Answer: Your tree is still young enough to do some training. To make the trunk grow thick enough to support branches you simply need to prune the branches back so they are not so long. Cut them back by one third to one half and they will branch out and thicken the canopy. Each time you "head back" the branches they will become thicker and sturdier - and so will the trunk as it matures. In a few years your tree should have a nicely shaped crown and the trunk will be sturdy enough to hold up the branches, even when they are thick with fruit.
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