153 Marker-Assisted Breeding: Monoterpene Levels in Different Grapevine (Vitis vinifera L.) Cultivars/Clones and the Identification of Potential Monoterpene Synthases O. Bitz a , M. Nitsch, O. Budich, M. Schmidt, S. Rolletter, M. Hey and E. Ruehl Geisenheim University von Lade-Str. 1, 65366 Geisenheim Germany Keywords: grape, aroma, flavour, cultivars, allele, monoterpenes, terpene synthases Abstract Monoterpenes are considered to be one of the major classes of volatile flavour components in many grapevine cultivars and are characteristic of fruity and floral white wines. The purpose of this study was to compare seasonal variation in monoterpene levels of different grape cultivars and characterise metabolic pathway genes leading to monoterpene production. Grape cultivars with different aromatic attributes (high to low aroma) and non-aromatic cultivars were collected at different stages during several seasons from our experimental vineyard in Geisenheim. Monoterpenes were extracted using solid phase extraction (SPE) and analysed by GC/MS. This study focused on major monoterpene alcohols linalool, geraniol and α-terpineol. In this study putative grape monoterpene synthase genes from several cultivars were sequenced and their potential for marker-assisted breeding assessed. INTRODUCTION Terpenes are widespread in the plant kingdom, with different functions including pest protection and attraction of insects to pollinate flowers. Monoterpenes are compounds of the secondary metabolism in different plant species. They are mostly synthesized over a mevanolate-independent plastid pathway. The precursor geranyl pyrophosphate (GPP) is generated enzymatically from two isopentenyl pyrophosphate (IPP) units (Lichtenthaler, 1999) and transformed into monoterpenes by terpene synthases. In white wine, monoterpenes largely determine the characteristic aroma profile and are typical for fruity and floral white wines. Cultivar character largely depends on the type and level of monoterpenes. It was shown that twelve monoterpenes (linalool, nerol, geraniol, pyranoid linalool oxides (cis + trans), furanoid linalool oxides (cis + trans), 3,7-dimethylocta-1,5-diene-3,7-diol, hotrienol, citronellol, nerol oxide and (E)-geranoic acid) could characterise grape cultivars and group them into three aromatic classes: (1) cultivars with a high aromatic ‘Muscat’ related aroma, (2) with a fruity ‘Riesling’-related aroma and (3) cultivars with a neutral bouquet (Rapp, 1990). The biosynthesis and molecular genetics of monoterpenes have been widely studied in various species and a set of functional terpene synthases were described by Martin et al. (2010). The recently published genome of grapevine (Jaillon et al., 2007; Velasco et al., 2007) and sequences from several plant species available in databases enabled us to identify and characterise potential monoterpene synthases in grapevine. MATERIAL AND METHODS Aroma Analysis In 2009, 18 genotypes, 12 cultivars, 6 clones of ‘Riesling’ (‘White Riesling’) and 2 clones of ‘Red Traminer’ (Gewürztraminer) were sampled at different ripening stages between July 15 and October 5 at Geisenheim University. For monoterpene extraction, a oliver.bitz@hs-gm.de Proc. II nd IS on Biotechnology of Fruit Species Ed.: S.E. Gardiner Acta Hort. 1048, ISHS 2014