Changes in quality-related traits and ethylene metabolism of two distinct apple genotypes grown at high vs low altitudes

Orchard locations with differing altitudinal characteristics were studied to better understand how different environmental conditions may affect the ripening process of ‘Golden Reinders’ and ‘Mandy’ apple cultivars, as well as their quality traits at harvest and after storage. During the first season, differences on quality traits at harvest and postharvest were detected between apples grown at several low and high-altitude orchards, particularly for the ‘Mandy’ cultivar. In the second season, the study focused on selected low and high-altitude orchards for both genotypes investigating the influence of the environmental conditions on ethylene metabolism and fruit quality at harvest and postharvest. Results showed that fruit grown at cooler locations exhibited increased physiological maturity at harvest. This increase in maturity was determined at an early stage, during growth, and generally associated with significant changes in the regulation of ethylene biosynthesis and signalling. Nonetheless, and despite the increased maturity, fruit from high altitude orchards, exhibited better quality after storage and during shelf-life, with improved colouration, maintained firmness and acidity, and better sensorial acceptance. These results suggest that the final quality of the apples is influenced not only by ethylene-dependent processes but also by other factors modulated by environmental cues. In fact, the impact of the environment was greater on the ‘Mandy’ cultivar, while the effect of the genotype was different between low-altitude and high-altitude locations, thus highlighting the importance of genotype ×  environment interactions for selecting genotypes with stable performance across different environments and resulting specifically interesting in the new challenging context of climate change.