Organically grown cannabis (Cannabis sativa L.) plants contain a diverse range of culturable epiphytic and endophytic fungi in inflorescences and stem tissues

Abstract

We investigated the diversity of fungal species present on inflorescences as epiphytes and in stem tissues as endophytes in flowering plants of cannabis grown organically in British Columbia during 2019-2021. Fresh and dried inflorescence samples were obtained at various times during production while stems were obtained at harvest. Fungal species in the air were assessed by exposing Petri dishes containing potato dextrose agar + streptomycin sulphate for 1 hr in the growing environment while soil samples were dilution-plated to assess soil fungal diversity. Colonies were identified from PCR-derived sequences of the ITS1-5.8S- ITS2 region of rDNA. Twenty-nine species in 26 genera were recovered from inflorescences and 17 species in 11 genera originated from stem tissues. Approximately 96 % of species found on inflorescences were present in air and 45 % were present in organic soil. The fungi comprised plant pathogens, saprophytes, and opportunistic human pathogens. A large proportion of the species found in air and soil in organic facilities are present on cannabis inflorescences, where they may increase total colony- forming units and negatively affect product quality. Some species could contribute to allergies or secondary infections in humans. The potential benefits of endophytes within organically grown cannabis plants remain unexplored.

Challenges to Cannabis sativa Production from Pathogens and Microbes—The Role of Molecular Diagnostics and Bioinformatics

“…The universal eukaryotic primers also confirmed the presence of Trichoderma asperellum originating from root tissues and Penicillium olsonii originating from stem tissues. The former is a biological control agent that is frequently applied during greenhouse cannabis production, while the latter is a naturally occurring endophyte found in cannabis stems [ 2 , 12 ]. Cannabis DNA was also amplified with this primer set, which was differentiated by its different molecular weight fragment size and unique sequence that differentiated it from the respective pathogens.…”

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

“…Another aspect of potential microbial antagonism against fungal pathogens infecting cannabis that requires research is the diverse microflora that can be present in organic soils compared to conventional hydroponic cultivation. Punja and Scott [ 87 ] reported that a diverse range of microbes were recovered from cannabis inflorescences grown in organic soil compared to the cocofibre medium commonly used in hydroponic cannabis production. These communities were comprised of pathogenic, saprophytic, and beneficial microbes.…”

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

“…A similar study has not been conducted in hemp. In addition, the presence of airborne fungal contaminants during harvesting of cannabis and hemp and those that are present in the cultivation environment can be of potential concern for human health ( Martyny et al, 2013 ; Vanhove et al, 2018 ; Root et al, 2020 ; Punja, 2021c ; Punja and Scott, 2023 ). Lastly, a few fungal species of cannabis and hemp can directly impact human health by causing tissue infections, resulting in mycoses for immunocompromised individuals (see Section 3.1).…”

“…b Mycotoxin potential: (−) Unknown; (+) Low; (++) Medium; (+++); C High Relative abundance was estimated based on the relative frequency of occurrence of colonies of the particular species among the total Petri dishes assayed. Adapted from Punja and Scott (2023) .…”

“…Furthermore, plant organs (roots, stems, leaves, and flowers) vary in the community structure of their mycobiomes and plant pathogens ( Barnett et al, 2020 ; Comeau et al, 2020 ). For example, plants grown in soil and soilless media used for indoor production may harbor different endophytic and phytopathogenic fungi ( Punja and Scott, 2023 ). The origins of these fungi can be traced back to the growing medium used, source of plant propagation materials, or are present externally in the ambient environment.…”