher diversity and a co-occurrence network complex were found in "cherry-red" samples, especially in the center and upper leaves, where the red dapples mainly emerged. More taxa were enriched in the "cherry-red" than ordinary tobacco leaves at all plant sections. In particular, Aspergillus, some strains of which are reported capable of converting nicotine to nornicotine, was specifically enriched in upper "cherry-red" tobacco leaves, which showed most red dapples after curing. A less robust network structure was detected in the "cherry-red" tobacco compared to ordinary tobacco. The nearest taxon index (NTI) and β NTI indicated that the local community structuration of tobacco endophytic fungi mainly driven by deterministic process, while the community turnover among plant sections was stochastic. In conclusion, our study provides the earliest information of endophytic fungal community in "cherry-red" tobacco leaf, and the community diversity, composition, and network features are synchronously varied with the appearance of red dapples, which is suggestive of their relationship to the formation of "cherry-red" tobacco.

Potential impacts of soil microbiota manipulation on secondary metabolites production in cannabis

BACKGROUND

Cannabis growing practices and particularly indoor cultivation conditions have a great influence on the production of cannabinoids. Plant-associated microbes may affect nutrient acquisition by the plant. However, beneficial microbes influencing cannabinoid biosynthesis remain largely unexplored and unexploited in cannabis production.

OBJECTIVE

To summarize study outcomes on bacterial and fungal communities associated with cannabis using high-throughput sequencing technologies and to uncover microbial interactions, species diversity, and microbial network connections that potentially influence secondary metabolite production in cannabis.

MATERIALS AND METHOD

A mini review was conducted including recent publications on cannabis and their associated microbiota and secondary metabolite production.

RESULTS

In this review, we provide an overview of the potential role of the soil microbiome in production of cannabinoids, and discussed that manipulation of cannabis-associated microbiome obtained through soil amendment interventions of diversified microbial communities sourced from natural forest soil could potentially help producers of cannabis to improve yields of cannabinoids and enhance the balance of cannabidiol (CBD) and tetrahydrocannabinol (THC) proportions.

CONCLUSION

Cannabis is one of the oldest cultivated crops in history, grown for food, fiber, and drugs for thousands of years. Extension of genetic variation in cannabis has developed into wide-ranging varieties with various complementary phenotypes and secondary metabolites. For medical or pharmaceutical purposes, the ratio of CBD to THC is key. Therefore, studying soil microbiota associated with cannabis and its potential impact on secondary metabolites production could be useful when selecting microorganisms as bioinoculant agents for enhanced organic cannabinoid production.

Host specific endophytic microbiome diversity and associated functions in three varieties of scented black rice are dependent on growth stage

The compositional and functional role of the endophytic bacterial community, associated with black scented rice, in correlation with its antioxidant property has been elucidated. Community dissimilarity analysis confirmed the overlapping of community in shoot and root tissues at the young stage, but not in mature plants. Proteobacteria was the most abundant phylum, in which Agrobacterium, Pleomorphomonas, Bradyrhizobium, Novasphingobium, Caulobacter were the most abundant genera, followed by Cyanobacteria and Planctomycetes in all three different varieties of the black rice. The antioxidant activity of mature plants was found to be higher in comparison to young plants. Intrinsically, the relative abundance of Pleomorphomonas and Streptomyces was positively correlated with total phenol content, while Gemmata, unclassified Pirellulaceae, unclassified Stramenopiles positively correlated with total flavonoid content and negatively correlated with Free radical scavenging activity. Accordingly, functional metagenome analysis of the endophytic microbiome revealed that naringenin -3-dioxygenase and anthocyanidin 3-O-glucosyltransferase for phenylpropanoid (flavonoid and anthocyanin) synthesis were abundant in the endophytic microbiome of mature plants. Specific enrichment of the antioxidant producing genes in the mature plant endophytic microbiome was assigned to some bacteria such as Streptomyces, Pantoea which might have contributed to the common pathway of flavonoid synthesis. The genomes of endophytic isolates Kluyvera sp.PO2S7, Bacillus subtilis AMR1 and Enterobacter sp. SES19 were sequenced and annotated, and were found to have genes for phenylpropanoid synthesis in their genomes.

Cannabinoids and Terpenes: How Production of Photo-Protectants Can Be Manipulated to Enhance Cannabis sativa L. Phytochemistry

Cannabis sativa L. is cultivated for its secondary metabolites, of which the cannabinoids have documented health benefits and growing pharmaceutical potential. Recent legal cannabis production in North America and Europe has been accompanied by an increase in reported findings for optimization of naturally occurring and synthetic cannabinoid production. Of the many environmental cues that can be manipulated during plant growth in controlled environments, cannabis cultivation with different lighting spectra indicates differential production and accumulation of medically important cannabinoids, including Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD), and cannabigerol (CBG), as well as terpenes and flavonoids. Ultraviolet (UV) radiation shows potential in stimulating cannabinoid biosynthesis in cannabis trichomes and pre-harvest or post-harvest UV treatment merits further exploration to determine if plant secondary metabolite accumulation could be enhanced in this manner. Visible LED light can augment THC and terpene accumulation, but not CBD. Well-designed experiments with light wavelengths other than blue and red light will provide more insight into light-dependent regulatory and molecular pathways in cannabis. Lighting strategies such as subcanopy lighting and varied light spectra at different developmental stages can lower energy consumption and optimize cannabis PSM production. Although evidence demonstrates that secondary metabolites in cannabis may be modulated by the light spectrum like other plant species, several questions remain for cannabinoid production pathways in this fast-paced and growing industry. In summarizing recent research progress on light spectra and secondary metabolites in cannabis, along with pertinent light responses in model plant species, future research directions are presented.

Strategies to Modulate Specialized Metabolism in Mediterranean Crops: From Molecular Aspects to Field

Plant specialized metabolites (SMs) play an important role in the interaction with the environment and are part of the plant defense response. These natural products are volatile, semi-volatile and non-volatile compounds produced from common building blocks deriving from primary metabolic pathways and rapidly evolved to allow a better adaptation of plants to environmental cues. Specialized metabolites include terpenes, flavonoids, alkaloids, glucosinolates, tannins, resins, etc. that can be used as phytochemicals, food additives, flavoring agents and pharmaceutical compounds. This review will be focused on Mediterranean crop plants as a source of SMs, with a special attention on the strategies that can be used to modulate their production, including abiotic stresses, interaction with beneficial soil microorganisms and novel genetic approaches.

Linking Plant Secondary Metabolites and Plant Microbiomes: A Review

Plant secondary metabolites (PSMs) play many roles including defense against pathogens, pests, and herbivores; response to environmental stresses, and mediating organismal interactions. Similarly, plant microbiomes participate in many of the above-mentioned processes directly or indirectly by regulating plant metabolism. Studies have shown that plants can influence their microbiome by secreting various metabolites and, in turn, the microbiome may also impact the metabolome of the host plant. However, not much is known about the communications between the interacting partners to impact their phenotypic changes. In this article, we review the patterns and potential underlying mechanisms of interactions between PSMs and plant microbiomes. We describe the recent developments in analytical approaches and methods in this field. The applications of these new methods and approaches have increased our understanding of the relationships between PSMs and plant microbiomes. Though the current studies have primarily focused on model organisms, the methods and results obtained so far should help future studies of agriculturally important plants and facilitate the development of methods to manipulate PSMs-microbiome interactions with predictive outcomes for sustainable crop productions.

Medicinal Plants and Their Bacterial Microbiota: A Review on Antimicrobial Compounds Production for Plant and Human Health

Medicinal plants (MPs) have been used since antiquity in traditional and popular medicine, and they represent a very important source of bioactive molecules, including antibiotic, antiviral, and antifungal molecules. Such compounds are often of plant origin, but in some cases, an origin or a modification from plant microbiota has been shown. Actually, the research continues to report the production of bioactive molecules by plants, but the role of plant–endophytic interaction is emerging. Classic examples are mainly concerned with fungal endophytes; however, it has been recently shown that bacterial endophytes can also play an important role in influencing the plant metabolism related to the synthesis of bioactive compounds. In spite of this, a deep investigation on the power of MP bacterial endophytes is lacking. Here, an overview of the studies on MP bacterial microbiota and its role in the production of plant antimicrobial compounds contributing to prime host defense system and representing a huge resource for biotech and therapeutic applications is provided.

Expression of Putative Defense Responses in Cannabis Primed by Pseudomonas and/or Bacillus Strains and Infected by Botrytis cinerea

Cannabis (Cannabis sativa L.) offers many industrial, agricultural, and medicinal applications, but is commonly threatened by the gray mold disease caused by the fungus Botrytis cinerea. With few effective control measures currently available, the use of beneficial rhizobacteria represents a promising biocontrol avenue for cannabis. To counter disease development, plants rely on a complex network of inducible defense pathways, allowing them to respond locally and systemically to pathogens attacks. In this study, we present the first attempt to control gray mold in cannabis using beneficial rhizobacteria, and the first investigation of cannabis defense responses at the molecular level. Four promising Pseudomonas (LBUM223 and WCS417r) and Bacillus strains (LBUM279 and LBUM979) were applied as single or combined root treatments to cannabis seedlings, which were subsequently infected by B. cinerea. Symptoms were recorded and the expression of eight putative defense genes was monitored in leaves by reverse transcription quantitative polymerase chain reaction. The rhizobacteria did not significantly control gray mold and all infected leaves were necrotic after a week, regardless of the treatment. Similarly, no systemic activation of putative cannabis defense genes was reported, neither triggered by the pathogen nor by the rhizobacteria. However, this work identified five putative defense genes (ERF1, HEL, PAL, PR1, and PR2) that were strongly and sustainably induced locally at B. cinerea's infection sites, as well as two stably expressed reference genes (TIP41 and APT1) in cannabis. These markers will be useful in future researches exploring cannabis defense pathways.