The appearance of a fruit is a significant factor in determining consumer preferences, with smooth skinned kiwifruit being of particular interest. Smooth skinned fruit typically have a living epidermis, comprised of a single layer of cells. This living layer can be more susceptible to physical damage than the skin of hairy kiwifruit, which have a skin comprised of several layers of dead cells. We have therefore aimed to increase our understanding of the skin structure and the interrelationship between smooth and hairy skinned kiwifruit, and the genetic basis of skin type, by investigating the variability of skins in an experimental hybrid population between smooth and hairy skinned forms. We have also investigated the way in which the skin of smooth skinned kiwifruit responds to environmental conditions, by artificially simulating natural damage.
A combination of scanning electron microscopy and light microscopy was used to observe the skin structure and cellular organisation. From the experimental population, it appears that a smooth relatively hairless skin is likely to be dominant. Further crossing produced a wide variety of skin types, ranging from a smooth surface with a simple epidermis through a range of modifications of cell types and hairiness, to rough surfaces with thick layers of dead cells. Sometimes both smooth and rough types occurred on the same fruit. After artificial damage, fruit lost hairs from the skin surface, had breaks in the epidermal layer, and variable amounts of compression of the epidermal and sub-epidermal layers. After a period of several days’ cell proliferation, cell collapse and cellular darkening were observed. This response can be related to the more advanced natural blemishes seen in harvested and stored kiwifruit.