Potential Role of Alkaloids and Monoamines in Ash Resistance to Emerald Ash Borer

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Previous work to dissect mechanisms of resistance of ash to emerald ash borer (EAB), an alien invasive wood-boring beetle that threatens to extirpate North American green, white, and black ash, has implicated a role for constitutive and induced phloem proteins and phenolics. However, nothing is known about the potential role of alkaloids or non-amino acid amines. In particular, resistant Manchurian ash contains 9 to142 times more tyramine (a known neurotransmitter) than susceptible North American ash. Furthermore, EAB genes potentially involved in neurotransmitter detoxifi cation were up-regulated in the midgut of larvae feeding on Manchurian ash phloem. Recently, we have shown that low water availability increases ash susceptibility, but does not affect induced phloem phenolics. The aim of this study was to determine if alkaloids and tyramine contribute to the differential resistance of Manchurian and black ash to EAB attack, and if their concentration is infl uenced by water availability. HPLC-PDAMS and GC-MS were employed to characterize phloem chemical composition, while artifi cial diet bioassays were used to test effects of candidate resistance compounds, including tyramine, on growth and survival of EAB larvae.


Presented at the XXIV IUFRO World Congress, Salt Lake City, UT.