Ethylene Intensifies but is not a Requirement for Methyl Jasmonate- Enhanced Anthocyanin Synthesis by ‘Fuji’ Apple Fruit

Exogenous methyl jasmonate (MJ) stimulates anthocyanin accumulation in apple (Malus sylvestris var. domestica) fruit peel. Anthocyanin synthesis in some apple cultivars reportedly is also stimulated by exogenous ethylene, however, the role of ethylene action in regulation of anthocyanin synthesis in apple fruit is unclear. MJ enhances ethylene sensitivity in various plants, therefore, studies were conducted to evaluate the role of ethylene and MJ in stimulation of anthocyanin synthesis in immature ‘Fuji’ apple fruit. Following ethylene and MJ treatments, fruit were exposed simultaneously to UV-B and visible light, then pigments were extracted and analyzed by reverse-phase high performance liquid chromatography. Treatment with MJ alone enhanced anthocyanin accumulation, including idaein, the major anthocyanin in apple fruit. Anthocyanin accumulation was further stimulated by treatment with MJ + ethylene. Treatment with the ethylene action inhibitor 1-MCP followed by MJ reduced red coloration over MJ alone. Treatment with ethylene or 1-MCP alone, or ethylene+1-MCP had little effect on anthocyanin accumulation. Chlorogenic acid synthesis was also enhanced by treatment with MJ or ethylene, however, treatment with 1-MCP alone or with MJ decreased chlorogenic acid content. MJ enhanced production of hyperin, the major quercetin glycoside in peel tissue, while ethylene and 1-MCP had no effect on quercetin glycoside content when applied alone or in any combination. ß-carotene synthesis was enhanced following MJ treatment, stimulated further by MJ plus ethylene, but was not enhanced by ethylene alone. The results indicate a synergistic response between ethylene and MJ for stimulation of anthocyanin synthesis. Treatments with ethylene alone or 1-MCP indicate a limited role for ethylene action in regulation of red color development by immature ‘Fuji’ apple fruit. INTRODUCTION Methyl jasmonate [methyl 3-oxo-2-(2-pentenyl)cyclopentane-1-acetate] application elicits many wound related responses (Creelman and Mullet, 1997) including anthocyanin synthesis (Francheschi and Grimes, 1991). Exposure of apple fruit disks (Kondo et al., 2001) and whole apple fruit to MJ (Rudell et al., 2002) leads to increases in peel anthocyanin levels. As with the cyanidin glycosides, quercetin glycosides, chlorogenic acid, and ß-carotene also increase with MJ exposure (Rudell et al., 2002). Additionally, MJ application to pre-climacteric fruit can promote increases in ethylene synthesis as well as increase ethylene sensitivity (Fan et al., 1997). Anthocyanin synthesis in apple fruit can also be stimulated by treatment with ethylene or the ethylene releasing compound, ethephon (2-chloroethyl phosphonic acid) (Blanpied et al., 1975; Faragher and Brohier, 1984; Gomez-Cordovés et al., 1996). As would be expected, application of aminoethoxyvinylglycine (AVG), an ethylene synthesis inhibitor, leads to reduced anthocyanin accumulation (Wang and Dilley, 2001). While reducing degreening in ‘Golden Delicious’ (Fan and Mattheis, 1999), the effects of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) on anthocyanin synthesis has Proc. XXVI IHC – Deciduous Fruit and Nut Trees