Location: Horticultural Crops Research
2012 Annual Report
Forest nurseries of the Pacific Northwest USA were surveyed for the presence of soilborne pathogens and eight Pythium spp. pathogenic to Douglas-fir seedlings were found. Reduced-rate alternative fumigant treatments were identified that were as effective as methyl bromide at disease and weed control in forest nursery field studies. Aerated steam, irrigation management, and certain fungicides were also effective for the control of soilborne pathogens. These findings are significant because they provide economically viable alternatives to methyl bromide for disease control and their implementation can reduce emissions through lower rates of applied fumigants.
The host status of blueberry varieties to plant-parasitic nematodes and the impact of stubby root nematode (Paratricodorus renifer) on blueberry were determined. Blueberry varieties with genetic backgrounds including Vaccinium corymbosum and V. angustifolium were excellent hosts for stubby root nematode, but V. ashei was a poor host for this nematode. In field microplots, berry yield was reduced by at least 25% by stubby root nematode. Knowledge of a resistance mechanism to plant-parasitic nematodes can lead to the development of nematode resistant blueberry cultivars. On grape, another plant-parasitic nematode, ring nematode (Mesocriconema xenoplax), initially caused decreased root growth, but its above-ground impact on plant productivity was not apparent until the third year of a four-year study. The apparent ring nematode resistance of the rootstock 101-14 broke down in year three, with only the rootstock 420A remaining highly resistant to the nematode. Growers will use this information to select rootstocks for planting and to direct the timing of management practices to minimize the impact of ring nematode on vine establishment and productivity.
We devised an inoculation assay and used it to assess susceptibility of blueberry varieties to Pseudomonas syringae. We also confirmed that growing ornamentals such as lilac in plastic shelters provided excellent control of bacterial blight caused by P. syringae and demonstrated that this control is due primarily to reduced leaf wetness, not frost protection as previously thought. Towards our objective of developing knowledge of mechanisms of biological control of plant diseases, we completed a project comparing genomic sequences of ten biological control strains of Pseudomonas spp., and identified genes for the biosynthesis of novel antibiotics and insect toxins. Using genomic mining, we discovered two new natural products and demonstrated the anti-fungal activities of these compounds. We developed a microarray for the biological control organism (Pseudomonas protegens strain Pf-5) and used it to identify genes expressed by the bacterium on plants as well as factors controlling the expression of genes required for biological control. This information is allowing us to use directed strategies to improve the reliability of biological control for agriculture.
Zasada, I.A., Walters, T.W., Pinkerton, J. 2011. Post-Plant nematicides for the control of root lesion nematode in red raspberry. HortTechnology. 20:856-862.
Zasada, I.A., Weiland, G.E., Reed, R.L., Stevens, J.F. 2011. Activity of meadowfoam (Limnanthes alba) seed meal glucolimnanthin degradation products against soilborne pathogens. Journal of Agricultural and Food Chemistry. 60:339-345.
Meyer, S.L., Zasada, I.A., Orisajo, S.B., Morra, M.J. 2011. Mustard seed meal mixtures: management of Meloidogyne incognita on pepper and potential phytotoxicity. Journal of Nematology. 43(1):7-15.
Kroese, D., Zasada, I.A., Ingham, R.E. 2011. Comparison of Meldola’s Blue staining and hatching assay with potato root diffusate for assessment of Globodera sp. egg viability. Journal of Nematology. 43(3/4):182-186.
Weiland, G.E., Leon, A.L., Edmonds, R.L., Littke, W.R., Browning, J.E., Rose, R., Cherry, M., Davis, E.A., Beck, B.R., Miller, T. 2011. The effects of methyl bromide alternatives on soil and seedling microbial populations, weeds, and seedling morphology in Oregon and Washington forest tree nurseries. Canadian Journal of Forest Research. 41(8):1885-1896.
Subramoni, S., Gonzalez, J.F., Johnson, A., Pechy-Tarr, M., Rochat, L., Paulsen, I., Loper, J.E., Keel, C., Venturi, V. 2011. Bacterial subfamily of LuxR regulators that respond to plant compounds. Applied and Environmental Microbiology. 77(13):4579-4588.
Lim, C., Hassan, K.H., Tetu, S., Loper, J.E., Paulsen, I. 2012. The effect of iron limitation on the transcriptome and proteome of Pseudomonas fluorescens Pf-5. PLoS One. 7(6):e39139.
Kidarsa, T.A., Goebel, N.C., Zabriskie, T., Loper, J.E. 2011. Phloroglucinol mediates crosstalk between the pyoluteorin and 2,4-diacetylphloroglucinol biosynthetic pathways in Pseudomonas fluorescens Pf-5. Molecular Microbiology. 81(2):395-414.
Loper, J.E., Hassan, K.A., Mavrodi, D., Davis, E.W., Lim, C., Shaffer, B.T., Elbourne, L.H., Stockwell, V.O., Hartney, S.L., Breakwell, K., Henkels, M.D., Tetu, S.G., Rangel, L.I., Kidarsa, T.A., Wilson, N.L., Van Mortel, J., Song, C., Blumhagen, R., Radune, D., Hostetler, J.B., Brinkac, L.M., Durkin, A., Kluepfel, D.A., Wechter, W.P., Anderson, A.J., Kim, Y., Pierson Iii, L.S., Pierson, E.A., Lindow, S.E., Raaijmakers, J.M., Weller, D.M., Thomashow, L.S., Allen, A.E., Paulsen, I.I. 2012. Comparative genomics of plant-associated Pseudomonas spp.: Insights into diversity and inheritance of traits involved in multitrophic interactions. PLoS Genetics. 8(7):e1002784.
Walters, T.A., Zasada, I.A., Pinkerton, J.N., Koch, C. 2012. Host status and damage potential of Paratrichodorus renifer and Pratylenchus penetrans (Nematoda) to blueberry (Vaccinium spp.). Canadian Journal of Plant Pathology. 34(2):277-282.