Journal:Pathogens and molds affecting production and quality of Cannabis sativa L.
| Full article title | Pathogens and molds affecting production and quality of Cannabis sativa L. |
|---|---|
| Journal | Frontiers in Plant Science |
| Author(s) | Punja, Zamir K.; Collyer, Danielle; Scott, Cameron; Lung, Samantha; Holmes, Janesse; Sutton, Darren |
| Author affiliation(s) | Simon Fraser University |
| Primary contact | Email: punja at sfu dot ca |
| Editors | Smith, Donald L. |
| Year published | 2019 |
| Volume and issue | 10 |
| Article # | 1120 |
| DOI | 10.3389/fpls.2019.01120 |
| ISSN | 1664-462X |
| Distribution license | Creative Commons Attribution 4.0 International |
| Website | https://www.frontiersin.org/articles/10.3389/fpls.2019.01120/full |
| Download | https://www.frontiersin.org/articles/10.3389/fpls.2019.01120/pdf (PDF) |
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Abstract
Plant pathogens infecting marijuana (Cannabis sativa L.) plants reduce growth of the crop by affecting the roots, crown, and foliage. In addition, fungi (molds) that colonize the inflorescences (buds) during development or after harvest, and which colonize internal tissues as endophytes, can reduce product quality. The pathogens and molds that affect C. sativa grown hydroponically indoors (in environmentally controlled growth rooms and greenhouses) and field-grown plants were studied over multiple years of sampling. A polymerase chain reaction (PCR) assay using primers for the internal transcribed spacer region (ITS) of ribosomal DNA confirmed identity of the cultures. Root-infecting pathogens included those from the Fusarium genus (Fusarium oxysporum, Fusarium solani, and Fusarium brachygibbosum) and the Pythium genus (Pythium dissotocum, Pythium myriotylum, and Pythium aphanidermatum), which caused root browning, discoloration of the crown and pith tissues, stunting and yellowing of plants, and in some instances, plant death. On the foliage, powdery mildew, caused by Golovinomyces cichoracearum, was the major pathogen observed. On inflorescences, Penicillium bud rot (caused by Penicillium olsonii and Penicillium copticola), Botrytis bud rot (Botrytis cinerea), and Fusarium bud rot (F. solani, F. oxysporum) were present to varying extents. Endophytic fungi present in crown, stem, and petiole tissues included soil-colonizing and cellulolytic fungi, such as species of Chaetomium, Trametes, Trichoderma, Penicillium, and Fusarium. Analysis of air samples in indoor growing environments revealed that species of Penicillium, Cladosporium, Aspergillus, Fusarium, Beauveria, and Trichoderma were present. The latter two species were the result of the application of biocontrol products for control of insects and diseases, respectively. Fungal communities present in unpasteurized coconut (coco) fiber growing medium are potential sources of mold contamination on Cannabis plants. Swabs taken from greenhouse-grown and indoor buds pre- and post-harvest revealed the presence of Cladosporium and up to five species of Penicillium, as well as low levels of Alternaria species. Mechanical trimming of buds caused an increase in the frequency of Penicillium species, presumably by providing entry points through wounds or spreading endophytes from pith tissues. Aerial distribution of pathogen inoculum and mold spores and dissemination through vegetative propagation are important methods of spread, and entry through wound sites on roots, stems, and bud tissues facilitates pathogen establishment on Cannabis plants.
Keywords: diseases, plant pathogens, epidemiology, post-harvest molds, fungi, root infection, endophytes
Introduction
Cannabis sativa L., a member of the family Cannabaceae, is cultivated worldwide as hemp (for fiber, seed, and oil) and marijuana (referred to hereon as cannabis) for medicinal and psychotropic effects. The pathogens affecting production of hemp have been described and include fungal, bacterial, viral, and nematode species.[1][2] In contrast, the pathogens affecting cannabis have not been extensively studied, and the different growing environments, cultivation methods, as well as differences among the strains or genetic selections of hemp and cannabis can influence disease development. This requires that studies on the pathogens potentially affecting Cannabis plants be conducted so that methods to manage emerging diseases and molds can be developed. Cannabis plants are propagated from cuttings that are rooted and grown vegetatively, following which they are transferred to conditions of specific reduced lighting regimes (photoperiod) to induce flowering.[3] Flower buds are harvested, dried, and stored in vacuum-sealed bags or sealed plastic or glass containers prior to distribution. Fungal infection of roots can occur at any time during the production cycle, while colonization of flower buds generally occurs during the later stages of flower development and can be manifested as a pre-harvest or post-harvest bud rot. In addition, foliar pathogens may infect the plant at any stage during its production.
The objectives of this research were to determine the prevalence of root-infecting, foliar-infecting, and flower-infecting fungi affecting Cannabis plants grown in indoor environments, in greenhouses, and under field conditions to obtain a better understanding of the diseases affecting this plant. In addition, the incidence of molds in the growing environments, and on pre-harvest and post-harvest inflorescences, was assessed. Cultural methods for isolation, and morphological and molecular methods for identification, were used in this study. More than 22 different fungal and oomycete species and their associated effects on Cannabis plants grown indoors and outdoors are presented.
References
- ↑ McPartland, S.M. (1991). "Common names for diseases of Cannabis sativa L.". Plant Disease 75: 226–7.
- ↑ McPartland, J.M. (1996). "A review of Cannabis diseases". Journal of International Hemp Association 3 (1): 19–23. http://www.internationalhempassociation.org/jiha/iha03111.html.
- ↑ Small, E. (2017). Cannabis: A Complete Guide. CRC Press. ISBN 9781498761635.
Notes
This presentation is faithful to the original, with only a few minor changes to presentation. Some grammar and punctuation was cleaned up to improve readability. In some cases important information was missing from the references, and that information was added. The original article lists references in alphabetical order; this version lists them by order of appearance, by design.
