When I made the grafts, I actually top-worked trees that were roughly three inches in diameter. By starting with such large stock trees, it is not surprising that these grafts set a crop in their third year. In comparison, the mother trees are 21-years-old and are 10 to 12 inches in diameter.
I was able to look at 3 clones from the breeding project. KT143 and KT149 are crosses of Pawnee and Major. KT334 is a hybrid of Pawnee and Greenriver. All three clones have been consistent producers of early ripening pecans.
It is interesting to note that all young grafts produced smaller nuts than their mother trees. I've seen this phenomenon numerous times over the years. In testing new pecan cultivars, you just don't see the full potential (warts and all) of a pecan cultivar until the tree has grown to at least 10 inches in diameter.
I also cracked a sample of nuts from each young graft and their corresponding mother tree to check for differences other than size. With KT143, the kernels from the young graft looked very different than kernels from its corresponding mother tree. Kernels from the grafted tree were shorter, almost round in shape, and darker in color. These differences in kernel appearance can be attributed to a young tree's struggle to compete with the ground cover for water and nutrients.
The KT149 kernels, like the inshell nuts, were very close in size to kernels extracted from nuts borne by the mother tree. The lower percent kernel I found from young tree nuts were probably due to kernel defects caused by stinkbug feeding. In managing my orchard, I only apply a full spray program to trees with a full harvestable crop. Since they weren't bearing enough of a crop to justify harvesting, the young KT149 trees did not receive the sprays needed to control stink bug.
When comparing kernels from young KT334 trees to kernels from the mother tree, the nut meats look identical. Surprisingly, the numbers indicate that the young trees actually produced nuts with higher percent kernel. This might be a sign that KT334 can fill kernels completely under various growing conditions or an indication that the tree never sets enough nuts to cause kernel filling problems (inherit low yields). I need to take a closer look next year.
I wanted to share these pictures from our pecan breeding work to give you some idea why it takes slow long to develop new pecan cultivars. Weighing and cracking nut samples are among the easiest measurements to record but it takes many growing seasons to learn how cultivars hold up under widely varying weather conditions. In addition, things like alternate bearing, disease resistance and susceptibility to cold injury usually aren't revealed until the trees are at least 25 years old. If I have learned anything from working with new pecan cultivars for the last 37 years it is that patience and caution are needed to avoid costly cultivar mistakes.