Involvement of enzymatic browning and peroxidase activity as resistance mechanisms in Golden delicious apples
Valentines M.C.; Vilaplana R.; Uasll J. and Larrigaudiere C.
5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004, p.105
2004
บทคัดย่อ
Involvement of enzymatic browning and peroxidase activity as resistance mechanisms in Golden delicious apples
In this study different experiments were carried out to determine of enzymatic browning is involved in the resistance of Golden Delicious apples against
Penicillium expansum. For this prupose and in order to have samples with different sensitivity to pathogen, fruits were picked at different maturity stages. Immediately after harvest, fruits were inoculated with a conidial suspension (104 conidia mL
-1) of
P. expansum and the percentage of altered fruits determined after 7 days of incubation at 20°C. Browning potential was determined in situ using a colorimetric method and determining the changes in DE. Concomitantly, the activity of the browning-related enzymes polyphenoloxidase (PPO) and peroxidase (POX) were determined for each maturity stages. To better determine the specific role played by these enzymes, fruits were also previously treated before inoculation with ascorbate (to inhibit the browning process) or with their specific substrates (to activate this process).
For each maturity stage a clear correlation was found between browning capability and disease resistance. In this process PPO and POX activity were not limiting but substrate availability was clearly determining. When incubated with ascorbate or 4-methyl-pyrocatechol a clear increase in sensitivity to pathogen was observed. In contrast pre-incubation with guaiacol led to increased resistance especially in the less mature fruits. Collectively these results provide evidence that enzymatic browning and POX enzyme activity may be considered as important factors involved in defence mechanism in apples.