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United States Department of Agriculture

Agricultural Research Service

Title: Meadowfoam Seedmeal Inhibition of Soilborne Pathogenic and Mycorrhizal Fungi

Authors
item Linderman, Robert
item Deuel, W - FULL CIRCLE AG, INC.
item Marlow, Joseph
item Davis, E Anne

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: August 19, 2003
Publication Date: October 12, 2003
Citation: Linderman, R.G., Deuel, W.A., Marlow, J.L., Davis, E.A. 2003. Meadowfoam seedmeal inhibition of soilborne pathogenic and mycorrhizal fungi. Meeting Abstract.

Technical Abstract: Meadowfoam (Limnanthes alba) is grown in Oregon for its high quality seed oil. Meadowfoam seedmeal (MSM) remaining after oil extraction contains chemicals, such as glucosinolates, that may degrade to release byproducts inhibitory to weeds, insects, and soilborne pathogens. MSM in soil also has been shown to stimulate plant growth. The objectives of our studies were (1) to determine if MSM, alone or in combination with the oil, would have any effect on pathogenic soilborne fungi in vitro; and (2) to determine if there were any adverse effects on non-target beneficial arbuscular mycorrhizal (AM) fungi in soil. Combinations of meadowfoam oil and MSM, or MSM alone, were incorporated into agar media in Petri plates, and the pathogens inoculated to the agar surface. Colony diameter after 72 hr was compared to the non-amended control plates. In tests for volatile effects, MSM alone or incorporated into soil (4% by volume) was placed on one side of divided Petri plates and the pathogen inoculated on the opposite side. Colony diameter and sporulation of test pathogens was measured after several days of incubation. For tests on the effects on mycorrhiza formation, MSM was amended at three rates into an organic soil mix, into which marigold or onion plants, inoculated or not with the AM fungus Glomus intraradices, were planted and grown in the greenhouse for 10 weeks before assessing plant biomass and level of AM colonization. Mycelial growth of most fungal pathogens was inhibited by combinations of oil and MSM, as was sporulation by some Pythium and Phytophthora species. Amendment of soil with MSM enhanced growth of marigolds at 0.594 or 1.188 kg m-3, but inhibited growth at 1.782 kg m-3. AM formation on marigold or onion was inhibited at all rates tested, but additional tests indicated that the AM fungal inoculum was inhibited, not killed. Ground MSM alone incorporated into agar did not inhibit pathogen mycelial growth, but did inhibit production of oospores by Pythium irregulare and sporangia but not chlamydospores of Phytophthora ramorum. In vitro tests for volatile effects with MSM alone or mixed into soil showed that volatiles released from the MSM inhibited sporulation of P. ramorum. These results indicate that volatile or non-volatile compounds released from MSM could inhibit soilborne fungal pathogens, at least in vitro, but tests on plants in MSM-amended soils are needed to determine whether MSM can suppress the diseases they cause. The adverse effects of MSM on non-target mycorrhizae and the mode of action against AM fungi in soil remain problematic. Nonetheless, the potential for MSM amendment to soil or potting media for disease control deserves further research.

Last Modified: 10/22/2014
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