Effect of storage temperature on viral RNA accumulation in Plum pox virus-infected Red Lyon plum fruit from the Central Valley of Chile

Abstract

Plum pox virus (PPV), the causative agent of Sharka disease, causes serious economic losses to the stone fruit industry. As PPV is not transmitted by seed, fruit from countries with Sharka present are considered low-risk for spreading the disease. However, there have been cases raising concerns about the safety of exporting fruit from countries with Sharka disease. Due to this, the generation of new scientific evidence becomes important to address these concerns. This study aimed to compare the relative accumulation of PPV viral titer between freshly harvested infected fruit with fruit subjected to cold storage, simulating transit conditions to export markets. During two consecutive seasons, the fruit was collected from a PPV-infected ’Red Lyon’ plum orchard, and divided into three treatments (T): freshly harvested fruit (T1); fruit exposed to cold (0 °C) for seven days (T2), and fruit exposed to cold (0 °C) for 15 days (T3). Semi-quantitative RT-PCR was used to estimate the viral titer; band density values obtained for products of amplification of a PPV genome fragment were normalized with the density values obtained from the constitutive gene nad5 and plotted relative to treatment T1, which served as a control for this purpose. The results showed a significant difference (p < 0.05) between T1 and other treatments. For the first season, the viral RNA reduction was of 50% in T2 and 61% in T3, compared to T1. For the second season, the corresponding RNA viral reductions were 45% in T2 and 56% in T3, compared to T1.