Location: Horticultural Crops ResearchTitle: Identifying rates of meadowfoam (Limnanthes alba) seed meal needed for suppression of Meloidogyne hapla and Pythium irregulare in soil
|ERSAHIN, YURDAGUL - Cankiri Karatekin University|
|REED, RALPH - Oregon State University|
|STEVENS, JAN - Oregon State University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2014
Publication Date: 9/1/2014
Citation: Ersahin, Y.S., Weiland, G.E., Zasada, I.A., Reed, R.L., Stevens, J.F. 2014. Identifying rates of meadowfoam (Limnanthes alba) seed meal needed for suppression of Meloidogyne hapla and Pythium irregulare in soil. Plant Disease. 98(9):1253-1260.
Interpretive Summary: Soilborne pathogens and plant-parasitic nematodes are both serious pests of agricultural crops worldwide. Novel ways to manage these pests must be discovered to maintain crop productivity. To this end, we examined the efficacy of different rates of meadowfoam seed meal in soil for controlling the soilborne plant-parasitic nematode (Meloidogyne hapla) and pathogen (Pythium irregulare) and on plant health. We found that the seed meal needed to be mixed with 1% seed to produce compounds toxic to the two soilborne pests. Unfortunately, the rates that controlled these pests were also toxic to tomatoes, wheat, and cucumbers that were planted immediately into the treated soil. However, the toxic effect to these crops was eliminated by waiting several days before planting into treated soil; the toxic compounds had disappeared by that time. Finally, we determined that both soilborne pests were killed within two hours after soil was treated with seed meal and seed. This research is significant because it establishes the use of a by- product of the oilseed industry, meadowfoam seed meal, as a naturally-occurring pesticide for plant-parasitic nematodes and pathogens.
Technical Abstract: Meadowfoam (Limnanthes alba) is a commercial oilseed crop grown in Oregon. After extracting oil from seed, the remaining seed meal is rich in the secondary plant metabolite glucolimnanthin, which can be converted into pesticidal compounds such as 3-methoxybenzyl isothiocyanate (ITC) and 3-methoxyphenylacetonitrile (nitrile) in the presence of the enzyme myrosinase from unprocessed, ground meadowfoam seed. In previous studies, we demonstrated that ITC and nitrile derived from meadowfoam seed meal are toxic to the plant-parasitic nematode Meloidogyne hapla and the plant pathogen Pythium irregulare. In this study, we evaluated factors that influence the implementation of meadowfoam seed meal into agricultural production systems for soilborne pathogen control. Rate-finding experiments demonstrated that a 1.0% seed/seed meal formulation (w/w) was necessary to achieve nematode and pathogen suppression; seed meal alone was insufficient for complete M. hapla control and it stimulated the growth of P. irregulare. When 1.0% seed/seed meal formulation was used, a greater soil amendment rate was required to cause 100% mortality in P. irregulare (1.0% w/w) than for M. hapla (0.5% w/w). In phytotoxicity experiments, soils amended with the 1.0% seed/seed meal formulation were toxic to wheat, cucumber, and tomato. However, phytotoxic effects could be mitigated by delayed planting into seed meal/seed amended soils. A final assay to monitor the release of ITC and nitrile as a function of M. hapla and P. irregulare mortality was conducted over a 6 day period in soils amended at 0.5 and 1.0% with the 1.0% seed/seed meal formulation. The response was rapid, with 100% mortality of both organisms within 2 h after exposure to amended soil. Concentrations of nitrile remained relatively constant over the 6 day period (~0.017 and 0.032 mg/ml at 0.5 and 1.0% amendment rates, respectively), whereas ITC production increased rapidly and peaked 12 to 24 hrs after amendment (0.083 and 0.171 mg/ml at 0.5 and 1.0% amendment rates, respectively) before returning to near undetectable levels.