The peach 1-aminocyclopropane-1-carboxylic acid synthase isogene, Pp-ACS1, is required for fruit softening

The fruit of melting-flesh peach (Prunus persica (L). Batsch) produces increasing levels of ethylene, and the flesh firmness softens rapidly during the ripening stage. On the other hand, stony hard peaches barely soften on the tree or after harvest, although the fruit changes colour normally, contains highly soluble solids and has good flavour (Haji et al., 2001). It has been assumed that a low level of ethylene production by stony hard peach is responsible for the inhibition of fruit softening, because exogenous ethylene softens them effectively (Hayama et al., 2003; Haji et al., 2003).