somatic mutation

[bejustice]

What is the reasoning behind 8 filial lines for stabilization if you are working with a somatic mutation found in open pollenated heirloom? The desired trait is present in the mutant, the mutant made viable seeds and the desired trait is in it's progeny. Other than selecting for more productive plants, what are some of the seed companies reasonings for requesting this from breeders? I know it can't be looked at like a cultivar because of reproduction, but it is a mutant. Do I need to do eight generations to stabilize a somatic mutation? If it depends, why?

[Tom Wagner]

There ought to be some definitions accepted by all of the readers here. First of all ..somatic and filial don't go together.



Mutations are changes in a genomic sequence


Somatic mutations can occur in any of the cells of the body except the germ cells, thus a change in the genetic structure that is neither inherited nor passed to offspring


Acquired (or somatic) mutations occur in the DNA of individual cells at some time during a plant’s life. These changes can be caused by environmental factors such as ultraviolet radiation from the sun, or can occur if a mistake is made as DNA copies itself during cell division.


Again....Mutation is a change in a DNA sequence. Mutations can result from DNA copying mistakes made during cell division.......


Micro mutation as in a mutagenic event or in a simple deletion, insertion, or substitution of a gene.


Also..... Macro mutation as in a deletion of a part of a chromosome, a duplication of a part of the same. Inversions of a chromosome, or subbing part of a chromosome for another, and translocation of an end of a chromosome


Filial: generations of progeny in a genetic breeding project. One cannot have generations of progeny in a somatic breeding project




I am of the belief that all sorts of minor and sometimes, major mutations occur in segregating progenies, with all kinds of whole chromosomes from different parental backgrounds floating around in the production of ovules and pollen...the very imbalance of dissimilar chromosomes fosters the micro and macro mutations along with the simple re-assorting of the genetic material into alike alleles which increases with each filial level....theoretically. True breeding OP lines have less instability in the meiotic levels and micro/macro mutations have fewer opportunities.



True genetic mutations (deletion, insertion, or substitution) happening any time in the filial route to true breeding families of seed just makes sense and that one may wish to follow the filial levels out up to 8 generations to make sure the simple segregation and mutation fitness meld together as one. I base many of my true breeding lines as fixed if the important recessive genes are there. I do this quite often at the F-2/F-3 filials and the rest of the filials up to F-8 is just finesse. I never can be sure of anything...and trying to say exactly what is going on is mostly conjecture.



Bottom Line:
Somatic mutations cannot be kept going outside of cuttings or grafts. If it reproduces with the trait in consideration then it was not somatic.

[bejustice]

This is what I have. This pink was found amongst 600 white cherry. The plant only made this type. I have never seen this color before. The few I ate were very sweet. I think it has potential, but I need some guidance. We are really excited about it.

Sweet treats sells well, it is marketed as pink, but it is more red than pink. Sweet treats is a great tomato, but I never would have bought 600 seeds if it was not marketed as pink.

[Heritage]

Originally Posted by Tom Wagner

Somatic mutations can occur in any of the cells of the body except the germ cells, thus a change in the genetic structure that is neither inherited nor passed to offspring

bejustice, this definition can be confusing when applied to tomatoes. To help clarify, imagine the following scenario:

You have a tomato plant with red fruit. A somatic mutation creates one branch with yellow fruit.

Now, if you save seeds from one of the red fruit, they will NOT produce plants the same as the parent - i.e., with all red fruit except for one branch of yellow fruit. (the yellow-fruited branch is not inherited) However, if you save seeds from one of the yellow fruit (a point beyond the somatic mutation) all of the grow outs will produce only yellow fruit. So, technically, the yellow fruit is not inherited from the source (parent) but IS inherited if seeds are saved from a growth point beyond the mutation point.

In your case, if an entire plant produced the original pink fruit (shown in your photo) then it is most likely a crossed seed, or a mutation in the seed, and not a somatic mutation (it would have to mutate at, or near, the base of the plant to be a somatic mutation). However, if only one branch produced the pink fruit then it is a somatic mutation and seeds from the pink fruit will produce plants with all pink fruit. I am only personally familiar with one other somatic mutation: Casino -> Casino Chips, and I don't think the form/color has changed since the original mutation. I don't know if this is true for all somatic mutations in tomatoes.

At any rate, you should grow it out to check for stability. Also, you might start another thread to ask if anyone is aware of this mutation occurring previously - you don't want to rename something that is already available!. Carolyn, or one of the other experts will know and chime in. Congratulations on your find, and good luck!

Steve

[carolyn137]

Steve, I'm with you on your explanation and here's a few more somatic mutations I know of other than the Casino (large fruited red ) to Casino Chips, one branch had cherry tomatoes. Perfectly stable as those here who have grown it already know,including me.

Yellow Riesentraube;ONE yellow fruit on a plant with all normal red fruits and the yellow is perfectly stable/

And two I saw early in my so called tomato career but didn't save seeds.

Green Gage, a pre-1800 variety that has yellow fruits, one branch had all red fruits.And in doing some Googling I found that way back there were both red fruited and yellow fruited Green Gage versions.

Dix Doight de Naples ( 10 fingers of Naples), fruits are red and kind of short stubby finger looking, if you will,and one branch had red fruits, but of an entirely diffent shape.

Maybe I can think of other examples, maybe not.

Carolyn

[ChrisK]

Agree with this explanation. Was afraid Tom's would confuse some but didn't have time to post a followup.

My one quibble is that you say it's not inherited from the parent (depends on what you call a parent) But your example is pretty clear...save the yellow fruit.

Originally Posted by Heritage

bejustice, this definition can be confusing when applied to tomatoes. To help clarify, imagine the following scenario:

You have a tomato plant with red fruit. A somatic mutation creates one branch with yellow fruit.

Now, if you save seeds from one of the red fruit, they will NOT produce plants the same as the parent - i.e., with all red fruit except for one branch of yellow fruit. (the yellow-fruited branch is not inherited) However, if you save seeds from one of the yellow fruit (a point beyond the somatic mutation) all of the grow outs will produce only yellow fruit. So, technically, the yellow fruit is not inherited from the source (parent) but IS inherited if seeds are saved from a growth point beyond the mutation point.

In your case, if an entire plant produced the original pink fruit (shown in your photo) then it is most likely a crossed seed, or a mutation in the seed, and not a somatic mutation (it would have to mutate at, or near, the base of the plant to be a somatic mutation). However, if only one branch produced the pink fruit then it is a somatic mutation and seeds from the pink fruit will produce plants with all pink fruit. I am only personally familiar with one other somatic mutation: Casino -> Casino Chips, and I don't think the form/color has changed since the original mutation. I don't know if this is true for all somatic mutations in tomatoes.

At any rate, you should grow it out to check for stability. Also, you might start another thread to ask if anyone is aware of this mutation occurring previously - you don't want to rename something that is already available!. Carolyn, or one of the other experts will know and chime in. Congratulations on your find, and good luck!

Steve

[bejustice]

Thanks all, we are really excited about it. We build mixed pints. All the varieties we use are really special to us. We put a lot of effort into building the best ones we can, knowing they make a lot of people happy. Breeders make it possible.

A recent high school grad found the white cherry producing the pink cherries, and we are really proud of his efforts. We would like for this chance find to become a learning vehicle as he starts his college career. The schools have done a good job, he is speaking spanish, shows an interest in biological sciences and is not afraid to work. We want to reward and inspire with this tomato.

[carolyn137]

Originally Posted by bejustice

Thanks all, we are really excited about it. We build mixed pints. All the varieties we use are really special to us. We put a lot of effort into building the best ones we can, knowing they make a lot of people happy. Breeders make it possible.

A recent high school grad found the white cherry producing the pink cherries, and we are really proud of his efforts. We would like for this chance find to become a learning vehicle as he starts his college career. The schools have done a good job, he is speaking spanish, shows an interest in biological sciences and is not afraid to work. We want to reward and inspire with this tomato.

Ijust wanted to mention that the variety Dr.Carolyn is an ivory colored cherry and someone who bought seeds for it from SESE got a pink fruited plant and sent me seeds and he named it Dr.Carolyn Pink.

Some plants had pink fruits the size of the parent and some plants had pink fruits larger than the Dr.Carolyn cherries.

Carolyn

[Redbaron]

Originally Posted by bejustice

What is the reasoning behind 8 filial lines for stabilization if you are working with a somatic mutation found in open pollenated heirloom? The desired trait is present in the mutant, the mutant made viable seeds and the desired trait is in it's progeny. Other than selecting for more productive plants, what are some of the seed companies reasonings for requesting this from breeders? I know it can't be looked at like a cultivar because of reproduction, but it is a mutant. Do I need to do eight generations to stabilize a somatic mutation? If it depends, why?

I have to go with Tom on this one. Just because a somatic mutation caused a trait like pink fruit doesn't necessarily mean growing out that pink fruit will get you all pinks. Genetic material is still controlled by 2 genes. So even if the mutation is inherited (most somatic mutations are not passed at all) you will still have the standard AA Aa Aa aa result from those seeds.

The advantage of a mutation is that if it is passable (very very very rare for somatic mutations), the rest of the genetics are likely mostly Homozygous (identical alleles for a single trait), but that particular trait's alleles are still likely to be Heterozygous.

Now if it happens that the mutation is recessive, that makes it easy. Take that aa and you have a new cultivar completely stable after just one generation. But if the somatic mutation is dominant, then you won't be sure if it is an AA or an Aa and it won't be stable.

Far more likely with a somatic mutation is that it doesn't effect the seeds at all. It is likely to be an ancestral gene that is activated by an outside influence and will go right back to being dormant in following generations, if it is passed at all. I have read that for unknown reasons scientists don't quite understand yet, sometimes in plants a trait will pass one generation (and one generation only) and then go dormant from F2 on. It is suspected that is because it is in the RNA instead of the DNA. BUT that the RNA will trigger the dormant DNA. I can't be sure of that, the scientists are not even sure! But something in the plant cell machinery "fixes" it in the F1, so it shows up but doesn't pass to the F2. (so more properly called a phenotype that is passable to the next generation?)

What does that mean for bejustice's pink cherry in a field of whites? Well, it is likely the mutation (assuming it is not an accidental cross or simply a phenotype expression) happened LAST generation and he is actually seeing the F1 because it effected the whole plant. So

p= pink and w=white (recessive) P=pink W=white (dominant)

If the plant is a pp or PP, then the following generation will breed true.
If the plant is a Pw then 3/4's of the seeds will be pink and 1/4 white. And it will not breed true until stabilized.

p=pink and w= white and neither is dominant or recessive to each other.

Then likely what you have is a pw. Next generation will produce 1/4 pp pinks (likely regular darker pinks). 1/2 pw pinks (pale like in your photo). 1/4 ww whites.


So do you understand now why you have to do grow outs of successive generations and why companies request this from breeders?

Assuming the somatic mutation is passable at all, it could disappear forever after the F1. Even if it is passable to F2 onwards, it could be a Pw or pw and will not breed true. In some cases it will never be even possible to stabilize if it requires a pw to show. In that case you could only get it consistently from a hybrid between a pp and a ww parent. All of these possibilities mean one thing. You have to do the grow outs to prove it before a respectable company will sell it!

[bejustice]

Yes, thanks, getting clearer. The plant was weaker than the rest of the white cherries. They also started to ripen about two weeks after the regular white cherry. The plant seemed to be a little paler than the others.

[Doug9345]

I assume your are saving seed from it.

[carolyn137]

Originally Posted by Redbaron

I have to go with Tom on this one. Just because a somatic mutation caused a trait like pink fruit doesn't necessarily mean growing out that pink fruit will get you all pinks. Genetic material is still controlled by 2 genes. So even if the mutation is inherited (most somatic mutations are not passed at all) you will still have the standard AA Aa Aa aa result from those seeds.

The advantage of a mutation is that if it is passable (very very very rare for somatic mutations), the rest of the genetics are likely mostly Homozygous (identical alleles for a single trait), but that particular trait's alleles are still likely to be Heterozygous.

Now if it happens that the mutation is recessive, that makes it easy. Take that aa and you have a new cultivar completely stable after just one generation. But if the somatic mutation is dominant, then you won't be sure if it is an AA or an Aa and it won't be stable.

Far more likely with a somatic mutation is that it doesn't effect the seeds at all. It is likely to be an ancestral gene that is activated by an outside influence and will go right back to being dormant in following generations, if it is passed at all. I have read that for unknown reasons scientists don't quite understand yet, sometimes in plants a trait will pass one generation (and one generation only) and then go dormant from F2 on. It is suspected that is because it is in the RNA instead of the DNA. BUT that the RNA will trigger the dormant DNA. I can't be sure of that, the scientists are not even sure! But something in the plant cell machinery "fixes" it in the F1, so it shows up but doesn't pass to the F2. (so more properly called a phenotype that is passable to the next generation?)

What does that mean for bejustice's pink cherry in a field of whites? Well, it is likely the mutation (assuming it is not an accidental cross or simply a phenotype expression) happened LAST generation and he is actually seeing the F1 because it effected the whole plant. So

p= pink and w=white (recessive) P=pink W=white (dominant)

If the plant is a pp or PP, then the following generation will breed true.
If the plant is a Pw then 3/4's of the seeds will be pink and 1/4 white. And it will not breed true until stabilized.

p=pink and w= white and neither is dominant or recessive to each other.

Then likely what you have is a pw. Next generation will produce 1/4 pp pinks (likely regular darker pinks). 1/2 pw pinks (pale like in your photo). 1/4 ww whites.


So do you understand now why you have to do grow outs of successive generations and why companies request this from breeders?

Assuming the somatic mutation is passable at all, it could disappear forever after the F1. Even if it is passable to F2 onwards, it could be a Pw or pw and will not breed true. In some cases it will never be even possible to stabilize if it requires a pw to show. In that case you could only get it consistently from a hybrid between a pp and a ww parent. All of these possibilities mean one thing. You have to do the grow outs to prove it before a respectable company will sell it!

By definition somatic mutations occur in the soma, Greek for body, of the DNA of the cells, and are not associated with mutations in the seed DNA.

When I read this earlier you had used the example of a single yellow fruit, re Riesentraube, and saying that seeds from that fruit would not always give yellow fruits,

But they do, and Yellow Riesentraube has been known fo rmany years. Tania didn't have any info for it, so I looked in my SSE YEarbooks and it was first listed in 2000 and remains stable to today.

Casino Chips via the variety Casino has also remained stable as well. Same with Dr. Carolyn Pink.

So if it's a true somatic mutation, a single fruit can be changed, if the mutation is just involved with that one fruit, a single branch can be changed if the mutation is at the base of that branch, and, more difficult to ascertain is if it's a somatic mutation that changes all the fruits on a single plant.

A few years back we thought that a Yellow PRue had appeared, normal is red, but that turned out to be a fluke.

So, seed DNA and somatic DNA mutations are seperate and not related.

Carolyn, who was having a bit of a problem integrating your comments about somatic and seed DNA mutations, when you started talking about hybrids.

[Redbaron]

Originally Posted by carolyn137

By definition somatic mutations occur in the soma, Greek for body, of the DNA of the cells, and are not associated with mutations in the seed DNA.

When I read this earlier you had used the example of a single yellow fruit, re Riesentraube, and saying that seeds from that fruit would not always give yellow fruits,

But they do, and Yellow Riesentraube has been known fo rmany years. Tania didn't have any info for it, so I looked in my SSE YEarbooks and it was first listed in 2000 and remains stable to today.

Casino Chips via the variety Casino has also remained stable as well. Same with Dr. Carolyn Pink.

So if it's a true somatic mutation, a single fruit can be changed, if the mutation is just involved with that one fruit, a single branch can be changed if the mutation is at the base of that branch, and, more difficult to ascertain is if it's a somatic mutation that changes all the fruits on a single plant.

A few years back we thought that a Yellow PRue had appeared, normal is red, but that turned out to be a fluke.

So, seed DNA and somatic DNA mutations are seperate and not related.

Carolyn, who was having a bit of a problem integrating your comments about somatic and seed DNA mutations, when you started talking about hybrids.

That is correct and that's why I said extremely very very very rare. In fact in higher animals it is impossible. But in plants it is remotely possible.

A somatic mutation is not in the seed, but instead in one of the many other cells of a plant. In humans for example: A somatic mutation might cause a tumor or a cancer or even a harmless birthmark, but NEVER will that somatic mutation be passed on to the next generation. If it is not a mutation in a reproductive cell it can't be passed on genetically.

Plants are slightly different leaving the very remote possibility that a somatic mutation could be passed on in exceedingly rare instances. Tom said they wouldn't be passed at all, and he is mostly right. Somatic mutations do not pass on.

The rare exception in plants is when a somatic mutation, lets say in a branch cell, happens to be the cell that divides and produces a new bud which grows a sucker which produces new branches leaves etc.....and eventually a florescence. Then that somatic mutation COULD be passed on. In a human a cell with a somatic mutation on an arm can NEVER form a whole reproductive system. So like all higher animals, somatic mutations are never passed on. In plants a cell with a somatic mutation can in very rare circumstances form a functioning reproductive system and pass that somatic mutation on. Even in plants it is very rare.

A somatic mutation in a root for example would need to somehow form a new sprout from that root and not only that root, but from that particular cell in that root! Not going to happen often. More common would be that the somatic mutation will cause the cell to produce a molecule that is taken up by the sap to the rest (or just part) of the plant and can cause a molecular pathway to be activated, maybe even in very rare cases activate a dormant gene, but the mutation, not being in a seed cell, won't be passed on.

So lets take these exceedingly rare exceptions when the possibility of a somatic mutation could be passed on. The cell with the somatic mutation has beaten the odds and the mutation is both useful and the cell by chance happens to be in a growing tip that eventually produces a florescence. You still have the variables of the mutation being a single allele or gene or if it is one of the macro mutations as Tom described.

If it is a micro mutation then the same rules apply for stabilization as apply in traditional breeding work. (ie hybrids) If it is a macro mutation, it possibly could be stable right off (sometimes).

The point is that no matter what, a reputable company will want growouts to prove it. And that is the answer to the OP's question.

[bejustice]

I saved everyone I did not taste. I wish I had rooted a few cuttings. It was suggested to do so. The plant got pulled up with the rest. It has been a wet season.

[ChrisK]

bejustice,

Here's another reasonably good succinct explanation (followed by a lot of plant geekness!)

https://sites.google.com/site/dougla...omaticmutation