Materials and methods
Plant
materials and treatments
Red flesh peach (Prunus persica L. Batsch cv. Tianxianhong)
(He et al., 2010) fruits with consistent
color, shape and weight were harvested at commercial maturity from an
orchard in Xiaogan, Hubei province, China. Uniform fruits without visual
defects were selected and kept at 5 °C for 2 days after the day of
harvest. Then, these fruits were randomly divided into two groups. One
group was stored at CT for 7 days, and the other was stored at HT for 7
days. During shelf life, fruits were sampled at day 1, 2 and 3 as early
stage as well as day 5, 6 and 7 as later stage. For each sampling point,
sarcocarp was extracted and randomly distributed into two biological
replicates. Then, mesocarp was sliced, frozen in liquid nitrogen and
stored at -80 °C for further study.
Measurements ofphysiological
changes
Some physiological parameters were measured for each sample during
storage. GY-2 fruit hardness tester
with a 3.5-mm-diameter head was applied to measure the pulp firmness of
fruit without peel. Six peach fruits from each sample were selected, and
7 points evenly distributed over each fruit were examined and the mean
of the measured values was calculated and used. To
detect
ethylene production, 1 kg of fruits from each sample were selected and
preserved in a sealed box at the same temperature for 6 h, then 1 ml gas
sample was collected to measure ethylene production using
gas chromatography (Agilent
Technologies 7890A GC System, USA) with 3 biological replicates.
The
gas chromatographic (GC) analysis of ethylene used GC Columns (30 m ×
0.530 nm × 3.00 µm), and oven, inlet and detector temperatures were 40
°C, 250 °C and 250 °C, respectively. The ethylene standard curve was
plotted with the gradients of 5 concentration values to identify the
ethylene production rate. The 1-aminocyclopropane-1-carboxylic acid
(ACC) synthase and ACC oxidase were extracted to measure their
activities using conventional
method.