A connection between F2 fruit size & seed locules in F1 fruit?

[dfollett]

I’ve noticed something as I have been saving seed from different F1 crosses I grew out this summer. All the F1s I’m referring to are crosses between a micro multiflora that produces cherry-size fruit and various large-fruited indeterminate varieties. All the cherry-size fruit produced by the mama are typical cherry tomatoes with two seed locules in each fruit. The papas of the crosses are larger fruited indeterminates with numerous seed locules in each fruit.

I always assumed fruits from an F1 should be consistent (but then, I am an amateur with not a lot of knowledge about tomato genetics). As I’ve been saving seed, I’ve noticed that in some – but not all – of the F1s of the crosses the fruit from a single plant have varying numbers of seed locules. In some it is either 2 or 3 locules. In others, it is 2, 3 or 4, and in one case fruits with 2, 3, 4 or 5 locules from the same plant. One cross had nothing with 2 locules and everything had either 3 or 4 locules.

There was not a strong correlation between the fruit size and the number of seed locules. Perhaps on average, those with more locules were larger than those with fewer, but I certainly couldn’t guess before cutting into them which would have which. On one plant, the largest single fruit I harvested had two locules while the majority had three and more had four than had two.

Now to my question (I tend to ramble): When I grow out the F2s, is there any expectation of larger fruit on plants grown from seed out of fruits that had more locules than those that had only two like the typical cherry? What about fruit from seed of the 5-locule fruit versus that from the 2-locule fruit from the same F1 plant? Or, will all the fruit have the same potential regardless of the number of locules in the F1 fruit?

I kept the seed separate based on the number of locules and am wondering if it was a waste of effort. I'll have an idea a year from now as I grow out some F2, but I'd be interested in the insights of those of you who might know the answer. Is there is a likelihood of getting to larger fruit at F2 and beyond more quickly by focusing on seed from the fruits with more locules?

Thanks in advance for any insights.

[crmauch]

Originally Posted by dfollett

I always assumed fruits from an F1 should be consistent (but then, I am an amateur with not a lot of knowledge about tomato genetics). As I’ve been saving seed, I’ve noticed that in some – but not all – of the F1s of the crosses the fruit from a single plant have varying numbers of seed locules. In some it is either 2 or 3 locules. In others, it is 2, 3 or 4, and in one case fruits with 2, 3, 4 or 5 locules from the same plant. One cross had nothing with 2 locules and everything had either 3 or 4 locules.

There was not a strong correlation between the fruit size and the number of seed locules. Perhaps on average, those with more locules were larger than those with fewer, but I certainly couldn’t guess before cutting into them which would have which. On one plant, the largest single fruit I harvested had two locules while the majority had three and more had four than had two.

I read once back at the turn of the century, tomato breeders tried to progress their breeding programs by choosing a superior fruit. They made no real progress until they started making their selection for breeding on the whole plant (i.e. if the plant has one smooth tomato and the others ridged, the smooth tomato is not going to pass on different genes than the ridged ones.)

Originally Posted by dfollett

Now to my question (I tend to ramble): When I grow out the F2s, is there any expectation of larger fruit on plants grown from seed out of fruits that had more locules than those that had only two like the typical cherry? What about fruit from seed of the 5-locule fruit versus that from the 2-locule fruit from the same F1 plant? Or, will all the fruit have the same potential regardless of the number of locules in the F1 fruit?

I kept the seed separate based on the number of locules and am wondering if it was a waste of effort. I'll have an idea a year from now as I grow out some F2, but I'd be interested in the insights of those of you who might know the answer. Is there is a likelihood of getting to larger fruit at F2 and beyond more quickly by focusing on seed from the fruits with more locules?

I don't believe saving seed by locules will make a difference. Now if you have a plant that consistently has more locules on average than a different plant, that is something to select on.

[dfollett]

Originally Posted by crmauch

I read once back at the turn of the century, tomato breeders tried to progress their breeding programs by choosing a superior fruit. They made no real progress until they started making their selection for breeding on the whole plant (i.e. if the plant has one smooth tomato and the others ridged, the smooth tomato is not going to pass on different genes than the ridged ones.)



I don't believe saving seed by locules will make a difference. Now if you have a plant that consistently has more locules on average than a different plant, that is something to select on.

That is the same notion I have. However, shouldn't the fruit from an F1 all be the same? In most of the crosses I have, one or both of the parents are themselves not stable. In that case, seeds from different F1s will have different potential but all seeds from any given F1 will have the same potential - correct????

Perhaps the number of locules is more environmental than genetic. If that is the case, the seeds from the different fruits all have the same potential.

I searched my memory and on Tville and found that I had asked a similar question in a different thread and Bower answered saying basically the same thing. Thanks Bower (if I didn't thank you before).......

[crmauch]

Originally Posted by dfollett

That is the same notion I have. However, shouldn't the fruit from an F1 all be the same? In most of the crosses I have, one or both of the parents are themselves not stable. In that case, seeds from different F1s will have different potential but all seeds from any given F1 will have the same potential - correct????

If the parents are not stable then definitely different F1s may have different potential, but in general all seeds of a given F1 will have the same potential.*

Originally Posted by dfollett

Perhaps the number of locules is more environmental than genetic. If that is the case, the seeds from the different fruits all have the same potential.

That's what I believe. Now I think there are (on some of the smallest cherries) where the plant never has more than 2 locules, but on a lot of cherries 2 to 3 is common. I think this means the plant has a 'weak' active lc gene, but that would be in all the fruit/genetics of that plant.

*The only thing that *might* be exception is if a branch formed on a plant that all the tomatoes on that branch were different from the main plant. In that case, the changed genetics "might" be able to be passed on to its progeny. Plants have 3 layers of meristem tissue, and if the mutation is not in the layer from where flowers are formed, the mutation is not passible via breeding [I'm assuming a lot of this from reading about apples which are grown in vast quantities of clones and occasionally a favorable mutation is found which is then propagated into new orchards.]

My caveat: I'm only an enthusiastic amateur. Anything I said here might be wrong.

[dfollett]

Originally Posted by crmauch

If the parents are not stable then definitely different F1s may have different potential, but in general all seeds of a given F1 will have the same potential.*


That's what I believe. Now I think there are (on some of the smallest cherries) where the plant never has more than 2 locules, but on a lot of cherries 2 to 3 is common. I think this means the plant has a 'weak' active lc gene, but that would be in all the fruit/genetics of that plant.

*The only thing that *might* be exception is if a branch formed on a plant that all the tomatoes on that branch were different from the main plant. In that case, the changed genetics "might" be able to be passed on to its progeny. Plants have 3 layers of meristem tissue, and if the mutation is not in the layer from where flowers are formed, the mutation is not passible via breeding [I'm assuming a lot of this from reading about apples which are grown in vast quantities of clones and occasionally a favorable mutation is found which is then propagated into new orchards.]

My caveat: I'm only an enthusiastic amateur. Anything I said here might be wrong.

Thanks for confirming my thoughts. I probably wasted effort keeping separate the seeds based on number of locules. Since I did, I'll probably run at least one experiment comparing fruit size from 2-locule fruit vs. fruit from 4 or 5-locule fruit. At least then I won't feel like I totally wasted the effort and it will give me confirmation of the theory.

You are obviously ahead of me in your knowledge of plant breeding. Thanks for the comments.

[crmauch]

Originally Posted by dfollett

You are obviously ahead of me in your knowledge of plant breeding. Thanks for the comments.

You have done far more crossing than me of tomatoes and look to be successful.

My knowledge is mostly from books. I've read most of the amateur books and
have attempted some of the professional ones, but sometimes get lost in jargon
in those.

I have tried breeding a number of things, and none have resulted in anything.

Peas: wanted to breed a purple snap pea:
Got to the F2 and was growing them out when a deer decided to enjoy them.
There are now both yellow and purple snap peas available in catalogs.
Learned: Save back a number of seeds in case you have a disaster

Passionflower: wanted to breed a hardy edible passionflower:
Maypops (the hardy passiflora are 'edible', but don't taste very good
(IMHO) and there are edible, good tasting passifloras, but they're not nearly
as hardy. Could not find enough variation In the fruit of the hardy species
to attempt anything useful & my 1 successful cross between a hybrid and the
hardy species had an 9 seeds that I could not get to sprout (passiflora seeds
can be difficult to sprout and 'hybrid' seed can be worse) and have a weird
flower thing going (some flowers are male/female, some are male (female
parts withered) and others are effectively male [all on the same plant].
The plants also spread underground by roots.
Learned: Hybrid species add tremendous levels of complication. Starting
from a 'wild' species can be very difficult.

Roses: wanted to breed low-spray, but multi-petalloid flowers:
Did a lot of crosses, never got anything particularly interesting. Most of my
'breeding' stock got wiped out by Rose Rosette Disease (RRD). The former
rose bed is now a miniature forest.
Learned: Disease can wipe you out.

[bower]

hi dfollett, just saw this thread.

We had some discussion about the locule genes, lc and fas, in the Karma project thread earlier this year. It is pretty mystifying to me, especially when you throw other shape and size genes into the mix, so don't count on me for an authoritative answer... still blundering my way through it. Iirc I found some information during the Karma discussion that was contrary to what i thought or concluded before. This is what I'm thinking now:
- cherry or wild type fruit can have 2-3 locules, not only two. I have seen 3 in a longer fruit with the Sun gene involved.
- 3-4 locules (or is it 3-5?) indicate the lc locule number gene is present. I believe it is incomplete dominant, so it does show up in F1 crosses involving a cherry.
- I am not sure how fas/- without lc would affect F1 locule number but iirc the diagram, 6 locules would be fas/fas without lc.
- None of the diagrams showed fas/- lc/- heterozygous conditions so... darkness in that corner.
- personally, if I see more locules I do save them separately and pursue that as an indicator of the larger fruit. But in my case, I have seen these in multiparent crosses ie unstable varieties crossed. I don't think I've seen these different locule numbers in a cross of two stable vars.
Some reasoning/ "thought experiment" :
- fas plus lc together make the big beefs ( plus numerous fruit size qtls). So it stands to reason that the stable beefs in your F1 crosses had both fas/fas and lc/lc
This means that all your F1's would have fas/- and lc/- present. And if both parents are completely stable, all of the F1s must be genetically identical.
If so, then the expression of more locules must be purely environmental...

What are the other possibilities?
Is it possible that one or both parents were not completely homozygous?
Could there be other genes that affect the expression of locule number from fas and lc?
Given that these possibilities do exist, it is worthwhile IMO to compare the progeny of the F1 with more locules to those without.
If I were looking for larger fruit, I would always save seed from the more loculed plant where I saw the genes expressed most often, just to hedge bets on the uncertainties/unknowns.

[Nan_PA_6b]

DF, do you have any fruit on the F2's yet?

Nan

[KarenO]

To further muddy the waters there are many full size large Roma style tomatoes with two locules.
Some of the Karma cherry segregants have had multiple small Locules like a beefsteak. I have kept them separate as next gen of those tend to be bigger than cherry, not full beefsteak size but say 2-3 oz saladettes. I have seeds from them and a couple were fantastic in flavour so once the basic Karma cherry line is stable I may pursue a couple of the promising ones. I have a feeling that they could get bigger, likely full size beefsteaks through selection if that’s what is selected for but smaller/ earlier would be better from that cross for my goals.
If bigger fruit is what I wanted I would select the multi Locule to save seed from and vice versa, keep selecting from 2-3 Locule fruits to maintain the cherry. I get mega blooms in the karmas as well ( weird in a cherry) so I avoid saving seed from faciated fruits as well.
KarenO

[bower]

How cool is that, KarenO.
I'm seeing the same kind of 'anomalies' as well - larger fruit with 2 locules and smaller fruit with more. It is certainly worth saving seed separately as there are obviously other genes involved in fruit size at play. I would see both of those types as being especially useful for breeding (taste and other desirable qualities being present of course). You could breed for extra large cherries using the 2 locule type, while the multilocule would save you generations of work (or numbers of growouts) if you wanted to cross that fruit with a larger one to scale up the fruit size.

BTW I paid more attention to locule number this year, partly on account of this thread that got me grinding those gears. Took pics and will post some data when the seasonal crazybusy is done. A lot of similar sized fruit with different locule numbers, you could easily let the outliers slip by without noticing if you weren't paying attention, but they really are the ones I want...

[dfollett]

Originally Posted by Nan_PA_6b

DF, do you have any fruit on the F2's yet?

Nan

Not far enough along yet.

[crmauch]

You all may know this, but when segregating, do it by plant, not by 'fruit'. What I mean is if a cherry tomato normally has 2 locules, but occasionally 3, selecting the fruit that has 3 locules, will not give you different genetics than the fruit that has 2. If you have multiple plants, and one consistently has more locules than another, then you can seed from that plant and hold it separate from the 2 locule plants.

You probably all knew this, but I thought it was worth pointing out.

[dfollett]

Originally Posted by crmauch

You all may know this, but when segregating, do it by plant, not by 'fruit'. What I mean is if a cherry tomato normally has 2 locules, but occasionally 3, selecting the fruit that has 3 locules, will not give you different genetics than the fruit that has 2. If you have multiple plants, and one consistently has more locules than another, then you can seed from that plant and hold it separate from the 2 locule plants.

You probably all knew this, but I thought it was worth pointing out.

That is the understanding I have - but not the answer I wanted to hear. I understand what you are saying about fruit from different F1 plants vs fruit from the same plant. I was specifically asking about fruit from the same plant.

However, when you have some fruit from the same plant that have 5 locules ( and 3 & 4 also) and others that have only two - and supposedly larger fruited plants have more locules - It really feels like there ought to be a difference in potential

I understand the science and the theory - but it still doesn't feel right.

Thanks for the response.

[bower]

Genetics should be identical in the same plant, whether fruit has 2 locules or 3.

[KarenO]

Except in the case of a sport or somatic mutation. For example one fruit on a plant that has a heart shape instead of the expected shape. Seed from that fruit might produce hearts (or it might just be a deformity or a misshapen one or weather related) but the only way to know is to grow it out but you have to find it first and recognize it. I think many, many go unnoticed.
I have no science to back this up but I also think that many of the “typical rules” that apply to stable OP varieties don’t necessarily apply to early especially widely segregating crosses. It seem logical to me that genetically unstable plants will be more likely to produce more natural sports and somatic mutations than genetically stable plants purely by the numbers of potential genetic combinations possible. There is a lot of just plain luck involved (good and bad) and the science of breeding is mostly just playing odds but there are wildcards too and if you look for them carefully you might just find them
I think as well, for faciated fruits, the deformed/ multiple stigmas and overall
larger blooms can increase the likelihood of cross pollination hence the advice not to save seeds from those tomatoes that result from mega blooms.
I still always save seeds for the next gen of my crosses from the best most desirable shaped and sized fruits. There are always many to choose from and you might as well choose the best. Same goes for BER, cracking, catfacing, zippering etc etc . Theoretically, you can save seeds from any of those fruits too but why would I.
The pics I included are if an F5 fruit that should have been the bicolour KARMA “apricot” cherry. It’s neither the cherry it should be nor is it the beefsteak of it’s great great great grand parentage yet but I do think if grown out over successive generations and selection was done purely for size this multi Locule saladette size fruit would likely become a good sized beefsteak.
KarenO