|Glenn, Anthony - Tony|
Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/5/2009
Publication Date: 12/1/2009
Publication URL: hdl.handle.net/10113/38784
Citation: Bacetty, A.A., Snook, M.E., Glenn, A.E., Noe, J.P., Hill, N., Culbreath, A., Timper, P., Nagabhyru, P., Bacon, C.W. 2009. Toxicity of Endophyte-Infected Tall Fescue Alkaloids and Grass Metabolites on Pratylenchus scribneri. Phytopathology. 99(12):1336-1345. Interpretive Summary: The perennial cool season forage and turf grass tall fescue is an essential grass found throughout the southeastern and Midwestern USA, representing well over 32 million acres. This grass is naturally infected with a fungus, Neotyphodium coenophialum, a fungal endophyte. This fungus is responsible for protecting the grass from several pests and mammals. We initiated tests to determine if this fungus was responsible for resistance to the plant parasitic nematode that normally devastate this and other grasses. We use the nematode Pratylenchus scribneri, in an in vitro bioassay for testing the toxicity to several root extracts and purified compounds produced by the fungus, such as ergot alkaloids and the lolines alkaloids. The results indicate that root extracts from plants infected with the fungus was toxic to the nematode as oppose to extracts from grasses without the endophyte. The in vitro assay indicated that plant metabolites, the fungal metabolites, ergot, and loline alkaloids, are toxic to this species of nematode, and that there potentiating and synergistic effects are occurring in the plants. This provides the first evidence of toxicity from these groups of compounds to a plant parasitic species.
Technical Abstract: Tall fescue (Festuca arundinacea) is a perennial, cool-season turf and forage grass species in the United States that covers over 20 million hectares of pastureland. Neotyphodium coenophialum, an endophytic fungus associated with this cool-season grass, enhances host fitness and imparts pest resistance to the grass. Biologically active alkaloids and other secondary metabolites are produced in this association that has been implicated in the reduction of plant-parasitic nematode populations. Currently there is little information available on the effects of any biologically active compounds on nematode resistance in tall fescue. In vitro toxicological interactions of ergot and loline alkaloids, as well as polyphenolic compounds, from endophyte-infected tall fescue, cv Jesup, on toxicity to the lesion nematode, Pratylenchus scribneri were investigated. The in vitro bioassay assessed the effects of specifically identified and fractions and compounds on P. scribneri motility, and mortality. Separate greenhouse studies evaluated the effects of endophyte-infected or non infected tall fescue on P. scribneri viability. Root extracts from Jesup tall fescue were determined to be nematistatic to this nematode, which indicated that endophyte-infected roots contained substances that might be measured in the in vitro bioassay. Individual tests of several ergot alkaloids revealed that ergovaline and a-ergocryptine were nematicidal at 5µg/ml and 50µg/ml respectively. This work identified some of the biologically active compounds produced in endophyte-infected tall fescue, cv Jesup as nematotoxic and should be further studied to enumerate their modes of action against other plant-parasitic nematodes.