Differential Suppression of Ethylene Biosynthesis and Receptor Genes in ‘Golden Delicious’ Apple by Preharvest and Postharvest 1-MCP Treatments

Abstract

Harvista™, a sprayable formulation of 1-methylcyclopropene (1-MCP), has recently been developed for preharvest use on horticultural products, whereas SmartFresh™ is a widely used 1-MCP treatment for products after harvest. The effects of Harvista™ on apple fruit ripening when sprayed at different maturities and on expression patterns of ethylene biosynthesis and receptor genes during storage have been investigated. Harvista™ applied to on-tree maturing apple fruit at an average starch pattern index of 2.5 resulted in a higher at-harvest firmness value compared with those treated at a starch pattern index of 1.5 and 3.5. This indicates that the timing of the Harvista™ application is critical. An application of Harvista™ led to better postharvest fruit firmness retention as well as reduced ethylene production. In addition, both preharvest and postharvest 1-MCP treatments resulted in contrasting responses in the expression patterns of two ethylene biosynthesis genes and in differentially suppressing effects on four ethylene receptor genes. Furthermore, the combined application of Harvista™ + SmartFresh™ resulted in greater fruit firmness retention and longer ethylene suppression. The expression profiles of these genes during on-tree fruit maturation prior to Harvista™ application were also characterized. Different regulation patterns of receptor genes could contribute to differential effects by 1-MCP treatments. The potential roles of Harvista™ to manipulate the ripening process as well as the molecular mechanism influencing 1-MCP treatment efficacy are discussed.