Relative humidity regimes modify epicuticular wax metabolism and fruit properties during Navelate orange conservation in an ABA-dependent manner.

Relative humidity (RH) during conservation and the chemical composition of epicuticular wax layer are factors that determine fruit quality and weight loss. This study investigates the influence of RH on the epicuticular wax metabolism during citrus fruit storage, and how it is affected by abscisic acid (ABA). Low RH conditions increased alcohols and fatty acids abundance, mainly due to accumulation of docosanol and lignoceric and cerotic acids. Low RH also decreased terpenoids and nonacosane and hentriacontane contents, the most abundant alkanes. Consequently, the alkane/terpenoid ratio was decreased concomitantly with fruit weight loss and cuticle permeability increments. ABA treatment differently mediated wax compositional changes at high or low RH. At low RH, ABA attenuated the increase in fatty acids and enhanced the decrease in alcohols and the accumulation of terpenoids, mainly affecting lignoceric and cerotic acids, docosanol, α-amyrin, sitosterol, friedelin and friedelanone contents. These trends were inversed under high RH conditions.