Biochemical and genetic implications of the slow ripening phenotype in peach fruit

The peach [Prunus persica L. (Batsch)] slow ripening (SR) trait is a mutation preventing the normal fruit ripening process. It is determined by a single Mendelian gene (Sr/sr) located on linkage group 4, where only homozygous individuals for a recessive allele (sr) show the SR phenotype and are generally discarded from breeding programs. Ripening-related traits such as fruit weight, firmness loss, ethylene production, ACO activity, sugars and organic acids composition, malondialdehyde, antioxidant capacity and total phenolic content were evaluated in a segregating population for the SR trait during two consecutive harvest seasons and at different maturity stages. Although there is no commercial value for the slow ripening (srsr) individuals, our results demonstrate that a heterozygous combination involving sr and another allele at this locus (Sr2) showed interesting traits including a longer harvest window and improved postharvest behaviour if harvested at the appropriate maturity (I-AD >= 2). All these traits seem to be linked to a delayed ripening behaviour mediated, in turn, by a lower ethylene production capacity and an altered sugar (mainly sucrose) and organic acid accumulation/utilisation on-tree. The selection of this allelic combination could be an easy and efficient strategy to obtain new peach cultivars with potentially improved shelf life.