That is correct, from that perspective, it is not 100% the same tree.

An individual tree defined as 100% = Phenotype + Genotype.
Phenotypically, it is not the same tree compared to the one on its own roots, even if it has retained 100% DNA in its tissues.

Thus clonal trees are most likely 100% the same or identical if also grafted to clonal rootstocks. Trees grafted on different rootstocks are therefore not 100% the same, even if the DNA of the scion is 100% the same as the parent.

Another thought: When a scion variety is grafted onto a trifoliate rootstock, the grafted scion acquires certain characteristics form the trifoliate rootstock. Then when budwood is taken from the trifoliate grafted tree, and is grated onto a sour orange root stock, the new (second) scion, now has acquired some sour orange and trifoliate characteristics. This can go on and on, and on, each time the next generation scion is adding new characteristics from all the various rootstocks. After multiple graftings onto different varieties of rootstocks, and multiple added characteristics, does the last tree still produce EXACTLY the same variety of fruit, as the original mother tree did? (Close does not count) The DNA is moving down the line, but so are many other things, and there is a "changed" tree each time. This is what Jim is asking. - Millet

How is the DNA plus tree affected in cocktail trees (fruit salad trees)? I understand the rootstock affects some of the characteristics of the tree and make for the better tree. Does multi grafted trees affect each other even more? Or is it primarily roots affecting the branches and not branches affecting other branches.

Excluding bridge multi-rootstock grafts.

Millet I just want to be clear. You are saying that scion from a tree that is on trifoliate rootstock keeps some characteristics of that pairing to the next rootstock scion pairing? Or is that the question.

By joereal at 2008-10-23

Inoculum*
Tsn-RNA IIa (Enhances fruit size on Trifoliate orange rootstock)
Tsn-RNA IIIb (Reduces tree size and enhances fruit size on Trifoliate
orange)

Note: The effects on tree size and fruit production have been demonstrated only on trifoliate orange rootstocks. Experiments are currently in progress to determine if these beneficial effects on citrus performance can also be extended to other rootstock related to trifoliate.

gdbanks, I assume that it does retain some of the characteristics from each rootstock, but it is still a question. Keep in mind, a lot of the differences could be more intellectual differences than material differences. - Millet

tying it all together:

The previous example of Tsn-RNA modification of the plant grays out or blurs the line between phenotypic and genotypic expressions. It modifies the plant at the cellular level and forms a new plant whose characteristics can be passed on even vegetatively during budwood production, and perhaps genetically too (via mother's seed). Another example is the variegation of chimera type cultivars. Genetically, there could be just one gene that is different, perhaps just one base pair difference, but they could revert back and forth.

I haven't got the time to read or find out if such modifications like that of Tsn-RNA has lead to or will ultimately lead to modifications in DNA of the inocculated plant.

So the examples given out by Jim could be plausible. But the cheapest DNA test assay that I can find right now is about $15,000 per sample.

for humans though, the DNA genome assay, it costs only $5,000 per person.

Wow, I don't want to start or continue an argument here, but am I reading what I think I'm reading? The effect of a rootstock on a scion occurs ONLY while the two are attached. Soon (I would think within days) after they are disconnected, all of the rootstock influence would go away. Certainly in less time than it takes for a graft to heal or a cutting to root. The effect is due to the movement of various hormones and other non-genetic materials from rootstock to scion and the reverse. Those are simple chemicals that dissipate or are outgrown almost immediately. There are absolutely, positively, never, ever any retained characteristics. If there were, there would be all kinds of 'Valencia' trees -- the trifoliate/rough lemon/sour/swingle ones, etc. In fact, a particular clone (genotype) of 'Valencia' on Sour orange will always be the same, regardless of the countlessly many previous rootstocks in its lineage. If it's budded on sour now, it shows only the characteristics of a Val/SO graft.

Maybe I'm misunderstanding some of this conversation, and I do respect you guys, but the concept that there is any retention of such characteristics is completely in the face of all scientific evidence as well as our understanding of genetics, and against observation in hundreds of millions of trees. It just does not happen.

I should have continued above -- the Tsn-RNA work is interesting, and useful. But it is not, it seems to me, closely related to what is being discussed here -- the effect of a rootstock on a scion, and whether that is a permanent thing. Tsn-RNAs are a transmissible "disease" -- I don't like that word, really, but in the same sense that exocortis and xyloporosis viroids are "diseases" these are also viroids, which happen to give a desirable growth pattern in scions on Poncirus roots, without undesirable symptoms. In that sense, that they are infectious viroids, I use the term "disease." That's totally reasonable and scientifically supported. But it is not related to the effect of a rootstock on a scion, assuming neither is infected with any infectious agent, such as a viroid.

Dr. Manners has answered the question. The acquired characteristics a scion receives from a root stock remains as long as the scion is attached to the rootstock, and does not persist if additional grafts are preformed. - Millet

I google the above and budwood was supposed released several years ago inoculated with this stuff. Anyone heard of trees being sold commercially or to individuals identified as improved?

The way they are related is that we treat it as phenotypic effect on the scion. Both the rootstock's influence (while attached) and the Tsn-RNA effects are external to the plant's genotype, thus DNA are maintained per budwood generation propagation. The Tsn-RNA's effect are down to the cellular level and is passed on to subsequent budwoods, similar to disease spread, if the inocculation of the parent is successful.

I cannot make a generalization, however, giving rise to the possibilities that through time, after several generations of budwood propagation (ie, budwood from a graft which is a budwood from a previous graft and so on), that the DNA of the original parent remains pure. There could be some changes or mutations at some generation, depending upon the rootstock they were budded on (ie, different types of rootstocks have different rates of sport mutations), and the circumstances when they were grafted, and the continuous influences of various rootstocks and the environment at each generation. The very fact that we have now several types of Navel oranges as well as Valencia oranges originating from their own respective original parents. And most of these sport mutations come about without sexually assisted recombination, shows that these are happening through time at a slow rate.

Proof is that while the DNA may be very similar, but no longer 100% the same as the original parent. I currently have more than 20 types of Navels and more than 10 types of Valencias, and they are registered as distinct cultivars, at least in the UCR CCPP germplasm. As to what have caused these sport mutations through time, I could only speculate that different rootstocks may have played or contributed to the different sport mutations and I cannot rule it out.

And I would also add, that there are certain roles that the female material plays, aside from the DNA. The mitochondria for example seemed to evolve independently of DNA recombination, and is passed on by the female parent, and has significant roles in the phenotypic expressions. Not enough data but worthwhile looking into. Though it may seem unrelated, I have just a hunch that they might be. These are some of the findings, IIRC, that were presented by my colleagues more than 10 years ago in graduate school. Thus I love the disparate opinions, contradictory or not, both old and new evidences presented, to try to see if we can reconcile them under a better model of our evolving knowledge.