PHENYLALANINE AMMONIA-LYASE AND ACCUMULATION OF PHENOLIC COMPOUNDS IN THE ETHYLENE-INDUCED TOLERANCE TO RINDSTAINING IN ´NAVELATE´ FRUIT

The orange fruit cultivar ‘Navelate’ is prone to develop postharvest rindstaining (RS) during storage at non-chilling temperatures.
Ethylene has been shown to protect citrus fruit against RS but the mechanisms associated with the ethylene-induced tolerance to this disorder are unknown.
In this study we have examined the effect of applying ethylene, before or during holding of ‘Navelate’ fruit under postharvest conditions inducing RS (22°C, 90-95% RH), on changes in the activity of the enzyme phenylalanine ammonia-lyase (PAL), total phenolic content and fruit quality.
PAL activity increased with the development of damage in the albedo and flavedo of fruit maintained under air.
Exogenous ethylene treatments, which efficiently reduced RS incidence, increased PAL activity as well as the levels of total phenolic content in the flavedo and in the pulp.
However, these levels were not maintained after prolonged storage, either in fruit kept continuously under ethylene or in those transferred to air.
The global results indicate that the induction of the enzyme PAL and of subsequent phenylpropanoid compounds may play a role in reducing the development of RS symptoms and might be a part of the mechanisms involved in the beneficial effect of ethylene in protecting citrus fruit against this physiological disorder.

V International Postharvest Symposium

J.F. Cajuste, M.T. Lafuente

citrus, orange fruit, peel pitting, physiological disorders, quality

https://doi.org/10.17660/ActaHortic.2005.682.154