Thunderstorm passed, nothing broken, nothing damaged. But this little cleft graft branch finally broke under the weight of its fruits. This plum scion was grafted two years ago (maybe3 years ago) on Santa Rosa. It has been growing weekly but stayed alive. I am overjoyed to see it bear fruits first time this year. But the branch was found broken this morning. I was going to blame the heavy storm we had last night. But, no , the storm didn’t do it. It broke right along the graft joints. Further exam the scion, the cutted edge, the V had very little new grown tissues that grow together into the rootstock. Its life support came from very little area of contact with the Santa Rosa. The grafting union had never healed well, thus the weak grown explained.
Hmm this might be a case of which came first, the chicken or the egg?
Was there little growth due to poor connection from graft union. Or was there little extra graft union connective tissue because of poor growth?
I suspect (not necessarily in this case, but more in general) that letting a slow growing graft fruit. Will do little for thickening up the grafted branch (and union) and thus lead to a weak structural graft union.
A tiny connection is usually enough to supply enough water/nutrients.
Large vegetative growth usually seems to strengthen graft unions, and thicken branches more, than a large fruit load.
If i look at the picture. It seems like it is mainly the originally grafted scion. I don’t see obvious spots where it goes from 1e year to 2e year to 3e year growth. I’m not saying it wasn’t grafted 3 years ago (i believe you 
) i just think it did not grew much length and thickness wise compared to the originally grafted scion. And that could explain the poor graft union healing/overgrowing.
This however is all mainly speculation on my part. So take it with a large pinch of salt.
I see quite a few latent/dormant buds on that broken of twig. Maybe you could T or chip bud them? I also think that a graft grown from a T or chip bud, runs a lower risk of braking of from fruit weight/poor connection. Unless you bud a flower bud that is.
But if a chip bud grows enough twig to make flower buds. It’s usually more than healed/connected enough structurally to bear the extra weight.