Candidate genes transcriptional study in ‘Granny Smith’ apples in response to prolonged storage at different conservation strategies

Apple (Malus domestica) is one of the most cultivated fruit crop word wide (86.442.716 tons, FAOSTAT 2020) characterized by a mid-late summer harvesting. To satisfy the continue demand of fresh product ensuring a constant availability of this produce to the market, fruit must be stored for prolonged period. Nowadays this is facilitated by the employment of modern storage technologies based on low temperatures (1-4°C), slowing down the entire metabolisms, and the inhibition of the ripening process. The control of the ripening syndrome can be achieved through a controlled atmosphere characterized by a low-oxygen and high CO2 content, inhibiting the biosynthesis of the hormone ethylene, and/or treatment with the ethylene competitor 1-MCP that acting at the perception level efficiently block the signal transduction pathway. With the aims to improve and optimized the storage strategy reducing the quality loss and avoiding and/or limiting the onset of related physiopathology or post-harvest disorder, a deeply understanding of how these conditions affect the ripening process and the quality of apples becomes essential. In this study, different batches of ‘Granny Smith’ apple fruit were stored in various storage conditions, such as: Dynamic-Controlled-Atmosphere (DCA), static Ultra-Low-Oxygen mode (ULO) and classical Regular-Atmosphere, with and without application of 1-MCP treatment. After six months of storage, apples were transferred at room temperature for 12 hours or 7 days simulating a commercial shelf-life. The postharvest ripening physiology was assessed by analyzing the transcriptional pattern of candidate genes involved in ethylene biosynthesis and ripening (ACO1, ACS1 and PG1), signal transduction pathway in response to low-oxygen (ERF-VIIs), sugars and anaerobic metabolisms (amylase, glucose-6-P-isomerase, pyruvate dehydrogenase and alcohol dehydrogenase). The transcriptional profiles of these elements provided important results about the physiological behavior of the fruit stored at different atmospheric conditions.