Figure 2.

Root-infecting pathogens on Cannabis sativa. (A) Symptoms of brown discoloration on the root system of indoor hydroponically grown plants. (B) Colonies of Fusarium oxysporum isolated from diseased roots in (A) growing on potato dextrose agar. (C) Colony of Pythium catenulatum isolated from diseased roots growing on potato dextrose agar. (D) Symptoms of natural crown infection on a field-grown cannabis plant caused by a combination of F. oxysporum, Fusarium brachygibbosum, and Pythium aphanidermatum. (E) The crown area of the infected plant shown in (D) is sunken, and there is visible mycelial growth on the surface. (F) Colony of Fusarium brachygibbosum isolated from diseased roots growing on potato dextrose agar. (G) Symptoms of plant collapse as a result of infection by P. aphanidermatum under a greenhouse environment. (H) Comparison of a noninoculated plant (left) with a plant wound-inoculated with spores of F. oxysporum (right) and grown in coco fiber substrate. Photo was taken 4 weeks after inoculation and shows stunting and yellowing of leaves. (I) Symptom of internal discoloration of the pith tissue in the upper 10 cm of the crown region of a plant grown indoors in coco fiber as a substrate and infected by F. oxysporum. Figures 2A, D, E, G reproduced from Can. J. Plant Pathol. 40(4) by permission.