Reflective Film Mulching Before Harvest Promotes Coloration and Expression of Ripening-Related Genes in Peach Fruits

Fruit appearance is the most important factor of fruit quality in peach (Prunus persica). In order to determine the promotional effects of increased light in the canopy on peach fruit coloration, reflective film was applied under trees in the field 7 days before the harvest of ‘Taiko’ peach. We then investigated pigmentation of the peel, fruit traits like total soluble solids, titratable acidity, and hardness; the expression of genes related to fruit coloration and ripening in a peach fruits; and photosynthetically active radiation (PAR) inside the tree canopy treated with reflective film mulching. The color of fruit skins treated with reflective film mulching was improved significantly according to their Hunter value compared to untreated fruit. There was no significant change in total soluble solids, acid content, and hardness in fruits treated with reflective film mulching compared to control. Quantitative real-time PCR analysis revealed that transcript levels of anthocyanin biosynthetic related genes (F3H and CHS) were up-regulated; however, the expression of ethylene synthesis-related genes (ACO and ERS1) and ripening-related genes (PL and PME) was not enhanced by reflective film mulching. These results suggest that reflective film mulching improved light irradiance in the tree canopy, which promoted fruit skin coloration via the the induction of anthocyanin biosynthesis in the peel of peach. Additional key words: coloration, gene expression, peach, photosynthetically active radiation (PAR), quantitative real-time PCR, reflective film