Nothing Stays The Same
Posted on: Monday, July 28, 2014 by Darryl McCullough
Last week's post introduced the ongoing controversy about whether the Hak-Ip and Sweetheart varieties of lychees are one and the same. Some say yes, others say no. Some say recent UF genetic research shows they are the same, others say that same research shows they are different. As we await the publication of the research to see for ourselves what it says, it's of more than just passing interest to think about what we mean by a "variety".
As those in attendance at the July MRFC meeting will recall, speaker Steve Cucura explained that grafting and airlayering need not create perfect copies. The branches of a tree can be different genetically, sometimes subtly and sometimes with quite noticeable effects. A thornless variety can throw a thorny branch, a variegated shrub can go plain. Either in grafting or airlayering, differences from branch to branch allow for genetic variation of the resulting trees.
This is good news, since it opens the possibility of improving a variety by thoughtful selection of scions. But it also creates an interesting pitfall. Lychees fruit on the end of the branch, and Steve pointed out that for a producer who sells both lychee fruit and propagated lychee trees, the natural tendency would be to take as scions the branches that are not carrying the pricey fruit. That is, to favor poorly fruiting ones for propagation! Steve takes measures to avoid this, but I wouldn't bet that every other producer in the world is quite so conscientious.
The bottom line is that even when not accidentally mis-labeled or otherwise confused, trees bearing the same cultivar name are just very close relatives, not identical copies. In the case of lychees, a genetic study of the variation was conducted some twenty years ago. I'll report on those results next week