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Proceedings of Past Forest Nursery Association Meetings:

Status on Commercial Development of Burkholderia cepacia for Biological Control of Fungal Pathogens and Growth Enhancement of Conifer Seedlings for a Global Market
M. S. Reddy
1996: New England, CT
Forestry is an extremely important industry in many countries. With an increasing demand for forest products, many forest companies and government organizations have turned toward more intensive management practices to increase productivity of forest lands. Seedling losses occur in conifer nurseries as well as on reforestation sites despite of the best efforts employed by nurserymen and foresters in disease control and site preparation. Fungal pathogens such as Fusarium, Pythium, Rhizoctonia, Cylindrocarpon, Cylindrocladium and Botrytis are widespread causing seedling losses in nurseries. These pests are also transported to field sites where they continue to cause economic losses by killing, stunting, or deforming transplanted seedlings. One of the most acceptable and environmentally-conscious approaches to solving these problems is the use of a naturally occurring microbial inoculant. We have assessed a microbial culture collection of approximately 500 strains of diverse origin for biological control of fungal pathogens and/or plant growth promotion of various types of conifer spp. under laboratory and greenhouse conditions. Variable results were obtained for most of the strains tested, except for one isolate which is a Burkholderia cepacia, strain Ral-3. For further product development, a proprietary liquid formulation was developed and used in product efficacy trials as a seed or root dip treatment on several conifer species at several locations in western Canada and the Pacific Northwest, USA. Storage stability of strain Ral-3 in commercial packages was maintained, with a viable population of about log 8-9 cfu/ml for over a year when stored at 5-201C. In most trials, strain Ral-3 showed significant suppressive effects on various soilborne fungal pathogens. Significant growth responses including survival, root and shoot biomass, height and caliper were observed. Strain Ral-3 is compatible with many seed treatment fungicides and with other cultural practices currently used in the forestry industry. Strain Ral-3 is also an active and aggressive rhizosphere colonizer of many conifer spp., such as white spruce, Douglas-fir, jack pine, Scots pine, cedar, and western hemlock. Possible mode of action and other data related to regulatory requirements will be discussed.

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