Abstract
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 °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.
Highlights
The amounts and types of pigments in plant tissues are responsible for the colors of plants.In European pear (Pyrus communis L.) fruit, there are three different colors expressed at the mature stage; green, red, and brown
In ‘Grand Champion’ pears, ethylene treatment promoted ethylene production, and fruit treated with ethylene produced more ethylene than did the control fruit
Ethylene production was suppressed by 1-MCP treatment throughout the experimental periods in both ‘Gorham’ and ‘Grand Champion’ pears
Summary
In European pear (Pyrus communis L.) fruit, there are three different colors expressed at the mature stage; green, red, and brown. The development of yellow color in green pears results from the masking of carotenoids with chlorophyll at harvest, as well as unmasking by chlorophyll degradation, as reported in the fruit and/or leaves of various plants, including pears [1,2]. Terrestrial plants have evolved lipophilic barriers that protect against dehydration, physical damage, pathogens, and diseases. Plant primary organs, such as young stems and leaves, are protected by the cuticle, a lipophilic extracellular polymer membrane composed of cutin and waxes. Secondary (mature) stems and roots, tubers, and healing tissues are protected by cork mainly composed of suberin [4]. The suberized exocarp of potato (Solanum tuberosum) [6] and the bark of cork tree (Quercus suber) are the best characterized examples
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