Host Preferences of Beechdrops (Epifagus): Evidence from Chloroplast DNA Sequence Data

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In nearly two hundred years, botanists and the general public have assumed that Epifagus virginiana (beechdrops) parasitizes specifically on the roots of Fagus grandifolia(American beech tree). In this study we used sequences of the chloroplast gene rbcL from host roots of beechdrops to test the long-held theory. Host roots on which Epifagus grows were randomly collected from four localities in Western Michigan. Our data show that although roots of maple and beech are intricately interwoven with the grappler roots of Epifagus, all of our root samples for which we verified the host-parasite direct connections dissecting microscope were from American beech trees (Fagus grandifolia) except for one from Acer saccharum. The potential beechdrop-sugar maple relationship needs further verification from physiological investigations. Therefore, out DNA sequence data support the host preference of Epifagus on roots of Fagus and suggest that parasite-root interactions may be complex and DNA barcoding can be useful for studying the host preference of parasitic plants.