Some questions about crosses

dfollett · January 11, 2015

I would appreciate some clarification/confirmation about a few details on what is to be expected on various aspects of crosses. I'll describe what I understand/assume and then point out what I am asking for clarification on:

Assumptions - Varieties A, B & C are all stable OP varieties.

First cross A x B - First generation is F1 and, depending on the different dominant & recessive genes involved, will be some mix of the two.

1 - My understanding is that the F1s will always be consistent. Any F1 seed from any fruit will have the same genetic potential. No need to grow out multiple F1s to realize the full potential of the cross in future generations - Correct?

2 - Segregation starts in the F2 generation. How much segregation there is and and how long it takes to stabilize will depend on the mix of various dominant and recessive genes in the parents. Like Forest Gump's box of chocolates, you never know what you're going to get - correct?

Second cross - (A x B) F1 x C

3 - The first generation of this cross is still referred to as F1 - correct?

I feel fairly confident up to this point. Now the question I wanted to get to:

4 - It seems to me that offspring from this cross will be like the box of chocolates from the get-go. Will the F1s a) show the same kind of variation as the F2s from above b) come more consistent but still with some variability, or c) will they be consistent like the A x B cross in whatever they produce?

5 - If the F1s are like the box of chocolates, will plant C contribute much to the differentiation (stated differently, will each variation of (A x B) react differently to the consistent contribution from C - or is that even a reasonable question?), or will the differentiation primarily be from plants A & B (as in the A x B F2s)?

If the F1s in the second cross are like the box of chocolates, it seems the right cross could give an almost unlimited possibility for differentiation. Or is there some determinable limited number of F1s that would need to be grown to exhaust the potential?

Thanks in advance for the clarification/confirmation.

Fred Hempel · January 11, 2015

1. Yes

2. In the F2 generation 1/2 of the genes become fixed (to the alleles of one parent or the other). 1/2 are still "heterozygous" (of course this is a simplification, because the parents will have the same alleles for some genes/traits)

But, there is alot of variability, and alot of potential for even more variability and combinations showing up in F3 and F4.

3. It is not really a classic F1, but these are often referred to as F1

4. You are right. All of the "hybrids" produced by the cross WILL NOT be genetically identical, so if you want to capture more diversity in subsequent generations you will need to harvest seed from multiple "F1" plants.

5. Correct. The variation you see (in the "F1") will be due to A and B, not C

You will get more potential variability in the situation you describe. To capture it, I would suggest saving from 5-10 "F1" plants, and then treating the "F2" like a normal F2 population (grow alot of plants to be able to see diverse combinations of traits.

dfollett · January 11, 2015

Thank you, Fred.

joseph · January 11, 2015

The definition of stable may vary from variety to variety... Some of the older heirloom varieties, and early commercial strains (for example Rutgers) have a lot of genetic variation inherent in the seed.

More modern non-hybrid varieties might have been created from single seed descent for 6 to 8 generations. They will have very little genetic diversity within them.

So the F1 generation from two so called "OP" lines may or may not be consistent from one to the other.

The F2 generation is not as much of a gamble as people make it out to be... Offspring tend to resemble their parents and grandparents. The traits of F2 plants tend to lie on a spectrum between the traits of the grandparents. Some looking closer to one grandparent or the other, or to be a blending of traits. There isn't much novelty that shows up... To use the Forest Gump analogy: If you start out with a box of chocolates that might have nuts in them or might have coconut, you will always get chocolates. Some might have nuts, some might have coconut, and some might have both, but don't expect to get any cream filled or cherry filled chocolates. And there won't be any taffy, or hard tack, or gummy bears.

The consistency of the (AXB) X C offspring may or may not have traits scattered all over the place, depending on how similar A and B are to each other... Again they will tend to carry a family resemblance, and have traits that are a blending of the traits of the "stable" ancestors. Because C is contributing half of the genetic material to this cross, and A or B are only contributing 1/4 of the genetic material, the offspring will tend to resemble C more than A or B. In the human world it would be like the difference between full-siblings and half-siblings. The family resemblances are still there, but modified in different ways.

For maximum diversity, do the cross as: (A x B) X (C x D)

**Tom Wagner** · January 12, 2015

I agree with Joseph that to get

Quote:

maximum diversity, do the cross as: (A x B) X (C x D)

I am making all sorts of ridiculous crosses to do this very thing such as seed I am sowing soon is to perform seven way crosses later on....

(Dwarf Shadow Boxing x Indigo Rose) X (Blueberry x Clackamas Blueberry)
and that will be crossed to...
(Yamali Blue x Dwarf Shadow Boxing) X (Strawberry Tiger x Primary Colors)

That is simpler to look at with those Alphabet Caps

{(A x B) x (C x D)} X {(E x A) X (F x G)} and each of the seedlings from this cross will be very different but some things will likely show up...blues, red flesh, slight stripes or even fully stripped, and perhaps remotely a dwarf since the Shadow Boxing is on both sides but no guarantee that it will show up...saving the seed to the F-2 level from many plants might though. The thing in common is blue tomato breeding work....as even Strawberry Tiger has Blue Tiger as a parent!

The variety Primary Colors is still segregating for some minor details and quite a few folks are playing around with it with different expressions since it was released three years ago. I have a single batch of 20,000 seed from one of my Primary Colors and if I would plant each seed, I would find variation of some degree. If I would cross a cross section of bulk pollen from the variable types of Primary Colors back to the 7 way cross seedlings I would get lots of diversity still.

One of the reasons I do so much mixing and mixing of hybrids on top of hybrids on top of hybrids is to break the poor flavor that so many blue tomatoes still possess from the original Indigo Rose. There is always the hope that multiple generations of crosses upon crosses fosters the chance of desirable translocations, deletions, additions, linkage, and/or other mutations which will result in happy accidents.

The seven way F-1 is akin to recombinant frequency breeding. The most common frequency occurrence if for blue stems and blue fruit. The next RF is for stripes and lesser RF for dwarfism. By growing a sizable number of F-1 plants I can select for blue stems, blue fruit and the possible dwarf vines. The stripes will be plentiful enough to conserve in the F-2 generation. Even if a dwar plant doesn't show up and can select from the four way crosses beforehand for the dwarf trait which I can see in the heterozygous form. If I have, say, ten plants of each four way cross I can easily pre-stage my breeding selection.

Fred Hempel · January 12, 2015

Tom,

How big does your backyard need to be, to grow out the proper "F2" population from your 7-way cross?

Fusion_power · January 12, 2015

Fred, I stood in his potato garden a couple of years ago and looked across the garden to the mountains. His garden is pretty big.

Just rounding up the numbers, you would need to grow around 500 million plants to capture every possible combination and recombination.

**Tom Wagner** · January 12, 2015

Quote:

How big does your backyard need to be, to grow out the proper "F2" population from your 7-way cross?

Thanks Fred, for implying that no person in their proper right mind would have a backyard big enough....

Darrel at least saw one of my plots which means I have to have dozens of so-called backyards just to stay afloat with all my selections. At least I my first level selection is done at the first transplanting from the starter trays. If I have 12 seedlings to choose from, be it F-! or F-2's etc, I transplant the 12 seedlings in a priority from one to 12 by desired characteristics and I have done well enough with that procedure to narrow down the number of plants I have to grow. I take some to the field, greenhouse, others to three gallon pots and many are left in in two or three inch pots to finish off. I could always use more places to plant but I often end up with one plant per cross or segregating line per garden.

I am sending out tomato seed of interesting crosses with only number identification to maintain some control of my lines. If the grower is offering seed back of F-2 seed of one plant per line...I am happy.

Here are some I am packing up this evening gong to the desert South West:

F-1 of Sunrise Bumblebee x Green Zebra
F-1 (Roman Candle x Blush) X (Blueberry x Clackamas Blueberry)
F-1 (Roman Candle x Blush) X (Muddy Waters x Hawaiian Blues)
F-2 (Harvard Square x F-5 Primary Colors)
F-1 (Yamali Blue x Helsing ★★★★★★★★ Blue) X (Mariana's Peace x Stupice)
F-1 (F-1 Indigo Kumquat x Borghese Vase Roman)
F-1 (Kaleidoscopic Jewel x Green Zebra
F-1 (11 way hybrid) X (Muddy Waters x Hawaiian Blues)
F-1 (Orange Fleshed Purple Smudge x Dwarf Shadow Boxing) X Green Zebra
F-1 (Amethyst Cream Cherry X (Strawberry Tiger x Primary Colors)
F-2 (Perfect Storm x Hahm's Gelbe)
F-1 (F-1 Sweet Baby Girl x Green Zebra)
F-1 (Muddy Waters x Hawaiian Blues) X Green Zebra
F-1 (F-2 Indigo Fireball X (Blueberry x Clackamas Blueberry)
F-1 Kellogg's Breakfast x Brandywine Suddths strain
F-1 (Black Zebra Cherry x Purple Calabash) X (Mariana's Peace x Stupice)
F-1 (Blueberry x Clackamas Blueberry) X F-1 Mountain Magic
F-1 (F-1 Red Delight X Green Zebra)
F-1 (Yamali Blue x Helsing ★★★★★★★★ Blue) X Chocolate Stripes
F-1 (Blueberry x Clackamas Blueberry) X Paul Robeson
F-1 (Flaming Burst x Blue Dawg) X (Blueberry x Clackamas Blueberry)
F-1 (Black Zebra Cherry x Purple Calabash) X Green Zebra
F-1 (Dancing with Smurfs x Ardwyna Paste) X (Muddy Waters x Hawaiian Blues)
F-1 (Dancing with Smurfs x Indigo Rose) X (Muddy Waters x Hawaiian Blues)
F-1 (Strawberry Tiger x Primary Colors) X (Muddy Waters x Hawaiian Blues)
F-1 (Muddy Waters x Hawaiian Blues) X F-1 Mountain Magic
F-2 (Strawberry Tiger x Primary Colors)
F-1 (Green Zebra x Paul Robeson)
F-1 (Striped Fahrenheit Blues X (Blueberry x Clackamas Blueberry)
F-1 (Striped Fahrenheit Blues X Borghese Vase Roman
F-1 (Yamali Blue x Helsing ★★★★★★★★ Blue) X (7 way hybrid x Yamali Blue)
F-1 (Flaming Burst x Blue Dawg) X Green Zebra
F-1 (Blueberry x Clackamas Blueberry) X Green Zebra
F-1 (Mariana's Peace x Stupice) X (Blueberry x Clackamas Blueberry
F-1 (Yamali Blue x Dwarf Shadow Boxing) X (Strawberry Tiger x Primary Colors)
F-1 (Dwarf Shadow Boxing x Indigo Rose( X (Blueberry x Clackamas Blueberry)
F-1 ( Roman Candle x Blush) X (Muddy Waters x Hawaiian Blues)
F-1 (Prime Beef Goliath x Paul Robeson)
F-1 (Dark Orange Muscat x Skykomish)
F-1 (Black Zebra Cherry x Blush)

The fella getting these seeds will not be able to share with you as he is getting only one seed per line. If you figure the man hours to start and grow the parent stock, make the crosses, harvest the fruit, extract the seed and pack it away...the man hours alone would be where no person could afford to buy the same sampling of tomatoes. And to think I have thousands of these kinds of crosses just sitting around.....

January 11, 2015	#1
dfollett Tomatovillian™ Join Date: Dec 2012 Location: Utah Posts: 693	Some questions about crosses I would appreciate some clarification/confirmation about a few details on what is to be expected on various aspects of crosses. I'll describe what I understand/assume and then point out what I am asking for clarification on: Assumptions - Varieties A, B & C are all stable OP varieties. First cross A x B - First generation is F1 and, depending on the different dominant & recessive genes involved, will be some mix of the two. 1 - My understanding is that the F1s will always be consistent. Any F1 seed from any fruit will have the same genetic potential. No need to grow out multiple F1s to realize the full potential of the cross in future generations - Correct? 2 - Segregation starts in the F2 generation. How much segregation there is and and how long it takes to stabilize will depend on the mix of various dominant and recessive genes in the parents. Like Forest Gump's box of chocolates, you never know what you're going to get - correct? Second cross - (A x B) F1 x C 3 - The first generation of this cross is still referred to as F1 - correct? I feel fairly confident up to this point. Now the question I wanted to get to: 4 - It seems to me that offspring from this cross will be like the box of chocolates from the get-go. Will the F1s a) show the same kind of variation as the F2s from above b) come more consistent but still with some variability, or c) will they be consistent like the A x B cross in whatever they produce? 5 - If the F1s are like the box of chocolates, will plant C contribute much to the differentiation (stated differently, will each variation of (A x B) react differently to the consistent contribution from C - or is that even a reasonable question?), or will the differentiation primarily be from plants A & B (as in the A x B F2s)? If the F1s in the second cross are like the box of chocolates, it seems the right cross could give an almost unlimited possibility for differentiation. Or is there some determinable limited number of F1s that would need to be grown to exhaust the potential? Thanks in advance for the clarification/confirmation.

January 12, 2015	#7
Fusion_power Tomatovillian™ Join Date: Feb 2006 Location: Alabama Posts: 2,250	Fred, I stood in his potato garden a couple of years ago and looked across the garden to the mountains. His garden is pretty big. Just rounding up the numbers, you would need to grow around 500 million plants to capture every possible combination and recombination. Last edited by Fusion_power; January 12, 2015 at 07:00 PM.

January 11, 2015	#2
Fred Hempel Tomatovillian™ Join Date: Dec 2010 Location: Sunol, CA Posts: 2,723	1. Yes 2. In the F2 generation 1/2 of the genes become fixed (to the alleles of one parent or the other). 1/2 are still "heterozygous" (of course this is a simplification, because the parents will have the same alleles for some genes/traits) But, there is alot of variability, and alot of potential for even more variability and combinations showing up in F3 and F4. 3. It is not really a classic F1, but these are often referred to as F1 4. You are right. All of the "hybrids" produced by the cross WILL NOT be genetically identical, so if you want to capture more diversity in subsequent generations you will need to harvest seed from multiple "F1" plants. 5. Correct. The variation you see (in the "F1") will be due to A and B, not C You will get more potential variability in the situation you describe. To capture it, I would suggest saving from 5-10 "F1" plants, and then treating the "F2" like a normal F2 population (grow alot of plants to be able to see diverse combinations of traits.

January 11, 2015	#4
joseph Tomatovillian™ Join Date: May 2013 Location: Cache Valley, N/E of The Great Salt Lake Posts: 1,244	The definition of stable may vary from variety to variety... Some of the older heirloom varieties, and early commercial strains (for example Rutgers) have a lot of genetic variation inherent in the seed. More modern non-hybrid varieties might have been created from single seed descent for 6 to 8 generations. They will have very little genetic diversity within them. So the F1 generation from two so called "OP" lines may or may not be consistent from one to the other. The F2 generation is not as much of a gamble as people make it out to be... Offspring tend to resemble their parents and grandparents. The traits of F2 plants tend to lie on a spectrum between the traits of the grandparents. Some looking closer to one grandparent or the other, or to be a blending of traits. There isn't much novelty that shows up... To use the Forest Gump analogy: If you start out with a box of chocolates that might have nuts in them or might have coconut, you will always get chocolates. Some might have nuts, some might have coconut, and some might have both, but don't expect to get any cream filled or cherry filled chocolates. And there won't be any taffy, or hard tack, or gummy bears. The consistency of the (AXB) X C offspring may or may not have traits scattered all over the place, depending on how similar A and B are to each other... Again they will tend to carry a family resemblance, and have traits that are a blending of the traits of the "stable" ancestors. Because C is contributing half of the genetic material to this cross, and A or B are only contributing 1/4 of the genetic material, the offspring will tend to resemble C more than A or B. In the human world it would be like the difference between full-siblings and half-siblings. The family resemblances are still there, but modified in different ways. For maximum diversity, do the cross as: (A x B) X (C x D)