Cell-wall and structural changes during softening in two Actinidia chinensis var. chinensis genotypes with contrasting softening rates

Success of a new kiwifruit (Actinidia spp.) cultivar requires not only good taste, but also a storage life that allows it to remain firm during storage and transport to distant markets, and the subsequent ability to soften and ripen once it reaches the consumer. During the ripening process, it is changes in the chemical composition and structure of the cell walls that enable fruit to soften. Within kiwifruit, there are closely related genotypes that show large differences in softening rates. We compared two such genotypes with different softening rates to investigate the chemical and structural basis of fruit softening. Compositional analysis of cell walls during softening showed differences in monosaccharide composition between the genotypes at the same developmental stage. Structural analysis showed differences in the way that the cell wall changed during softening. This indicates that the rate of softening may not be just an effect of increased enzyme activity, but that there may be fundamental differences in the cell-wall composition between genotypes that have different softening rates. Extending knowledge of cell-wall components and structural properties during softening can be applied to identify chemical markers for breeding kiwifruit to enable early-stage selection of genotypes with a preferred softening rate.