grafting pear trees
I have a Bartlett pear tree that I grafted an old sickle pear to several years ago. Did not prune tree last year and this year the tree had sickle pears. Is it possible that the whole tree will go to sickle pears
Shenandoah County Virginia
The tree will not revert back and forth but will produce fruit according to the wood from which it is growing. The limbs growing out from your graft, assuming it was viable, should produce Bartlett. If limbs remain from the rootstock (Seckle), or if they have grown up from below the graft union, then they will produce fruit according to the rootstock.
Here is a link to a University of Minnesota publication on grafting:
The following are good publications on growing pears and home tree fruit: