Scientia Horticulturae 202 (2016) 91–98 Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Biosynthesis of fatty acids-derived volatiles in ‘Hass’ avocado is modulated by ethylene and storage conditions during ripening Miguel García-Rojas a , Alejandra Morgan b , Orianne Gudenschwager a , Sofía Zamudio a , Reinaldo Campos-Vargas b , Mauricio González-Agüero a , Bruno G. Defilippi a,∗ a Instituto de Investigaciones Agropecuarias, INIA-La Platina, Santa Rosa 11610, Santiago, Chile b Universidad Andres Bello, Centro de Biotecnología Vegetal, Facultad de Ciencia Biológicas, República 217, Santiago, Chile a r t i c l e i n f o Article history: Received 30 September 2015 Received in revised form 11 February 2016 Accepted 15 February 2016 Keywords: Persea americana Aroma Cold storage Volatile Fatty acids and ethylene a b s t r a c t The aroma in avocados (Persea americana Mill. cv. ‘Hass’) is mainly defined by fatty acids-derived volatile compounds that change according to the fruit maturity stage which is modulated by ethylene. In order to understand the changes in fatty acid substrates and gene expression involved in the synthesis of the key aroma-volatile compounds in avocado after harvest, we performed two trials using avocados harvested with 11% oil content. In the first trial avocados were ripened immediately after harvest at 20 ◦ C until reach- ing the ready-to-eat stage, and in the second trial, fruit were stored at 5 ◦ C for 30 days and then ripened at 20 ◦ C. In addition, to assess the ethylene effect in the volatile compounds and transcript levels measured, a 100 l L −1 ethylene application was carried out, at harvest or after storage for trial 1 and 2, respectively. The concentration of the key volatile compounds and fatty acids were performed by gas chromatography, and the changes in the expression of genes related to lipoxygenase derived compounds were measured by q-PCR. The results obtained indicated that ethylene modulated the production of linolenic acid and hexanal, whereas at the gene expression level, only PamLOX transcript changes responded to ethylene application, although its changes were maturity/ripening dependent. The cold storage did not generate significant changes in fatty acids and gene expression levels, but a decreased in the concentration of hexanal during the ripening was observed. © 2016 Elsevier B.V. All rights reserved. 1. Introduction The ripening of climacteric fruit, such as avocado, involves a series of coordinated metabolic events that affect the morphology, biochemistry, physiology and gene expression (Giovannoni, 2001), and these alterations modify many quality attributes, such as the color, texture and flavor of the fruit (Cai et al., 2006). The hormone that modulates a wide range of responses during fruit ripening and senescence in climacteric fruit is ethylene (Khan, 2006). In avocado, the “peak” in the production of ethylene during ripening has been specifically associated with an increase in the res- piratory rate, softening of the flesh, color change and development of aroma compounds (Kassim et al., 2013; Zamorano et al., 1994). In many fruits, the use of ethylene inhibitors has demonstrated that volatile compounds are affected differently. For example, in avo- cado, Pereira et al. (2013) demonstrated that the ethylene inhibitor 1-MCP delayed ripening and mainly affected the flavor of the fruit ∗ Corresponding author. Fax: +56 22 7575104. E-mail addresses: bdefilip@inia.cl, bdefilippi@gmail.com (B.G. Defilippi). in the middle stage of ripening. Cold storage is the most effective tool to reduce the rate of respiration and ethylene production in fruit, thus reducing the rates of metabolic processes and extending the postharvest life of the fruit (Kassim et al., 2013). Aroma-volatile compounds have a well-established role in determining the characteristic flavor of a wide variety of fruits, including apple (Malus domestica), melon (Cucumis melo), banana (Musa sp.), mango (Mangifera indica), papaya (Carica papaya L.) and tomato (Lycopersicon esculentum Mill) (Defilippi et al., 2009; Lewinsohn et al., 2001). Studies of strawberry (Fragaria x ananassa) fruit have demonstrated that the storage temperature significantly affects aroma compounds (Ayala-Zavala et al., 2004). There are also studies in climacteric fruits showing that during ripening the production of aroma volatiles are mainly derived from fatty acids modulated by ethylene (Defilippi et al., 2009; Yahia, 1994). These free fatty acids, or those liberated by lipase activity and further metabolized by -oxidative enzymes and/or lipoxygenase (LOX), are generally regarded as being the main precursors of esters, alcohols and aldehydes (Fellman et al., 2000). These compounds change as the fruit develops; for example, short-chain aldehy- des are predominant in immature avocados, particularly hexanal http://dx.doi.org/10.1016/j.scienta.2016.02.024 0304-4238/© 2016 Elsevier B.V. All rights reserved.