Mar 9, 2015Honeycrisp: A case of mistaken identity
Honeycrisp is arguably the most popular new apple cultivar around. Its exceptionally crisp and juicy texture set it apart from its competitors. According to breeders’ records, Honeycrisp resulted from a cross between Macoun and Honeygold made in the 1960s at the University of Minnesota. For years, people tasted the Honeycrisp apple and attributed its promising characteristics to genes inherited from its two putative parents. However, DNA evidence published in 2005 has shown that neither Macoun nor Honeygold are parents of the Honeycrisp apple. It has been revealed that Keepsake, another apple developed at the University of Minnesota, is likely one of the parents and the other parent remains unknown.
Breeders scrutinize potential parents carefully when deciding which cultivars to cross together in the making of a new cultivar. The mistaken identity of Honeycrisp seems to suggest that such scrutiny is superfluous, that the choice of parent is irrelevant and that the success of a cultivar has nothing to do with the genes of its parents. After all, Honeycrisp is one the world`s most popular cultivars but its parents were not even chosen on purpose!
This suggestion is ridiculous. We know that offspring resemble their parents. If your mother and father are both tall, chances are that you will be tall as well. The same applies for many traits in apples. So we know that the choice of what two apples to cross together has an influence on the traits of the resulting offspring. Thus, we argue that it is not the case that scrutiny is superfluous, rather that the scrutiny in traditional apple breeding is limited by the measures employed. The fact that Honeycrisp, one of today’s most successful commercial cultivars, was generated essentially from random parents suggests that the metrics used by breeders in selecting parents are sometimes ineffective. Of course, extensive evaluations were required to choose Honeycrisp as the most promising from among its hundreds of siblings. But any apple breeder will admit that their evaluations involve lots of noisy and subjective measures. Could it be that one of Honeycrisp’s siblings would have had equal success in the marketplace?
We are dedicated to improving the suboptimal toolkit that apple breeders currently have to work with. Apple breeders are dedicated to improving our food: they spend decades evaluating tens of thousands of apple trees that will never attain commercial success in order to pick out the one tree that is worthy of further propagation. By measuring the natural genetic diversity among apple cultivars and determining how this diversity affects commercially important traits, our lab aims to optimize the choice of which apples to cross together. The DNA from the resulting offspring will also be sequenced at the seedling stage, while the trees are small and still in the greenhouse. At this stage, we aim to predict from their genetic information how they will perform as adult trees. Seedlings with undesirable genetic profiles will be discarded, and only the seedlings with the most promising genomes will be planted out in orchards and be evaluated extensively by breeders. This process is called marker-assisted selection and it does not involve producing a genetically modified organism (GMO). We simply use DNA information to enhance traditional breeders’ toolkits, providing them with natural diversity that has been pre-screened. This pre-screening promises to significantly reduce the enormous effort and cost that goes into evaluating tens of thousands of commerically useless trees. “Genetics” is often considered a dirty word in agriculture because of the public`s perception of GMOs. But DNA information promises to help breeders more efficiently and cost-effectively develop tasty cultivars that require less chemical input. There will be no more mistaken identities in the age of genomics.
– Sean Myles, Dalhousie University