Plant Science 211 (2013) 1–7 Contents lists available at SciVerse ScienceDirect Plant Science jo ur nal home p age: www.elsevier.com/locate/plantsci QTL validation and stability for volatile organic compounds (VOCs) in apple Fabrizio Costa a,∗ , Luca Cappellin a , Elena Zini a , Andrea Patocchi b , Markus Kellerhals b , Matteo Komjanc a , Cesare Gessler c , Franco Biasioli a a Research and Innovation Centre, Foundation Edmund Mach, Via Mach 1, 38010 San Michele all’Adige (TN), Italy b Research Station Agroscope Changins-Wädenswil, Plant Protection and Fruit and Vegetable Extension Division, Schloss 1, CH-8820 Wädenswil, Switzerland c Swiss Federal Institute of Technology, ETH Zürich, Plant Pathology Group, IBZ, Universitätstrasse 2, CH-8092 Zürich, Switzerland a r t i c l e i n f o Article history: Received 22 April 2013 Received in revised form 28 May 2013 Accepted 31 May 2013 Available online 7 June 2013 Keywords: VOCs QTL mapping Apple fruit quality Aroma production QTL stability a b s t r a c t The aroma trait in apple is a key factor for fruit quality strongly affecting the consumer appreciation, and its detection and analysis is often an extremely laborious and time consuming procedure. Molecular markers associated to this trait can to date represent a valuable selection tool to overcome these limita- tions. QTL mapping is the first step in the process of targeting valuable molecular markers to be employed in marker-assisted breeding programmes (MAB). However, a validation step is usually required before a newly identified molecular marker can be implemented in marker-assisted selection. In this work the position of a set of QTLs associated to volatile organic compounds (VOCs) was confirmed and validated in three different environments in Switzerland, namely Wädenswil, Conthey and Cadenazzo, where the progeny ‘Fiesta × Discovery’ was replicated. For both QTL identification and validation, the phenotypic data were represented by VOCs produced by mature apple fruit and assessed with a Proton Transfer Reaction-Mass Spectrometer (PTR-MS) instrument. The QTL-VOC combined analysis performed among these three locations validated the presence of important QTLs in three specific genomic regions, two located in the linkage group 2 and one in linkage group 15, respectively, for compounds related to esters (m/z 43, 61 and 131) and to the hormone ethylene (m/z 28). The QTL set presented here confirmed that in apple some compounds are highly genetically regulated and stable across environments. © 2013 Elsevier Ireland Ltd. All rights reserved. 1. Introduction In the modern definition of fruit quality, aroma is considered one of the main factors together with appearance, texture and nutri- tional properties [1]. The importance of aroma is due to its direct influence on the consumer appreciation, since a pleasant aromatic “bouquet” is a fundamental requirement for a high fruit quality standard. In apple, as well as in other fruits, the aroma composi- tion/intensity changes dramatically during the fruit development as well as throughout maturation and ripening [2–5]. In this lat- ter phase of the fruit ontogenic cycle, and especially during the postharvest ripening, the impact of the apple aroma acquires a fun- damental importance. During this stage, in fact, the blend of aroma is positively regulated by ethylene, a gaseous hormone triggering the late ripening climacteric dependent physiologic responses [6]. ∗ Corresponding author at: Research and Innovation Centre, Foundation Edmund Mach, Via Mach 1, 38010 San Michele all’Adige, Trento, Italy. Tel.: +39 0461 615358; fax: +39 0461 650956. E-mail address: fabrizio.costa@fmach.it (F. Costa). Besides this, the volatile organic compounds (VOCs) forming aroma play other important biological functions, acting as signalling molecules for the host–insect interaction [7,8]. The VOC set in apple is biochemically composed by major classes of compounds, such as alcohols, aldehydes, ketons, polypropanoids, sesquiterpens and esters, which are produced by four main biochemical pathways: fatty acid, isoleucine, -farnesene and the phenylpropanoid [6,9]. The latter category (esters) is the most important class for apple, representing the major volatile compound (∼90%) produced dur- ing the apple fruit ripening process [10–12]. The great impact that the aroma has on the apple fruit marketability stimulated in the last decade the scientific community to gain knowledge about this physiology. Initially, extensive transcriptomic approaches, employ- ing EST expression studies, have unravelled the gene set putatively involved in the generation of flavour and aroma compounds in apple [13,14]. The specific regulation of a particular gene set during the climacteric phase of the fruit ripening, elucidating the relation- ship with the hormone ethylene, was also confirmed by the use of an apple transgenic line characterized by the functional repression of Md-ACO1 [6]. Md-ACO1 is a gene devoted to the final forma- tion of the hormone ethylene from its intermediate compound 0168-9452/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.plantsci.2013.05.018