Identification of potential molecular markers for detection of lengthy chilled storage of L. fruit.

Low temperature is the main strategy to preserve fruit quality post-harvest, in the supply chain. Low temperatures reduce the respiration, ethylene emission, and enzymatic activities associated with senescence. Unfortunately, peaches are sensitive to low temperatures if exposed for long periods, resulting in physiological disorders that can compromise commercial quality. Maximum damage occurs at 5 °C while at 1 °C damage is reduced. Therefore, rapid early detection methods for the distribution chain to monitor length and temperature of fruit storage are needed. The aim of this work was to identify candidate genes to develop an antibody-based marker system in peach fruit to monitor chilled storage. Two cultivars were tested: 'Sagittaria', an early ripening peach, and 'Big Top' a mid-season ripening nectarine, with delayed softening and resistance to supply-chain conditions. Both cultivars were subjected to 1 or 5 °C chilled storage for different times to simulate typical supply-chain conditions. Identification and expression of potential marker genes was assessed using a previous transcriptomic study following storage at 1 °C. Fifteen candidate genes were selected, however only seven proteins encoded were suitable as protein markers as they lack a transmembrane domain. Real-time qPCR using fruit from the subsequent year to the transcriptome was used to assess expression at both 1 and 5 °C chilled storage of five candidate genes. Four genes and the related proteins were identified that would be suitable for the development of molecular markers: a Pathogenesis-Related Bet v I family protein, a dehydrin, a Glycosyl hydrase family 18 protein and a Late Embryogenesis abundant protein.