Ripening Characteristics and Pigment Changes in Russeted Pear Fruit in Response to Ethylene and 1-MCP

Ripening characteristics and pigment changes were investigated in 'La France', 'Gorham', and their russeted sports 'Gold La France' and 'Grand Champion' pears. Fruit were harvested at commercial maturity and ripened at 20 degrees C. In all cultivars, fruit softening was concomitant with a burst in ethylene production. Interestingly, such changes were delayed in russet pear when compared with their wild-types. Chlorophyll level in russet pear at harvest was the same as in the wild-type. In 'Gorham' and 'Grand Champion' pears, its level rapidly decreased during ripening. Ethylene or 1-methylcyclopropene (1-MCP) did not affect the color and pigments in 'La France' and 'Gold La France' pears. In contrast, in 'Gorham' and 'Grand Champion' pears, chlorophyll degradation was suppressed by 1-MCP treatment, but not completely. These results suggested that chlorophyll degradation was regulated by both ethylene-dependent and ethylene-independent means. The influence of ethylene on the expression of chlorophyll-degradation-related genes seemed to be similar in both russet and wild-type. The Stay green-1 gene was stimulated by ethylene and suppressed by 1-MCP treatment. In contrast, little effect of ethylene or 1-MCP was observed on chlorophyllase 1, pheophytinase, pheophorbide a oxygenase, and NYC1-like genes.