Transformed apples: traits of significance to growers and consumers

The first report of transformed apple plants in 1989 raised expectations for new apple cultivars that would be better tasting, healthier and easier to grow. Although, many different traits have been now been introduced successfully into apple, no transformed cultivars have yet made it to commercial production. Most early reports on transformed apple described ‘proof of concept’ experiments involving the development of regeneration protocols, and the choice of appropriate promoters and selectable markers. More recently the focus has moved onto functional testing of traits of potential commercial interest. These traits can be grouped into two categories: horticultural production traits and fruit-focussed traits. Production traits of interest include bacterial, fungal and pest resistance, dwarfing, propagation, stress resistance, precocity, storage life and self fertility. Examples of fruit-focussed traits include novel health properties, flavour, reduced browning, colour, and reduced allergenicity. This review will consider reports of characters introduced into apple that are useful to growers and consumers, and looks toward future trends, targets and challenges