PATHOGENS AND OTHER FUNGI IN GROWING MEDIA CONSTITUENTS
With the increasing availability of composted and other organic alternatives to peat in the UK and continuing encouragement to use them, growing media manu¬facturers have begun to seek assurance that every substrate they use, including peat, is free of plant and human pathogens. This study was initiated to validate and exploit the use a state-of-the-art nucleic acid-based technique to investigate the diversity of fungal species in a range of substrates representing peat (13 samples), composted green waste (9), woodfibre (6), coir (6) and bark (4). In all twenty-nine different species of fungi were identified in the 38 substrates tested, of which the majority (Aspergillus, Chaetomium, Mortierella, Mucor, Penicillium, Verticillium and other species) were benign saprotrophic organisms. Beneficial Trichoderma species (T. asperellum, T. harzianum and T. viride) were present in nine samples, mostly peats. Only two of the samples contained fungi that might be regarded as a potential threat to plant health, Fusarium oxypsorum f.sp. melonis, a pathogen of melons, and a species of Rhizoctonia pathogenic to barley and lupins. R. solani was demonstrably absent in all and so was the clubroot organism, Plasmodiophora brassicae, whose presence was also rigorously investigated using a sensitive antibody and PCR-based technique. This study has shown that modern molecular techniques can be used to provide a comprehensive assessment of contamination of growing media constituents, particularly by fungi such as F. oxysporum and other commercially significant organisms such as the plant pathogen P. brassicae. As a result of this study the technique is now being offered commercially.
Waller, P.L., Thornton, C.R., Farley, D. and Groenhof, A. (2008). PATHOGENS AND OTHER FUNGI IN GROWING MEDIA CONSTITUENTS. Acta Hortic. 779, 361-366
bark, coir, compost, Fusarium, peat, Plasmodiophora, Rhizoctonia, Trichoderma