Submitted to: Journal of Nematology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/27/2006
Publication Date: 9/1/2006
Citation: Meyer, S.L., Zasada, I.A., Roberts, D.P., Vinyard, B.T., Lakshman, D.K., Lee, J., Chitwood, D.J., Carta, L.K. 2006. Plantago lanceolata and plantago rugelii extracts are toxic to meloidogyne incognita but not to certain microbes. Journal of Nematology 38(3):333-338. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause ten billion dollars in U.S. crop losses annually. Root-knot nematodes are among the most destructive species. One problem facing growers is the lack of safe and effective methods for controlling nematode-induced crop losses. Because of this need for new management agents, two commonly occurring species of plantain (Plantago) were tested for production of compounds toxic to root-knot nematode, to three beneficial biocontrol microbes, and to four fungi that cause plant disease. The study demonstrated that extracts from roots and shoots of both species were toxic to the nematode, but not to the tested bacteria and fungi. The results are significant because they demonstrate that these species of plantain are a source of nematicidal natural products. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: Extracts from the plants Plantago lanceolata and P. rugelii were evaluated for toxicity to the root-knot nematode Meloidogyne incognita, the beneficial microbes Enterobacter cloacae, Pseudomonas fluorescens and Trichoderma virens, and the plant-pathogenic fungi Fusarium oxysporum f. sp. gladioli, Phytophthora capsici, Pythium ultimum, and Rhizoctonia solani. Wild plants were collected, roots were excised from shoots, and the plant parts dried and ground to a powder. One set of extracts (10% w/v) was prepared in water and another in methanol. Treatments included extract concentrations of 25%, 50%, 75% and 100%, and water controls. Meloidogyne incognita egg hatch was recorded after 7-day exposure to the treatments, and second-stage juvenile (J2) activity after 48 hours. All extracts were toxic to eggs and J2, with P. lanceolata shoot extract tending to have the most activity against M. incognita. Numbers of active J2 remained the same or decreased in a 24-hour water rinse following the 48-hour extract treatment, indicating that the extracts were lethal. When data from water- and methanol-extracted roots and shoots of both plant species were combined for analysis, J2 tended to be more sensitive than eggs to the toxic compounds at lower concentrations, while the higher concentrations (75% and 100%) were equally toxic to both life stages. The effective concentrations causing 50% reduction (EC50) in egg hatch and in J2 viability were 44.4% and 43.7%, respectively. No extract was toxic to any of the bacteria or fungi in our assays.