Summary: The objectives of this project were: 1. Characterize apple fruit ripening characteristics including ethylene evolution for 6-10 cultivars at defined developmental stages. 2. Investigate cultivar-specific fruit softening rate and ethylene regeneration in fruits treated with 1- MCP. 3. Examine expression patterns of MdACS3 and other ethylene biosynthesis and perception related genes during fruit ripening and in response to 1-MCP treatments (including Harvista on-tree spraying). 4. Explore the potential polymorphism at the MdACS3 locus for potential functional molecular marker generation, based on gene expression results.