Location: Nematology Laboratory
Title: Nematotoxicity of drupacine and a Cephalotaxus alkaloid preparation against the plant-parasitic nematodes Meloidogyne incognita and Bursaphelenchus xylophilus Authors
Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2013
Publication Date: July 30, 2013
Citation: Wen, Y., Meyer, S.L.F, Masler, E.P., Zhang, F., Liao, J., Wei, X., Chitwood, D.J. 2013. Nematotoxicity of drupacine and a Cephalotaxus alkaloid preparation against the plant-parasitic nematodes Meloidogyne incognita and Bursaphelenchus xylophilus. Pest Management Science. 69(9):1026-1033. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack crop plants and result in an annual U.S crop loss of ten billion dollars. One approach for solving the problem of the lack of safe and effective control methods for reducing these crop losses is to develop the use of naturally occurring compounds in plants for this purpose. Previous research has indicated that twigs and leaves of the Chinese plum yew are toxic toward nematodes. In this paper, a team of ARS and Chinese scientists examined these nematode-toxic effects in several nematode species and identified the chemical compound responsible for this activity. A preparation of compounds known as alkaloids was discovered to inhibit nematode hatching and movement and to reduce reproduction of plant-parasitic nematodes in a greenhouse experiment. The alkaloid with the greatest activity against nematodes was identified as drupacine. The results are significant because they represent the first report of this group of alkaloids as being toxic to nematodes. Consequently, they will be used by researchers developing the use of safe, naturally occurring chemicals for use in reducing crop losses caused by nematodes.
Technical Abstract: Species of Cephalotaxus (the plum yews) produce nematotoxic compounds of unknown identity. Consequently, bioassay-guided fractionation was employed to identify the compound(s) in Cephalotaxus fortunei twigs and leaves with activity against plant-parasitic nematodes. A crude alkaloid extract, particularly drupacine, was responsible for much of the nematotoxicity. The LC50 of drupacine for Bursaphelenchus xylophilus was 27.1 ug/ml, and for Meloidogyne incognita it was 76.3 ug/ml. Immersion of M. incognita eggs in 1.0 mg/ml crude alkaloid extract (the highest tested concentration) reduced hatch 36%; immersion of second-stage juveniles resulted in 72% to 98% immobility. Crude alkaloid extract and drupacine suppressed protease activity in extracts of the microbivorous nematode Panagrellus redivivus 50% and 80%, respectively. Application of 0.02 to 0.5 mg/ml crude alkaloid extract to soil with M. incognita inoculum did not significantly reduce pepper plant shoot length or weight, compared with nematode-inoculated, water-treated controls, but the number of eggs per root system decreased by 83% at 0.05 mg/ml. Drupacine and a crude alkaloid extract suppress nematode hatch, activity of mixed life stages, and population numbers on plant roots. This is the first demonstration of nematotoxicity of crude Cephalotaxus alkaloids and drupacine.