Candidate Gene Expression Profiling Reveals a Time Specific Activation during Fruit Development and Ripening in Apple

Fruit quality is the result of a series of genetically programmed modifications that taking place from fruit development progress until the moment of harvest. In the practical management, apples are, however, harvested at the horticultural maturity stage, for a period of time dependent to the orchard size. In this perspective, the identification of the most suitable harvest time plays a decisive role, in order to compromise the achievement to the best fruit quality features with the most favourable postharvest performance.

In this work, the general fruit ripening of two apple cultivars distinguished by a different ripening behaviour (‘Golden Delicious’ and ‘Fuji’) was assessed over a window of three weeks established around the commercial harvest. The physiological stage of the fruit collected from each harvest date was characterized by investigating the ethylene production and fruit texture, as well as the expression profile of a specific gene set. In the particular case, twelve candidates involved in three main pathways, such as ethylene, auxin and cell wall metabolism were chosen. The functional profile of this gene set revealed a specific time based activation, highlighting, moreover, their dependence with respect to the hormone ethylene. The analysis of the overall transcription pattern suggests as these elements can be proposed as a novel diagnostic toolkit to monitor and characterize the fruit quality modification around harvest. A more informed and specific characterization of the maturity progression would allow a better organization of the harvest and postharvest management, enabling the commercialization of fruit characterized by a higher quality.