Tuesday, August 25, 2015

That tree is not a Giles!

   Years ago, we started a scionwood orchard to produce high quality scions for growers to graft onto their seedling pecan trees.  When we established this orchard, we took great care to graft with scions from known trees that were true to cultivar.  But several years ago, I noticed that one of the trees marked "Giles" (tree 17 in row 6) in the scionwood block ripened well ahead of all the adjacent Giles trees. Even though the nuts are roughly the same size and shape, I noted that nuts collected from the tree we are now calling, SWB617, has a different shuck appearance. Giles nuts have prominent wings along shuck sutures. SWB617 does not. (photo above).

     I cut open a Giles and a SWB617 nut yesterday to check on nut development (photo at left). Wow, what a difference. Giles was still in the water stage and SWB617 had packed the inside of its shell with kernel.
    The question is--where did this early ripening tree come from? I looked at the trunk of the tree and it certainly looks like it was grafted near ground level just like all the rest of the Giles trees in the same row. But how could one piece of unknown scionwood get mixed up into a whole bag of Giles wood? Not only that, SWB617 doesn't look like any cultivar we have on the farm. I'm now convinced that the original Giles graft died and the seedling root grew up to take its place. That would make SWB617 an open-pollinated Giles seedling (we used Giles seedlings to start the planting).
   Last year, SWB617 produced a nut that averaged 5.79g and had 56.61% kernel. For comparison, Giles averaged 6.36g and produced 52.66% kernel. SWB617 matured during the last week of September in 2014 and showed little or no scab infection. In 2015, SWB617 has some scab but not as bad the scab found on adjacent Giles trees. In contrast, SWB617 had more powdery mildew on nuts than found on Giles nuts.  Because this tree ripens early, it will definitely be worth watching. I've even grafted a few more trees of this seedling to see how it acts as a grafted tree.
   So in the future, when I mention a tree called SWB617 you will know a little of its background and why I labeled it based on the location of the tree at the research station--Scion Wood Block row 6 tree 17.