Candidate gene expression profiling reveals a time specific activation among different harvesting dates in ‘Golden Delicious’ and ‘Fuji’ apple cultivars

Fruit quality is a combination of several features impacting the general consumers’ appreciation, and it is thought as the final result of a complex physiological mechanism ongoing during the entire ontogenic life cycle. In the horticultural management apples are normally stored for a long period, ensuring the availability of fresh fruit on the market over a year-round period. In this context, the role of postharvest is to preserve the properties gained at harvest without sacrificing the general fruit quality. In this scenario, the choice of the most appropriate harvest time plays a crucial role, representing a compromise between the achievement of a sufficient quality and the mechanical resistance to harvest and postharvest practice. So far the harvesting time has been defined with too elementary and empirical tools, making thus difficult the selection of a proper harvesting window. In this work, the expression profile of thirteen genes involved in auxin, ethylene as well as cell wall metabolism have been assessed over several dates of two apple cultivars distinguished by a different ripening behavior, such as ‘Golden Delicious’ and ‘Fuji’. The monitoring of the apple fruit maturity by candidate gene transcription profiling propose these elements as novel biomarkers, suggesting the first 10 days, after the commercial harvest, as the most appropriate harvesting window for ‘Golden Delicious’. In ‘Fuji’, instead, the time frame resulted more extended, due to a reduced expression of marker genes and slower ripening progression