Quote:
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.