Effect of low temperatures on pulp browning and endogenous abscisic acid and ethylene concentrations in peach (Prunus persica L.) fruit during post-harvest storage

摘要

Changes in the severity of pulp browning, endogenous abscisic acid (ABA) and ethylene concentrations, and related gene expression in peach (Prunus persica L. 'Bayuecui') fruit stored at the biological freezing-point temperature (BFT; -1 degrees C), at 4 degrees C, or at room temperature (20 degrees C; as a control) were investigated. The results showed that fruit stored at room temperature showed climacteric changes in ethylene and ABA concentrations and in levels of expression of the corresponding ethylene synthetase genes (PpACS1, PpACO1) and the gene for a key enzyme of ABA synthesis (PpNCED), concomitant with a significant decrease in fruit firmness and an increase in juice yield. Meanwhile, two sucrose synthase genes (PpSUS1 and PpSUS2) were expressed at relatively low levels. However, fruit firmness decreased slightly and chilling injury (CI) increased significantly 40 d after storage (DAS) at 4 degrees C, with a significant accumulation of proline [from 8.33 mu g g(-1) (at t = 0 d) to 9.125 mu g g(-1) (at t = 40 d)]. In contrast, fruit firmness decreased slowly and pulp browning increased slightly 80 DAS at the BFT (-1 degrees C), with a lower accumulation of proline than in fruit stored at 4 degrees C. The concentrations of soluble sugars and titratable acidity decreased during storage at -1 degrees C, 4 degrees C, or 20 degrees C, but there was a peak of soluble sugars at a late stage of storage at the BFT (-1 degrees C). The fruit browning index was significantly and positively correlated (R-2 = 0.967) with ABA concentration. The decrease in ABA concentration in cold-stored fruit (at both -1 degrees C and 4 degrees C) inhibited ethylene production. Moreover, there was no significant correlation between CI in fruit and ethylene production. In conclusion, the decrease in ABA concentration reduced ethylene concentrations and inhibited the development of pulp browning, which resulted in an improved taste, but crisper fruit, when fruit were stored at the BFT (-1 degrees C)