Do any of you know anything about the genetic origins of the Shiro Plum or about whether there are multiple strains being passed around under the Shiro name? It seems like I remember seeing it mentioned somewhere that it has a lot of Prunus caricifera in it’s genetic makeup.
Here’s why I’m asking. A FB friend of mine has several mature Shiro plum trees that are doing well for him in Zone 9A Southern Mississippi. It strikes me to be surprising that an Asian plum from the Burbank breeding program would be disease resistant enough to take that sort of climate for very long. Anyway I figured that if it can survive coastal Mississippi that it should be able to take a Georgia 8b climate as well. I grafted two twigs into two branches of a Robusto plum sapling in my orchard. These twigs have since sprouted and are growing well. But the leaves are surprising the heck out of me. They do not look like Asian plum or maribailan plum leaves at all. They look like Chickasaw plum leaves to me. In fact apart from having totally green softwood twigs as opposed to red ones, the shoots are nearly indistinguishable from Robusto and the various improved Chickasaw varieties that I have grafted into this particular Robusto.
I’ve decided to explore whether there is any Chickasaw plum in the pedigree of Shiro. So far I haven’t turned up any information on this one way or the other. But I have found numerous photos of Shiro on the internet. In all cases the plums are canary yellow, but in some of the photos the leaves are long and slender lick Chickasaw plum leaves. In other photos they are oval and more like what you would expect from Prunus salicina or Prunus caricifera. This makes me think that there are two distinct strains out there under the same name with one having a lot of Chickasaw in it’s genome and another (guessing the original) without the Chickasaw genes. I’m just curious what others know about Shiro both with respect to its genetic history and with respect to there being multiple strains. If anyone has any useful anecdotal info on its resistance to disease that would be useful as well.
Also if I should decide to graft Shiro onto it’s own root should I go with an improved Chickasaw rootstock like I would with an Asian type. Or should I treat it more like a cherry plum and graft it onto Mariana. (Not that I have any Mariana suckers left this season.) God bless.
Marcus