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Seedborne fusarium and root colonization of container-grown douglas-fir seedlings Neumann, Melody J.

Abstract

The role of seedborne Fusarium in root colonization of container-grown Douglas-fir seedlings was studied in two coastal Douglas-fir seedlots; one contaminated with Fusarium and the other with minimal Fusarium. Seedlots were treated using either a standing water imbibition, or a running water imbibition with a post-stratification hydrogen peroxide sanitation treatment. The sanitation treatment significantly reduced the number of Fusarium-contaminated seeds. Seedlings were grown in an operational conifer nursery and seedling infection and root colonization by Fusarium was assessed throughout the growing season. The number of seedlings with Fusarium root infections increased throughout the season, and remained highest for the standing water imbibition treatment of the contaminated seedlot. Seedborne Fusarium was an important source of inoculum in one of the two years of the study. Other sources of inoculum may have been pallets or debris, but planting mix and irrigation water used in the study did not appear to contain Fusarium. Seed sanitation was associated with a significant increase in average height, root collar diameter, and shoot and root dry weight for the seedlings from the contaminated seedlot but not for the uncontaminated seedlot. Contamination of seed by Fusarium during cone and seed processing was also investigated.

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