Are cross pollinated seeds within one fruit identical?

I was teaching a seed saving class and got an observation from a student that stumped me.  He saved the seeds from one pumpkin fruit that had been cross pollinated by some other squash.  He then planted those seeds for the next few years.  The plants and fruit he got from that batch of seeds from a single fruit were widely varied.

It's probably a silly question when faced with his clear experience.  But just to check, is that how it should work out?  I guess I was thinking if one piece of pollen from one plant hit the pistil of another flower that the entire fruit would have the same hybrid seeds inside it.  Say half pumpkin, half zucchini.

Maybe my understanding is based on the assumption that to make a hybrid veggie plant they'd pollinate one set of flowers with another plant and get reliable F1 children from the cross.

If you and your partner had a baby. Would every single child be the same?

Nope,

If you had two inbred strains of squash and you very carefully taped a male and a female flower one from each shut before they opened and made the pollination yourself then taped them shut again you would get a uniform F1.

With the bees doing the work you should get variation. Some pollen from each variety available. What is more, say one or both of those squashes were hybrids. They would be segregating still, so the offspring would be wonderfully. What is more if more than two varieties were with the reach of bees, while pollen might have come from any of them.

So this year when I planted two landraces, a grex, and a hybrid into my Moschata patch I will almost certainly have fruits that could have been pollinated by one bee, but with pollen from as many as four widely divergent sources and within each of those four great variation should exist. Also my Mospermia patch was decently far away, but perhaps not impossibly far for a determined bee. Also it's possible a maximoss might have been lurking somewhere within a bees reach and maxima definitely were. What could happen? Well, probably some very lovely squash plants next year. The only mystery is what the fruits will look and taste like.

We know who's the mamma, but every seed could have a different daddy.

Each seed is a "baby" right? And, the fruit is like a womb. So if Zucchini Dad and Pumpkin Mom got together, and she had triplets in her womb/flower, those would all have different genetic DNA, right?

Each parent has 2 different alleles for each trait/gene, right? Sometimes, a parent is homorozygous for a trait--that means both alleles are the same. Like when you inherit blue eye genes from both your parents. And, if your spouse has blue eyes  with two blue eye traits, your kids will have blue eyes.

But, you could also have, say a parent with blue eyes and one with brown. Your eyes are brown, but you carry the recessive trait. You are heterozygous for that trait. You marry someone who also has brown eyes, but carries the blue eye trait. And then, "out of the blue" you have a blue eyed child! Those recessive traits managed to roll the proverbial dice and match up. It's a 1/4 chance for that.

I'm guessing most varieties of plants we buy in a catalog, especially if they are heirloom, are homozygous for ALL their traits. They don't have any sneaky recessive traits. Those are bread out. So, when they self pollinate or pollinate with another of their variety, their babies look exactly like them in every way. That's pretty inbred!

But, when Zucchini Dad and Pumpkin Mom get together, even though both of them are homorozygous, they both have vastly different traits from each other (like someone with tan skin and brown hair and brown eyes, matching up with someone with strawberry blond hair, freckles and blue eyes). So, you never quite know WHAT the offspring will be like. Each baby could be so different! And, most of them will carry sneaky recessive traits. And when they breed, all sorts of genetic dice will be rolled, and the kids will continue to look very different!

I guess I was thinking if one piece of pollen from one plant hit the pistil of another flower that the entire fruit would have the same hybrid seeds inside it.

With just one pollen grain, you'd generally get one seed.  Only.  Each seed has its own 'daddy'.

That's why some wild bees are such pollinators - they tend to roll in the flowers and get smothered in pollen so the next flower they land in gets a good mix of pollen hitting all the available slots.

Thanks for all the replies.  So even if only 7 pieces of pollen landed on the female flower, all 500 seeds in that fruit will contain a wild variety of combinations, partially from the 7 different fathers but also because the genetic diversity of even inbred squash lines becomes chaotic when they cross pollinate.

So to get a deliberate F1 hybrid (sun gold tomato?), how do they control it to get a reliable child?  Is it just because tomatoes are even more inbred and consistent?

Mike Jay wrote:

So to get a deliberate F1 hybrid (sun gold tomato?), how do they control it to get a reliable child?  Is it just because tomatoes are even more inbred and consistent?

For all 'typical' commercial F1 hybrids that I'm aware of, the mama and papa are highly inbred lines.  This way the F1 *can* be close to genetic similarity....and provides the reliable uniformity that most gardeners and large-scale ag producers prefer.  For some crops like beets, the crop is naturally outcrossing and it's not so easy to get uniform parental lines.  But they produce F1 seed essentially the same way.

Mike Jay wrote:Thanks for all the replies.  So even if only 7 pieces of pollen landed on the female flower, all 500 seeds in that fruit will contain a wild variety of combinations, partially from the 7 different fathers but also because the genetic diversity of even inbred squash lines becomes chaotic when they cross pollinate.

So to get a deliberate F1 hybrid (sun gold tomato?), how do they control it to get a reliable child?  Is it just because tomatoes are even more inbred and consistent?

It takes 500 pollen grains to get 500 seeds. In theory a bee might visit 500 different father plants and deposit a grain of pollen from each to get those 500 seeds. Most of the F1 diversity will come from the fathers. If the mother is inbred it will not segregate in the F1, and will be a tremendously stabilizing force. Segregation of both mothers and fathers happens in the F2.

As someone already said. To get a deliberate F1 hybrid you need an inbred mother and an inbred father. Then the F1 will be markedly uniform.

However the F2 of an F1 from two inbred parents will segregate wildly especially if both inbred grandparents were very different from one another. You can get landrace level diversity from such a cross in the F2.

I grew Hidatsa squash and Rio Lucio squash in 2016. In 2017 I planted all the seeds from a 2016 squash open pollinated. I got mostly F1 hybrids, but a few selfs. Only had a few plants in 2016. Had hundreds in 2017. The fruits were pretty uniform. In 2018 I had more segregation.

Thanks William!  So I've been mistakenly thinking that one piece of pollen is all it takes to make a squash full of seeds.  Would it make a squash with only one seed in it?  So to get 500 seeds you need 500 bits of pollen?  Kind of like why an underpollinated corn cob is missing a bunch of kernels.

One pollen grain produces exactly one seed. If 7 grains of pollen land on a flower, you can get at most  7 seeds. To get 500 seeds, at least 500 pollen grains need to land on the flower, and they can have as many different daddies as the bees have been visiting.

I don't think of plant breeding as chaos... Offspring tend to resemble their parents and grandparents. And the physical traits of offspring tend to be mid-way between their parents most of the time. There are a few alleles where the result is EITHER/OR, but mostly the physical traits end up being AND. I observe that blended families are not developing new traits, they are just experiencing minor variations on an age old theme. I don't find new poisons, or new kinds of root systems, or radical differences in growth habit... Just minor variations of the family's basic theme.

For example: in maxima squash, there are basically 3 colors pigments in the skin: White, green, or orange. Then there is a modifier that makes the color intense or pale. Then there is a gene for stripes. That's it. The color of the fruits are just some play on those three basic genes. Seems unified and consistent to me, not chaotic.

There are basically three shapes in maxima squash: round, banana, buttercup, or some blending of those three shapes.

Thanks Joseph!  I think I'm all squared away now.  Permies rocks!

Great topic.
I had never even thought to ask that question before.

Each stigma and style connect with separate ovaries in the flower. So each stigma/style/ovary can receive a different grain of pollen from different and unrelated "daddies" and develop into seeds that are unrelated on the "paternal" side of the equation. So the answer is no, cross pollinated seeds within one fruit are NOT identical.

For corn (Zea mays), the traits of the male parent are expressed in the pollinated kernel so there will be the risk of occasionally crunching on a hard or mealy kernel when eating a cob sweet corn grown nearby a patch of flint corn or popcorn. A similar problem will arise when growing popcorn next to other types of corn. There will be a risk of fewer kernels popping properly if the popcorn is pollinated from nearby a patch of another variety of corn.

I know squash are easy to cross in the family.
Sometimes you will plant 20 yellow squash seeds & one plant will be green or striped.

I do know that if you gather Red Dogwood seeds, that 20-30% will be white, they will not bloom for the first five years.
But it is the cheapest way to grow red dog woods.

Plants are weird.  No 2 seeds seem to produce the same plant as the parent.  Even if they look alike, analyzing the nutritional qualities of the seeds, for instance, will show they vary from each other.

Jerry Davis wrote:Plants are weird.  No 2 seeds seem to produce the same plant as the parent.  Even if they look alike, analyzing the nutritional qualities of the seeds, for instance, will show they vary from each other.

People are the same way.
Except for identical twins, we are all a little different.

One pollen grain produces exactly one seed. If 7 grains of pollen land on a flower, you can get at most  7 seeds. To get 500 seeds, at least 500 pollen grains need to land on the flower, and they can have as many different daddies as the bees have been visiting.

Does this mean that if I collected pollen from multiple different heirloom tomatoes and applied it to the same emasculated flower, the seeds in the resulting tomato would be a mix of all of them? As in, rather than doing a bunch of different 1-1 crosses, I could just have one big tomato bukkake and have, most likely, a few seeds of each cross within one fruit.
Am I correct?

Jeremiah Squingelli wrote:

One pollen grain produces exactly one seed. If 7 grains of pollen land on a flower, you can get at most  7 seeds. To get 500 seeds, at least 500 pollen grains need to land on the flower, and they can have as many different daddies as the bees have been visiting.

Does this mean that if I collected pollen from multiple different heirloom tomatoes and applied it to the same emasculated flower, the seeds in the resulting tomato would be a mix of all of them? As in, rather than doing a bunch of different 1-1 crosses, I could just have one big tomato bukkake and have, most likely, a few seeds of each cross within one fruit.
Am I correct?

The biology teacher at the school I teach at says YES.
He says it can be a bit more complicated in some cases.
But, I won't give you his extended answer.
He can be rather verbose.

Huh, that's incredibly interesting and useful.
I'll give a whorl with some tomatoes I'm ordering and get back to y'all if I get anything interesting out of it

Yeah I didn't read super carefully so sorry if someone already said so, but each seed is formed from a different egg cell, and is fertilized by a single sperm cell from pollen. So within a single fruit each seed will be the equivalent of siblings or half siblings, depending. If the plant is self-pollinating there is less genetic variation than if the pollen comes from a different plant, or even multiple other plants. There is a LOT of genetic variation within single plant species.

I think that an interesting related question might be whether and how individual seeds can tell us about their parentage.

In some other threads, the xenia effect has been discussed, namely that individual seeds can express certain traits from the pollen donor.  Joseph Lofthouse here discussed how, in corn, there are four factors that can contribute to the color of the grain.  Two relevant parts are mother only (seed coat and sap), and two parts include father (the aleurone and the endosperm, which have the complete mother genome plus the copy of the father genome that was not included into the seed).  Thus, you can identify the occasional strange father.  

Would you be able to identify different squash seeds (by size or morphology, for instance) as coming from a different father?  How about beans (by color or shape)?  Or, is corn (or grains generally) the exception and even other hybrid seeds will resemble the mother (or at least be set by the mother's genome) most of the time?

There are documented xenia effects in corn and squash seeds. They are due to subtle difference in seed size and morphology. Something better measured with instruments than by looking with the eyes.

In the first generation, the traits of offspring tend to fall mid-way between the traits of each parent, so you can often know who's the daddy. The grandchildren of a cross will often reveal even more about who was the original parent of the cross.

Just a note on plant pollination. Plants with endosperm and embryo are double pollinated. It takes two cells from the pollen grain and also I think the endosperm is triploid.

https://en.m.wikipedia.org/wiki/Double_fertilization

Now this is a bit different from what goes down in animalia and ocassional errors in the process result in interesting outcomes.

For instance sometime the endosperm might grow into a triploid plant.

Or sometimes each sperms cell might be contributed by a different pollen grain.

So because plants are rulebreakers one in a million pollinations or so goes haywire and rules get broken.

Thanks for the explanations.  In doing a little research I see that there are a few kinds of plants with xenia effects.  You might see it especially in inter-species crosses, but even between varieties that would readily cross it can show up.  Unfortunately, it doesn't seem like within a single cross between common bean varieties you can readily identify which individual beans, say, were going to result in a F1 hybrid just by looking at it (though inter-species crosses make it more likely that you'd notice).  I'm interested because I found some beans that were a different color than either of the ones I planted last year.  I suspect that it must have been a fluke hybrid that grew out.  We'll see if anything interesting appears this year!