Endophytes of industrial hemp (Cannabis sativa L.) cultivars: identification of culturable bacteria and fungi in leaves, petioles, and seeds

Abstract

Plant endophytes are a group of microorganisms that reside asymptomatically within the healthy living tissue. The diversity and molecular and biochemical characterization of industrial hemp-associated endophytes have not been previously studied. This study explored the abundance and diversity of culturable endophytes residing in petioles, leaves, and seeds of three industrial hemp cultivars, and examined their biochemical attributes and antifungal potential. A total of 134 bacterial and 53 fungal strains were isolated from cultivars Anka, CRS-1, and Yvonne. The number of bacterial isolates was similarly distributed among the cultivars, with the majority recovered from petiole tissue. Most fungal strains originated from leaf tissue of cultivar Anka. Molecular and phylogenetic analyses grouped the endophytes into 18 bacterial and 13 fungal taxa, respectively. The most abundant bacterial genera were Pseudomonas, Pantoea, and Bacillus, and the fungal genera were Aureobasidium, Alternaria, and Cochliobolus. The presence of siderophores, cellulase production, and phosphorus solubilization were the main biochemical traits. In proof-of-concept experiments, re-inoculation of tomato roots with some endophytes confirmed their migration to aerial tissues of the plant. Taken together, this study demonstrates that industrial hemp harbours a diversity of microbial endophytes, some of which could be used in growth promotion and (or) in biological control designed experiments.

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

“…Most of the above findings illustrate the use of endophytic bacteria isolated from plant species other than hemp or marijuana with the ability to trigger some physiological plant responses. Our laboratory, along with other researchers, has reported on the diversity of endogenous fungal and bacterial endophytes and the abundance of taxonomic groups in different tissues of hemp and marijuana with growth promotion capabilities (Table 1) and biological control potential ( Table 2) [81][82][83][84]87,96]. Some of these isolates were able to trigger the production of IAA-like molecules in the plant, reinforcing the notion that beneficial endophytes modulate plant development and growth through the production of phytohormones.…”

“…For example, the abundance number of fungal strains belonging to Aspergillus, Penicillium, Phoma, Rhizopus, Colletotrichum, Cladosporium, and Curvularia in leaf samples from Himachal Pradesh, India [83] was higher as compared to those in stems and petioles [83]. Similarly, the fungal strains Cochliobolus and Aureobasidium isolated from Canadian hemp samples were abundant in leaf tissue [81]. Leaf, twig, and bud tissues of Bedrocan BV Medicinal marijuana from the Netherlands were associated with endophytic communities belonging to the Penicillium species (predominantly, Penicillium copticola), Eupenicillium rubidurum, Chaetomium globosum, and Paecilomyces lilacinus [84].…”

“…The diversity of fungal and bacterial endophytes associated with different tissues of hemp and marijuana sampled from various geographic and ecological regions is listed in Figure 1. Almost all of the nonsymbiotic fungal endophytes reported by several studies belonged to the Ascomycetes, except for two studies that reported the presence of strains belonging to the Basidiomycetes, such as Irpex, Cryptococcus [81] and Schizophyllum commune [82]. Depending on the geographical region, the abundance of fungal endophytes associated with cannabis tissues varied.…”

“…were found in marijuana stem tissues [83]. Moreover, strains belonging to Alternaria, Cryptococcus, Aspergillus, Cladosporium, and Penicillium [81,83,85] were isolated from marijuana and hemp petioles, whereas Aureobasidium and Cladosporium were isolated from hemp seeds [81]. Intensive mycorrhization of hemp roots by the arbuscular mycorrhizal (AM) fungi, Diversispora sp., Funneliformis mosseae, Funneliformis geosporum, Glomus caledonium, and Glomus occultum enabled the plant to tolerate soils contaminated with phosphogypsum and sewage sludge, and responded positively regarding biomass production [86].…”

“…Namely, Bacillus licheniformis, Bacillus subtilis, Bacillus pumilus, and Bacillus megaterium formed the most abundant Gram-positive bacterial endophytes population in the leaf [81,88]. Strains of Pantoea and Staphylococcus were associated exclusively with cannabis petioles [81], while strains of Pantoea, Staphylococcus, Bacillus, and Enterobacter were isolated from the seed [81]. The most prominent isolated genera from roots included Acinetobacter, Chryseobacterium, Enterobacter, Microbacterium, and Pseudomonas [87].…”