|Mitchell, Ashaki - Teddi|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2013
Publication Date: 3/25/2013
Publication URL: http://handle.nal.usda.gov/10113/58054
Citation: Meyer, S.L.F., Nyczepir, A.P., Rupprecht, S.M., Mitchell, A.D., Martin, P.A., Brush, C.W., Chitwood, D.J., Vinyard, B.T. 2013. Tall fescue ‘Jesup (Max-Q)’: Meloidogyne incognita development in roots and nematotoxicity. Agronomy Journal. 105(3):755-763. Interpretive Summary: Root-knot nematodes are a major pest of young peach trees because these microscopic worms damage roots and cause stunted growth of above-ground plant parts, early defoliation, reduced tree vigor, and occasionally tree death. In order to manage nematodes on peach trees, tall fescue cultivar Jesup (Max-Q) was recently recommended as a cover crop to be planted prior to establishment of peach orchards. This tall fescue cultivar is associated with a fungus that is beneficial to growth of the plant, but unlike some of the fungi that live inside tall fescue, does not produce toxins that cause disease in grazing animals. In order to improve nematode management, studies were done to examine how Jesup (Max Q) reduces nematode populations. In the laboratory, compounds from roots and shoots of tall fescue cv. Jesup (Max-Q) reduced root-knot nematode egg hatch, and compounds extracted from roots killed root-knot nematodes. Greenhouse studies demonstrated that few root-knot nematodes infected and developed in tall fescue Jesup (Max Q) roots. The results are significant because they indicate that compounds derived from Jesup (Max-Q) tall fescue can decrease numbers of live nematodes, but chemicals in the plant are likely only one of the factors involved in suppressing root-knot populations in the roots and soil. This research will be used by scientists and growers who are developing use of Jesup (Max Q) for decreasing economic losses due to nematodes in peach orchards.
Technical Abstract: Tall fescue cv. Jesup (Max-Q) was recently recommended as a preplant ground cover for managing plant-parasitic nematodes on peach trees in the southeastern United States. Jesup (Max-Q) is associated with a strain of the endosymbiotic fungus Neotyphodium coenophialum that does not produce ergot alkaloids that cause fescue toxicosis. To optimize use of this tall fescue for lowering populations of the root-knot nematode Meloidogyne incognita, greenhouse and laboratory studies were conducted on selected factors potentially contributing to suppression. Tall fescue-derived extracts and exudates were tested for nematotoxicity, and M. incognita life cycle development was compared between susceptible tomato and Jesup (Max-Q) roots. The highest tested concentrations of root and shoot extracts inhibited M. incognita hatch up to 46% compared with controls, and were nematotoxic to the infective second-stage juveniles (J2; up to 66% decrease in viability). Root exudates were also nematotoxic to J2 (up to 27% mortality), and inhibited hatch up to 48%. Roots of susceptible tomato plants (controls) had ca. 3 to 7 times more infective J2 than tall fescue roots, 40 to 80 times more females and egg masses, > 1800 times more eggs/plant, and 10 to 83 times more galls/plant. The nature of Jesup (Max-Q) suppression of M. incognita included low J2 penetration rate and failure of infective J2 to complete their life cycle in this cultivar. In addition, compounds derived from Jesup (Max-Q) tall fescue decreased nematode viability, also contributing to the suppression of M. incognita by this plant.