Grafting citrus to sapote

[Ps6000]

Can someone help me understand something.  White sapote is a distant relative to Citrus but is reportedly not close enough to support grafting.  How is that determined?  How would one figure out what species would be close enough to graft with citrus? Stone fruit is close enough for the “fruit cocktail” trees, I have heard of people grafting pears and apples.  Where in the families tree is close enough?

[FloridaManDan]

Generally speaking, species under the same genus may be genetically similar enough for graft compatibility. White sapote (genus Casimiroa) and Citrus are too distant, whereas peaches, plums and cherries all fall under the genus Prunus and can be grafted as a cocktail tree.

[drymifolia]

There's no bright line rule, in part because the concepts of "species" and "genus" are blurry and based on limited information. Even genetic analysis is an imperfect science that rarely compares whole genomes, and most species labels predate that kind of analysis.

Avocado is only graft compatible with about half the species in its genus, Persea, for example. But within the rose family, Rosaceae, it's very common for things in different genera to be graft compatible. Loquat (Eriobotrya japonica) and quince (Cydonia oblonga) are graft compatible, for example, as are things like rowan (Sorbus aucuparia) and European pear (Pyrus communis).

The only way to know for sure whether two species are compatible is to try, especially if you can't find any reports of them being incompatible. Many things have never been tested because other things already work well enough that no one has bothered trying more distant relatives.

[Galatians522]

If you are looking for the most distant yet graft compatible combination with citrus, Wampee is suposely partially graft compatible with citrus. The resulting plant is fairly weak but I have read reports that the combination can last 10-15 years. As has been mentioned, there is no way to know what is graft compatible without trying (or learning from someone who has). Typically, the closer related, the better the chances for compatibility. Oddly enough, however, there are some unusual circumstances where things that are more distantly related (or at least appear more distantly related) are more compatible. For example, not all citrus is compatible with Fortunella and Poncirus, but some citrus is partly compatible with Clausena??? Based on the length of time the graft survives.

[Ps6000]

The only way to know for sure whether two species are compatible is to try, especially if you can't find any reports of them being incompatible. Many things have never been tested because other things already work well enough that no one has bothered trying more distant relatives.

The worst that could happen is failure.  Thanks for the reply.  Probably worth giving it a shot.

[Ps6000]

If you are looking for the most distant yet graft compatible combination with citrus, Wampee is suposely partially graft compatible with citrus. The resulting plant is fairly weak but I have read reports that the combination can last 10-15 years. As has been mentioned, there is no way to know what is graft compatible without trying (or learning from someone who has). Typically, the closer related, the better the chances for compatibility. Oddly enough, however, there are some unusual circumstances where things that are more distantly related (or at least appear more distantly related) are more compatible. For example, not all citrus is compatible with Fortunella and Poncirus, but some citrus is partly compatible with Clausena??? Based on the length of time the graft survives.

Thanks for this insight.  Looks like I have an experiment coming up, with a high likelihood of failure.

[Epiphyte]

personally, i spend lots of time looking at phylogenetic trees / cladograms to try and decide whether it's worth trying to graft two species.  the less distance between the two species on the cladogram, the more likely that they can be grafted, and crossed.  but it's not a perfect rule because scientists don't use compatibility to determine relatedness.  i recently posted about this in the fig forum... taxonomy, cart or horse. 

[drymifolia]

personally, i spend lots of time looking at phylogenetic trees / cladograms to try and decide whether it's worth trying to graft two species.  the less distance between the two species on the cladogram, the more likely that they can be grafted, and crossed.  but it's not a perfect rule because scientists don't use compatibility to determine relatedness.  i recently posted about this in the fig forum... taxonomy, cart or horse.

And there's been some talk recently of serious problems with the methodology used to produce those charts from genetic analysis. Especially the most popular method, which looks for fragments of genes and draws conclusions about the entire genome from those fragments. It appears there were some incorrect assumptions underlying that process, and many of those trees may be to be redrawn once whole genome comparisons can be made.

[Artocarpus]

Sometimes even trees of the same species are not 100% compatible. About 25 years ago I grafted a few longans on longan seedlings just for curiosity. All survived and still alive but only 1 out of three had a healthy graft. This year I cut down the worst of the 3. When cut across the graft looking at the cambium it looked like a zig zag pattern not a continuous uninterrupted normal growth. The graft union from the outside also looked unhealthy with a corky bark. I should have documented it for educational uses but turned it into bio char instead.
The bottom line is that graft compatibility is something that can sometimes take decades to evaluate for long living trees. Moreover, there is an ethical line in claiming what has been grafted will stand the test of time if you are selling a grafted tree species that has not been proven. So experiment away but hold back on the conclusion for a bit and have fun.