Hi Everyone!
I wanted to share some invaluable information that Dr. Gmitter from the University of Florida shared with me. It's about the Rapid Evaluation System they used to optimize the growth and conditions necessary to induce flowering in young seedling trees. Some of this information is already known, discussed and applied by members, but hopefully this can still be a valuable resource for those who do not know already. I think it is especially valuable as we strive to create new cold hardy citrus hybrids, which can take many years and sometimes yield very good or disappointing results.
This is what he had to say:
"We used this approach several years ago to advance fruiting in seedling populations. We no longer use it because it is too labor intensive and costly for our program, with several hundreds or thousands of seedlings annually. Another reason we stopped was because even though we could get to see fruit and make selections quicker, we could not assess tree characteristics or yield potential, and the amounts of fruit produced were small, not enough to do any other essential evaluations such as harvests over time, post-harvest behavior, etc. Once we selected potential candidates, we still needed to propagate trees onto rootstocks and grow them off for further evaluations. And see my last paragraph below for more perspective on why we no longer follow this method.
I don’t know the scope of your breeding activities; however, it might be something useful to you if you are not dealing with large numbers of hybrids. But you should look at this system as a way of eliminating the obvious losers based on fruit quality attributes, and not necessarily as a way of selecting the winners. I’ve attached a brief research report to the agency that provided funding for our work with the RES, Rapid Evaluation System. You can see some photos and read descriptions of the project here.
OK, how we did this. We budded the new hybrids onto rootstocks, and these trees were planted at a close spacing of about 12 inches apart in the row. We had trellises to support the upright growth, as well as tall bamboo posts, one per tree. I have seen the breeding program in Japan using larger trees, with individual limbs topworked with buds of individual hybrids, and then growing these as single stalks. It was very complicated, as the different hybrids grew at different rates, and they tended to grow together, leading sometimes to confusion and harvesting budwood for propagation from the wrong hybrid. That’s also a challenge with the system we used, growing them one foot apart in the row on the trellis; the tops tended to grow together and if we went back to collect budwood after the fruit were gone, we would sometimes harvest the wrong materials.
The key to this approach is removing ALL side bud growth AS SOON AS IT APPEARS. As soon as the side buds push, because they are soft you can very easily remove them by hand, no need to cut; and while doing so you can also slough off any young thorns that are growing (though I’m not convinced that thorn removal was necessary, but our friends in Japan strongly recommended this step, so we did it). If you’re allowing your trees to develop “horizontal branches” and then cutting them, you’re not doing this right. Removing the side shoots ASAP forces the tree to grow upright and tall faster; that’s the goal, to get as far away from the embryo in the seed as possible. There are theories about a certain number of internodes away from the original embryo as the way to get away from juvenility. So, we were able to get our trees up to 10-12 feet tall in a year from planting, sometimes even faster. We usually propagated the budded trees in the greenhouse in he fall and winter, and began single stalking them immediately; so, we’d be planting 3-foot-tall trees next to the trellis in the spring, to get a jump on things. This might be a faster way for you than grafting onto existing older trees, if you have a greenhouse in which you can grow the young trees in through the winter. In the best cases, we had fruit on our trees the following year, just 12 months after planting in the ground!
Another important trick we used was to bend the treetops once they got up to ~12’ tall over to a lower wire on the trellis. Bending, you may know, is an old method in many fruit trees crops of inducing bloom the following season. And, in some cases we girdled the trunk at around 3 feet above the ground, usually in September to October (in Florida conditions). This was simply a single cut through the bark to the cambium, not removing a ring of bark, just enough to temporarily interfere with the movement of starch to the roots, thus accumulating in the upper part of the tree, another ancient technique to hasten the departure from juvenility. The trees go through a small shock, but the wound heals and they get back to business quickly. If you’re nervous about doing this, or concerned about transmitting or encouraging disease, then don’t do it; it’s not absolutely necessary. But the bending of the top is an important thing that should be done.
There are a few other things of which you should be aware. This technique works very well with some genetic backgrounds, but it is not universally effective. We had some crosses, as I mentioned, that fruited the next year, but other crosses simply didn’t respond at all, despite all our efforts at bending, girdling, etc. Second, although technically when the trees flower and set fruit we might say they are through juvenility. However, citrus trees and the fruit they produce require in many cases a few years of bearing to show their true potential as trees, and to reveal their true fruit qualities. There could be some trees that bear fruit that look rough (even ugly!), may be coarse internally, and of low quality (low juice and low Brix). You might be tempted to cut these and focus on the first “beauties”. But in so doing, you might be also cutting something that is going to be much better after it “settles down” than those early beauties."
I will attach some photos of the document that details this system further. I am also working on a video that describes this system and how we are using it as a tool for breeding and selecting. Enjoy!
Topic: The R.E.S. Method - Fruit From Seed in 1-2 Years (Read 1579 times)