Arbutin is a hydroquinone derivative that has been found in species of several plant families. Within the genus Origanum the formation of arbutin is polymorphic, with arbutin present in considerable amounts (O. dubium 20.8 +/- 15.3 mg/g; wild O. majorana 51.3 +/- 15.4 mg/g, cultivated O. majorana 40.6 +/- 11.2 mg/g), minor amounts (O. microphyllurn 0.1 +/- 0.1 mg/g, wild O. onites 0.3 +/- 0.1 mg/g, cultivated O. onites 0.1 +/- 0.1 mg/g, O. saccatum 0.1 +/- 0.1 mg/g, O. solymicum 0.4 +/- 1.0 mg/g) or completely absent (O. husnucan-baseri, O. syriacum, O. vulgare). Whereas the most important commercial oregano species (O. onites and O. vulgare) contain no or only minor amounts of arbutin, marjoram (O. majorana) has considerably high amounts. The high variability of arbutin in O. majorana would allow a selection into cultivars with high arbutin content and low arbutin varieties. In a segregating F-2-generation of a species crossing between O. majorana (high content of arbutin) and O. vulgare ssp. vulgare (free of arbutin), the presence of arbutin followed a Mendelian segregation of 3:1, indicating that only one gene is responsible for the polymorphism of arbutin in the genus Origanum. The absence of arbutin in O. vulgare ssp. vulgare or O. syriacum would even enable the breeding of marjoram with no arbutin at all. (C) 2009 Elsevier Ltd. All rights reserved.