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11 July 2018 Host Cues Mediate Growth and Establishment of Oak Mistletoe (Phoradendron leucarpum, Viscaceae), an Aerial Parasitic Plant
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The oak mistletoe (Phoradendron leucarpum, Viscaceae) is well-documented to exhibit preference for a few potential host species in a given locality, even when many potential host species are present. In trying to explain this distribution, we examined the mechanisms by which mistletoe seedlings recognize potentially suitable hosts in the Piney Woods ecoregion of east Texas. An initial survey of patterns of infection on the campus of Sam Houston State University revealed that water oak (Quercus nigra) was host to nearly half of the mistletoes observed, despite comprising less than 15% of trees surveyed. Field experiments demonstrated that light, host physiochemistry, and volatiles released from potential host trees serve as cues affecting the viability and establishment of mistletoe seedlings. These results provoked further study in controlled laboratory settings, in which it was demonstrated that chemical compounds in the bark of local host trees (compared to trees that serve as hosts elsewhere, but not in our survey) induce significantly although slightly greater seedling viability. Establishment of haustoria depended only on the presence of these chemicals, regardless of host species. Importantly, we demonstrated that three common monoterpenes, limonene, β-myrcene, and β-phellandrene induce a positive growth response of mistletoe radicles. These results taken together suggest a model to explain local host preference in P. leucarpum, in which covariation between mistletoe fruit maturity and monoterpene production by hosts determines the distribution of successful haustorial establishment.

Copyright 2018 Southern Appalachian Botanical Society
Christopher P. Randle, Brandi C. Cannon, Amber L. Faust, Angela K. Hawkins, Sara E. Cabrera, Stephen Lee, Michelle L. Lewis, Amy A. Perez, James Sopas, Timothy J. Verastegui, and Justin K. Williams "Host Cues Mediate Growth and Establishment of Oak Mistletoe (Phoradendron leucarpum, Viscaceae), an Aerial Parasitic Plant," Castanea 83(2), 249-262, (11 July 2018).
Received: 19 December 2017; Accepted: 6 June 2018; Published: 11 July 2018

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