Abstract

Pear fruit (Pyrus communis L.) is an economically important fruit crop grown in Chile. In order to reach world markets, mid and long-term storage is required. During this period, several physiological disorders causing peel and flesh symptoms are developed as a result of chilling injury, affecting fruit quality and marketability. Among them, superficial scald is the most important in susceptible cultivars, not only in Chile but also worldwide (Chen et al., 1990; Whitaker et al., 2009; Lurie and Watkins, 2012). In D’Anjou pears SS incidence can reach 100% after only 3 months of cold storage. In Packham’s Triumph, incidence can vary between 10-50% after 4 months of cold storage and 100% after 6 months. Superficial scald (SS) is a common physiological disorder in apples and pears that develops after low temperature storage. Sympoms appear as irregular and rough brown-black patches only in the peel after fruit has returned to room temperature (20ºC), a common charcateristic of chilling stress-related physiological disorders. Although superficial scald on apples has been studied for more than 100 years, there are still some unknowns regarding metabolic and molecular mechanisms involved in its development. In pears, although it is also a pome fruit, this knowledge is scarcer, especially regarding biochemical and molecular bases, and how pre-and postharvest predisposing factores affect SS expression. Among predisposing factors, genotype, temperature pre-harvest and fruit maturity at harvest have been shown to have an important role on SS development. Postharvest, storage length and temperature, and treatment are key on SS expression (Lurie & Watkins, 2012; Isidoro & Almeida, 2006, 2008; Zoffoli et al., 1998). All of them have specific effects on biochemical and molecular mechanisms involved in the disorder development, such as a-farnesene levels, enzymes and genes involved in its biosynthesis, its oxidation products (trienols, among others), and antioxidants mechanisms. Most of this information is only available in apples. Therefore, due to the lack of metabolic and genetic information on superficial scald development on pears, as well as comprehensive studies involving metabolomics and transcriptomics techniques, there is an opportunity to have an important scientific impact with the proposed study. The general goal of the study is to determine metabolic and transcripts profiles during scald development in pears, in order to identify potential biomarkers to use as a predictive tool prior or during long-term storage. The specific goals are: -To correlate metabolic profiling and gene expression in fruit during different growing conditions conducive to superficial scald development in pears, -To correlate metabolic profiling and gene expression in fruit with different postharvest treatments and storage conditions, and -To generate a predictive model combining different biomarkers that would work under different growing conditions and postharvest managements. Pre-and Postharvest experiments will be carried out in commercial orchards and storage and laboratory facilities at the Centro de Pomaceas Research Center. Metabolomic work will be carried out using UHPL-ms and GC-ms methods at the same Center. Transcriptomics and molecular work will be carried out at the Posthavest Unit, Inia La Platina.