Interactions of α-farnesene, conjugated trienols, and anti-oxidant activity during the development of superficial scald in ‘Fuji’ apple

Abstract

SummaryThe effects of harvest maturity and post-harvest treatment with ethephon or 1-methylcyclopropene (1-MCP) on the development of superficial scald in ‘Fuji’ apple (Malus × domestica Borkh.) have been investigated. The concentrations of α-farnesene, conjugated trienols (CTols), and hydrogen peroxide (H2O2), total anti-oxidant activity (TAA), and the activities of superoxide dismutase (SOD), guaiacol peroxidase (POX), and catalase (CAT) in the peel were measured during 24 weeks of storage of fruit harvested 3 weeks before (H1), or at (H2) commercial maturity. Fruit from H2 had a lower incidence and severity of superficial scald than fruit from H1. Scald development was further inhibited by the treatment of fruit with 1-MCP on either harvest date; however, treatment with ethephon inhibited the development of scald at H1, but increased it at H2. Fruit from H2 had lower concentrations of α-farnesene, CTols, and H2O2, but higher TAA and anti-oxidant enzyme activities than fruit from H1. 1-MCP treatment diminished the increases in the concentrations of α-farnesene, CTols, and H2O2 in fruit after both harvest dates. Compared with untreatd control fruit, the TAA in 1-MCP-treated fruit was higher at H2, but lower at H1. The effects of 1-MCP on anti-oxidant enzymes activities were only detected late during storage, with higher SOD, but lower CAT and POX activities in H1 fruit, and lower activities of all anti-oxidant enzymes in H2 fruit. Ethephon stimulated the accumulation of α-farnesene in fruit from both harvest dates, while the concentrations of CTols and H2O2 decreased following ethephon treatment at H1, but increased at H2. Pre-storage treatment with ethephon resulted in higher TAA and SOD activities in fruit from H1 at late storage, but had no effect on H2 fruit. Based on the data from all time-points, ethephon-treated fruit had higher CAT and POX activities at H2, but lower CAT and POX activities at H1 compared to untreated fruit. These results suggest that oxidative stress, leading to the development of superficial scald, depends on a combination of the production and scavenging of free radicals related to the interactions of α-farnesene, CTols, and anti-oxidant components.