The Effects of Fruit Maturity and 1-Methylcyclopropene (1-MCP) Treatment on α-farnesene Metabolism in Scald Resistant and Susceptible Cultivars of Apple Fruit

Background: It was found that, climatic conditions and fruit ripeness are important factor for the occurrence and intensity of superficial scald. 1-MCP is an inhibitor of ethylene action in plants and inhibits many ripening related processes along with the production of ethylene and volatiles. Objective: Apples are often held for several months at low temperature either in air (RA) or in controlled atmosphere (CA) storage, therefore they are prone to the occurrence of a large number of physiological disorders. In this work an investigation was made in order to determine the effect of 1-methylcyclopropene (1.0 µl l-1) treatment on superficial scald development and α-farnesene metabolism on scald-resistant ‘Golden Delicious’ and scald-susceptible ‘Imperial Delicious ' apples. Methods: Fruits harvested on two dates and stored 24 weeks in refrigerated air storage (RA) at 0.5-1 °C. Peel tissue samples were taken at harvest after 6, 12 and 24 weeks. A reversed-phase high-performance liquid chromatographic procedure with UV detection at 232 nm and 269 nm has been used for the determination of α-farnesene and Ctols contents. Results: Scald symptoms were restricted to untreated control fruit of both harvests of Imperial as during storage period increased to 65 and 45%, respectively for the first and second harvest compared with no scald symptoms in those in Golden Delicious. At 1.0 µl l-1, 1-MCP completely eliminated superficial scald during storage period in Imperial apples. Large increases in peel tissue content of α-farnesene observed in untreated fruit of both harvest dates in Golden Delicious and Imperial cultivars. 1-MCP strongly decreased α-farnesene and conjugated trienols accumulation in treated fruit peel tissues at both maturity stages of two cultivars during storage. The results confirm the proposed role of Ctols in scald induction and indicate that α-farnesene production is strongly regulated by ethylene. Conclusion: In general, we conclude that only α-farnesene synthesis and its oxidation products (Ctols) levels in peel tissue could not be involved to the inherent nature of scald susceptibility or resistance in two cultivars tested.