A gentleman came by yesterday who let me know he is growing a mature pear orchard about a mile from here that seldom produces. He has lots of different pear trees. We spoke a while and he walked the orchard. He was very shocked to see my trees carrying fruit when we had a mere 7 inches of rainfall this year. Wild callery rootstocks are tough and do seem very good at surviving which is much of what I use. The pyrus betulaefolia rootstock are very resistant to harsh conditions as well but I’ve not used those as long. Ohxf… are doing ok. Harbin seems slightly more susceptible to drought damage. The evidence is not conclusive.
Great information of your actual observations and comparisons. TY for posting this.