SundanceTM is a modern disease resistant apple, which was first selected from a breeding programme in the 1960s and introduced in the early 21st century.
The following excellent article describes the origins of this apple in more detail: www.hort.purdue.edu/newcrop/pri/sundance.pdf. Of particular interest is the pedigree diagram which shows the direct relationship with Golden Delicious, along with the more complex parentage necessary to incorporate the gene for scab resistance which occurs naturally in the crab apple Malus floribunda. This is a good illustration of the challenge facing anyone trying to develop a scab-resistant apple, in effect it is a matter of retaining the scab resistant gene whilst breeding out the other less desirable characteristics of the crab apple (small size and acidic flavor) and replacing them with better qualities from high quality apples such as Golden Delicious.