Chaetomium globosum, a pathogen of hemp, Cannabis sativa
Chaffin, A.G., M. E. Dee, S. Boggess, R. N. Trigiano, E. C. Bernard, and K. D. Gwinn.  2019.  Phytopathology, Phytopathology 109:S2.121. American Phytopathological Society, Cleveland, OH. August 3-7.

Abstract:
In the United States, there is an unprecedented demand for Cannabis sativa with low levels of the psychoactive drug, tetrahydrocannabinol (THC), because of other medicinal compounds and fibers produced by the plant. Cultivation of hemp has been limited in the United States because of its close relationship to THC-containing varieties (i.e., marijuana), thus, little is known about its pathogens. Putative pathogens were isolated from symptomatic leaves of two greenhouse grown fiber varieties, Futura and Fedora. Four isolates were identified as Chaetomium globosum based on colony characteristics, and ascospore and perithecium morphology. Pathogen identification was confirmed by amplifying and sequencing the ITS region, which had a 100% nucleotide sequence identity with C. globosum (GenBank:HG423571.1). In detached leaf assays, original symptoms were duplicated on the two fiber varieties from which the original isolates were collected; similar symptoms were produced on another fiber variety, Delores. The pathogen was reisolated from leaves and grown in axenic culture. Greenhouse grown plants were inoculated on leaves with mycelial plugs, and original symptoms were duplicated on ‘Fedora’ and ‘Futura’, but not on ‘Wife’, a high CBD variety. The relationship between secondary metabolite concentrations and the lack of symptom development on ‘Wife’ in plants, and in subsequent detached leaf assays is unknown. Therefore, additional high CBD varieties will be tested.