Introduction
The
purpose of commercial storage of fruit is to lengthen shelf-time and
maintain the taste of pulp. The current postharvest storage technologies
mainly focus on a combined utilization of storage environment factors
such as temperature, modified atmosphere and chemicals, and among them
temperature control is the most widely used method for fruits and
vegetables during shelf life. Although cold conditioning is a virtually
irreplaceable method used to prolong the postharvest quality of
horticultural products, chilling injury (CI) is triggered in tropical
and subtropical fruits which are sensitive to low temperature
(Teklehaimanot, 2004). CI plants have a
series of cellular changes, including ethylene synthesis, membrane
fluidity and cytoskeletal rearrangement, resulting in internal browning
(IB), flesh breakdown, lack of juiciness, and loss of flavor, which
seriously affects the commercial values of fruits
(Cramer et al., 2011).
With the climatic change of global warming, high temperature stress
becomes a major plant stress affecting plant cellular homeostasis, crop
growth and development (Tubiello et al.,
2007). Plants have evolved a series of responses to raised temperature
linked with heat stress proteins (HSPs), heat stress factors (HSFs), and
phytohormones such as abscisic acid (ABA), salicylic acid (SA) and
ethylene (Kotak et al., 2007). Besides,
the effects of high temperature have been reviewed on its inhibition of
ethylene production, control of postharvest diseases and reducing CI in
many fruits and vegetables (Barkaigolan and
Phillips, 1991; Lurie, 1998;
2005). In kiwifruit, high temperature
stress controls fruit ripening by inhibiting ethylene production and
signaling sensitivity (Antunes and
Sfakiotakis, 2000), similar to studies on apple
(Lurie and Klein, 1990) and tomato
(Lurie and Klein, 1991). However, decline
of fruit firmness and increase of ethylene production were observed for
banana fruit during storage at high temperature
(Yan et al., 2011). Overall, numerous
studies focused on how to reduce CI and on the effect of heat treatment
on ethylene metabolism, all of which showed that temperature is vital
to fruit storage. However, limited studies have considered the
influences of high temperature for shelf life after transient cold
conditioning.
Peach (Prunus persica L. Batsch) has highly perishable fruits
that decay quickly at ambient temperature. Although refrigeration is
used to maintain flesh quality and prolong shelf-time, peach is highly
sensitive to low temperature, resulting in CI. The major symptoms of
postharvest CI are internal browning, mealiness or wooliness, and flesh
bleeding or internal reddening with physiological disorders
(Brummell et al., 2004;
Lurie and Crisosto, 2005). In previous
studies, heat treatment has been applied prior to cold storage to
prevent or alleviate CI by acquiring CI tolerance in response to heat
shock (Saltveit, 1991;
Ferguson et al., 2000;
Paull and Chen, 2000;
Budde et al., 2006;
Wang et al., 2006;
Peng et al., 2009;
Zhang et al., 2011). However, information
is much less about high temperature conditioning after cold treatment in
peach fruits.
In this study, we performed comparative transcriptomic analysis
of postharvest peach fruits between high temperature (HT: 35
°C) and common temperature (CT: 25 °C) after a pre-storage at 5 °C for 2
days, and combined the comparison results with measured physiological
changes to comprehend the process of peach fruit decay. This study
provided new insights into the molecular mechanisms of temperature
response during fruit shelf life and offered novel clues for developing
the fruit storage technologies in practice.