Biosynthesis of fatty acids-derived volatiles in 'Hass' avocado is modulated by ethylene and storage conditions during ripening

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 degrees C until reaching the ready-to-eat stage, and in the second trial, fruit were stored at 5 degrees C for 30 days and then ripened at 20 degrees C. In addition, to assess the ethylene effect in the volatile compounds and transcript levels measured, a 100 mu 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. (C) 2016 Elsevier B.V. All rights reserved.