Role mutations play in generating new varieties

[Doug9345]

A discussion started in this thread about all OP being hybrids once and it when on to discuss mutations here are the relavent posts

http://tomatoville.com/showthread.php?t=30879&page=5

Originally Posted by drew51

Are not all hybrids a cross between two or more OP's? They would have to be to produce a consistent F1. All OP/Heirloom were hybrids too! Still are in the true sense of the word. Many hybrids taste great. Sun Sugar, Jasper cherries are amazing. I see that many sell stable hybrids, as they tasted so good, it was worth the effort to stabilize the genes. Also the line between commercial and heirloom is age, which to me, means it tasted good enough to keep around, again all were hybrids at one point. Every single heirloom was a hybrid.

I can see some of the super resistant types might have a taste change, but those are needed as some growing areas have so many problems. it's great that one can at least grow something in those areas.

Originally Posted by carolyn137

Only the earliest of F1 hybrids have but two stable OP parents, ones like Ramapo, Better Boy, Big Boy, etc. More modern hybrids are constucted with two breeding lines and in each line there can be up to 4 different parental inputs, then the last one in each line is crossed with the other one, giving you the final F1 hybrid.

Not all OP heirlooms were hybrids at one point. That leaves out the important mechanism of mutation, which was a major force, especially when tomatoes were first evolving, and even now when random spontaneous mutations do occur from time to time, and that means both seed DNA ones as well as somatic mutations which occur in the cell of a plant.

Carolyn

Originally Posted by WhippoorwillG

This may take us on a tangent, so it may be more appropriate to move this to a new thread or the one referenced below to prevent muddying the waters in this thread.




I wanted to address this in the last op vs hybrid vs heirloom thread, but didn't want to take explanations to the Nth degree in an attempt to keep it basic. However, since you brought it up, I am very curious about any known non-hybrids that are passed around today outside of numerous small/medium fruited wild types.

In the above referenced thread, I made the blanket statement that all heirlooms were hybrids at one point. I had originally inserted a disclaimer about it being mostly true, outside of wild types and "land races," but deleted it for the sake of brevity (not a natural attribute of mine ) I did not intend to discount mutations, since we would be hard pressed to explore the genetic diversity of the tomato(or anything with genetic coding) and its relatives if there weren't mutations.

However, I do not consider a gene mutation alone to make a new non-hybrid variety. I am specifically speaking to traits such as PL vs. RL. If a hybrid is found/created that eventually mutates from a RL to a PL, or red to green fruit, it is still a product of a hybrid. Is it genetically different? Yes. But is it still a hybrid with respect to the ancestry? Yes.

My primary curiosity is: Are there any large fruited varieties still in cultivation today that are thought to be solely evolved from small green wild types? Large fruit is heavily a product of increased locule count, along with several other contributing factors, but I have not seen any referenced as ancient or passed down from antiquity. That's not to say they don't exist...I just haven't seen mention of them in the text I've read. Of course there are the numerous wild types, and selections made from wild populations, but all I am familiar with are between tiny and small, not slicing size.


As always, thanks to those that are willing to share their knowledge.

Originally Posted by carolyn137

I agree that this thread is not the place for this discussion, so I'll be brief.

Tomatoes from Chile and Peru, the wild types, evolved not from the green fruited ones, but from the red fruited one Solanum pimpinellfolium. This is known from many studies where restriction analysis of snips have confirmed that.

Each gene can have one or more alleles.

Right now I don't remember the gene designation for leaf form, as to PL and RL, I should remember so I'm going to claim Senior Citizen amnesia, but here's an example.

Let P be domininant

Let p be recessive

So one can have"

PP, homozygous dominant and RL

Pp, heterozygous and domininant, RL

pp, homozygous recessive and PL

If with Pp the p mutates, then the result is from Pp, RL to pp, and PL.

And for some tomato genes there are many alleles, alternative forms of a single gene.

There are other ways of going from RL to PL as well, that involve DNA events such as repeats, looping out, inversions, and genes can be altered in that way also.

(However, I do not consider a gene mutation alone to make a new non-hybrid variety. I am specifically speaking to traits such as PL vs. RL. If a hybrid is found/created that eventually mutates from a RL to a PL, or red to green fruit, it is still a product of a hybrid. Is it genetically different? Yes. But is it still a hybrid with respect to the ancestry? Yes.)

If the assumption is that a stable OP is homozygous for all genes, as it should be, then a mutation could change any particular trait to another phenotype.

I guess it's best that we agree to disagree on the evolution of tomatoes, starting with the currant tomato b'c the work of several scientists has shown that it was upsized due to mutation initially and initially from few locules to several.

No one knows for sure what happened in Mexico where they first showed up, but it's clear that the first ones taken from Mexico to Spain were yellow. Subsequently red ones also showed up in Italy, all by mutation.

Yes, it happens. Green Gage is a pre 1800 variety that I've grown and one year one branch had all red fruits while all other fruits on the plant were the normal yellow. That's called a somatic mutation where the mutation is in a plant cell, as opposed to a seed DNA mutation.

Yellow Riesentraube? A person found ONE yellow fruit on a plant with all other fruits being the normal red. Another somatic mutation.

Carolyn