Postharvest Biology and Technology 99 (2015) 120–130 Contents lists available at ScienceDirect Postharvest Biology and Technology journal h om epa ge : www.elsevier.com/locate/postharvbio The detection of fungal diseases in the ‘Golden Smoothee’ apple and ‘Blanquilla’ pear based on the volatile profile Luisa López a,b,∗ , Gemma Echeverria a , Josep Usall a , Neus Teixidó a a IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic de Gardeny, Fruitcentre Building, 25003 Lleida, Spain b University of Lleida, XaRTA-Postharvest, Av. Alcalde Rovira Roure, 191, 25198 Lleida, Spain a r t i c l e i n f o Article history: Received 22 May 2014 Accepted 8 August 2014 Keywords: ‘Golden Smoothee’ apple ‘Blanquilla’ pear Volatile compounds Penicillium expansum Rhizopus stolonifer a b s t r a c t Blue mould caused by Penicillium expansum is one of the major pathogens causing serious losses during the postharvest and storage periods of apples and pears. Rhizopus stolonifer has also been identified as the causative agent of important rot losses in these fruit in packinghouses after humid spring seasons. An early disease detection system could help to reduce such losses. Biotic interactions affect the emission of volatile compounds during infection, and this changed the volatile profile of ‘Golden Smoothee’ apples and ‘Blanquilla’ pears inoculated with P. expansum and R. stolonifer throughout their shelf-life at 20 ◦ C for up to 7 days. Dynamic headspace-gas chromatography was used to determine if infected fruit emitted distinct volatile compounds different from those of non-infected fruit and if volatile emissions could be detected before the infection was visible in the fruit. According to the results obtained in ‘Golden Smoothee’ apples inoculated with both pathogens, Z-3-hexenyl 2-methylbutanoate could be a potential biomarker because it was quantified before these diseases were visible and was not detected in non- inoculated control fruit. Similar results were obtained for 2-butanone and -pinene in ‘Blanquilla’ pears inoculated with R. stolonifer. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Blue mould caused by Penicillium expansum Link is the most important postharvest disease of apples and pears. Rhizopus stolonifer (Ehrenb. Ex Fr.) Lind causes Rhizopus rot in pome fruit. However, while Rhizopus rot is a serious disease of stone fruit, it has not been considered to be a major pome fruit disease because the development of this species is inhibited at temperatures below 5 ◦ C. Therefore, the rot is prevented at the storage temperatures recommended for storing apples and pears (Barkai-Golan, 2001). However, Rhizopus rot causes important rot losses in Spanish pack- inghouses in stored apples, and especially in pears after humid spring seasons. R. stolonifer strains isolated from decayed fruit at cold storage conditions could cause disease in pears and apples artificially inoculated and stored at −1 ◦ C and 0 ◦ C, respectively, in our laboratory (Usall et al., 2013). Methods for controlling postharvest fungal diseases of fresh fruit vary and depend on the requirements of the target markets. ∗ Corresponding author at: IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic de Gardeny, Fruitcentre Building, 25003 Lleida, Spain. Tel.: +34 973032850x1597; fax: +34 973238301. E-mail address: mluisa@tecal.udl.cat (L. López). Chemical fungicide treatments are the main means to control these diseases. The application of fungicide mixtures has proven effective for controlling rot in apples (Barkai-Golan, 2001) and pears (López and Riba, 1999), but fungicide residues remain in the fruit as a con- sequence of postharvest treatment (Villatoro et al., 2009a,b) and are not desired by consumers in some markets. Various alterna- tive methods have been tested to replace chemicals, such as heat treatments (Dang et al., 2008), biocontrol (Teixidó et al., 2011), modifying the storage atmosphere (Akbudak et al., 2009) and low- toxicity treatments, such as peracetic acid (Alvaro et al., 2009). However, these methods are limited and raise concerns. The detection of diseases in stored apples and pears is very difficult, especially in controlled atmosphere conditions, in which storage chambers are closed for long periods of time and dis- ease development in the fruit cannot be visually detected. When these diseases can finally be observed, they are in a very advanced stage and interventions to reduce losses are not possible. Rot- ten fruit usually produce a characteristic odour that sometimes differs depending on the pathogen causal agent (Wihlborg et al., 2008) and the fruit. Several studies have been performed to evaluate the changes in the volatile emissions caused by fun- gal infection in apples (Vikram et al., 2004a,b; Karlshøj et al., 2007). Vikram et al. (2004a,b) reported that compounds such as dimethyl ether and propanal were specific to ‘Cortland’ apples http://dx.doi.org/10.1016/j.postharvbio.2014.08.005 0925-5214/© 2014 Elsevier B.V. All rights reserved.