Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2009
Publication Date: 7/3/2009
Citation: Bacetty, A.A., Snook, M.E., Glenn, A.E., Noe, J.P., Nagabhyru, P., Bacon, C.W. 2009. Chemotaxis disruption in Pratylenchus scribneri by tall fescue root extracts and alkaloids. Journal of Chemical Ecology. 35:844-850
Interpretive Summary: The grass tall fescue is infected with a fungus that provides the necessary defenses against predatory organisms such as nematodes. The fungus resides within the grass as an endophyte. Nematodes are soil organisms that utilize specific chemoreceptor to detect and attach plant host and can destroy this grass if it is not infected with the endophyte. The mechanism for this is unknown. We modified an in vitro system that allows us to determine if specific compounds produced by the fungus modified the movement behavior (chemoreception) in a particular species of nematode, Pratylenchus scribneri, which is very parasitic on this grass. The results indicated that specific alkaloids produced by the fungal endophyte were either attractants or repellents to this nematode, which resulted in death of this pest. Extracts from the grass infected with the fungus was a repellent, while extracts made from noninfected grasses were attractants. Therefore, the alkaloids provide further evidence that ergot alkaloids and other fungal metabolites, which may not be toxic at low concentrations, nevertheless do indeed modify the chemoreception of this species of nematode preventing this species from attacking the roots of this valuable forage and conservation grass.
Technical Abstract: Tall fescue (Festuca arundinacea) forms a symbiotic relationship with the clavicipitalean fungal endophyte Neotyphodium coenophialum. Endophyte-infected grass is tolerant to nematode, but the factors responsible are unknown. The objectives of this work were to identify effects from ergot and loline alkaloids and root extracts on the chemoreception of Pratylenchus scribneri using an in vitro chemoreception bioassay. The results established that alkaloid were either strong repellents or strong attractants. Ergovaline, the major ergot alkaloid produced by the endophyte, was an attractant and caused complete death of the nematodes. Root extracts of endophyte-infected grasses cultured 45 days and older were attractants.