Rootstocks can also increase vigor and yield. This is now a trend exploited by greenhouse growers who have started selling heirloom types (there is an article about this in the recent issue of the trade magazine "the Tomato Magazine").

Some varieties have roots which grow better than others, some poorer. The effects of poorer rootstocks can be seen in segregating crosses of regular tomatoes to wild (actually that likely can go the other way too).

The problem with studying roots should be apparent. The root studies I was familar with came out of Israel in the 90's. Most of these were hydroponic studies. One of the "issues" about these studies was similar to what you hear about studies in a test tube (in vitro) compared to "real world" in medicine. What happens in a test tube may not always be the same as what happens in the real world. So how roots grow and behave in hydroponic culture may be different than how they do in soil(s).

I do not know about tomato but some grafted rootstock unions can also transfer different carbohydrates and products manufactured in the roots up into the scion.

If you are interested in learning more google "Cary Rivard rootstock"

Bump!

Hoping someone who grafts tomatoes will see this and answer.

Did you google Cary Rivard?

mulio

Sorry, didn't mean to ignore your post, but I don't need to know about what rootstock to use or how to do it. I had looked up Rivard's research earlier, after another post was made here on GW discussing grafting and appreciated it. He mentions that the disease resistance of the rootstock is transferred to the scion, but it is not transferred to the seed of the scion, so that raises questions in my mind. He has great descriptions and illustrations on various sites about how to perform grafting.

But I want to know the botanical (chemical, hormonal, etc.) process involved, what characteristics the scion "adopts" from the rootstock beyond "disease resistance". How that works. He also mentioned that lateral branches that develop on the scion may produce inferior tomatoes and they should be removed. More questions.

If I've missed his answers to what I want to know, if you could post links, I'd be grateful!

I think I'm beginning to understand the process better and might even clear up some misconceptions that had vaguely arrived at the thought of a semi-hybrid scion tomato blended with the characteristics of the rootstock. It isn't that way at all!

It appears that the rootstock doesn't transfer anything to the scion but serves only as a kind of root-resister or root-filter against soil-borne diseases or other soil conditions that the scion may be vulnerable to but the rootstock has some resistance against. IOW, the benefit is that the rootstock has replaced the root uptake system of the scion, which may not have any defenses against some soil-borne diseases.

The scion's production and growth-habits are evidently dependent on its own genetics, not that of the rootstock, so nothing is transferred from the rootstock to the scion.

If you want to start a controversy go over to the hybridizing forum and bring this up there. There are a few who believe that grafting can influence genetics (I wont go into that or what i think about that). That is a controversial subject.

I'd just add again that grafting to another rootstock can have other benefits than just disease resistance.

Some plants grow bigger root masses and this can increase uptake of water, O2 and nutrients. This leads to a more vigorous scion than it would do on its own and that factor can increase yield and potentially even factors such as flavor or soluble solids.

The link below may or may not be helpful but you and others should find it interesting.

Here is a link that might be useful: PDF to Tomato Magazine which has a grafting article.

mulio

No, I don't want to get into a controversy about whether rootstocks affect the genetics of the scion! I'm willing to wait for the verified research.

I had said in one of the earlier posts that I wasn't interested in doing it myself, but I may change my mind and see what I can do next spring with some of the heirlooms I have after I see how they do this year. That is, IF I can get the principles under my belt and know what I'm doing!

Thanks for the link. I think I read that article before, so maybe it was given as a link in one of the earlier discussions.