Modern Hybrids with Four Parental Inputs?

[Chucker]

I see this statement quite often in posts talking about growing out F2s or dehybridizing. Supposedly modern hybrids will give much more diversity in the F2 generation because of the multiple parent lines.

I never really understand this. To create a marketable hybrid, it takes two homozygous parents, correct? So how does this work with four parents? I assume that from four parents, they create two new homozygous parents, and then produce the hybrid seed from those two "new" parents that they sell. But if that's the case, then they don't really have the genetic diversity of all four, but rather just from the two new parents. Am I missing something here?

[travis]

Here is a link to the release notice for Carolina Gold hybrid tomato.
http://www.ces.ncsu.edu/fletcher/pro...olina-Gold.pdf

On page one, you will read detailed descriptions of each of the two pure breeding parent lines that comprise the F1 hybrid cultivar.

You can see there is very little difference between the two parent lines, NC-1Y and NC-2Y. That is because they are derived basically from the same inputs. However, there are specific intentions for the use of each of the two parents, and together they achieve the intended purposes in the hybrid state.

On page two of the release notice, you will see the pedigrees of NC-1Y and NC-2Y.

As you can imagine, if you were to grow out F2 seeds taken from a Carolina Gold F1 hybrid tomato fruit, you will most likely get very similar results plant to plant in a F2 population. There may be some differences in fruit size, crack resistance, and a few other minor details, as you would expect from reading the specifics of the descriptions on page one.

[carolyn137]

Originally Posted by Chucker

I see this statement quite often in posts talking about growing out F2s or dehybridizing. Supposedly modern hybrids will give much more diversity in the F2 generation because of the multiple parent lines.

I never really understand this. To create a marketable hybrid, it takes two homozygous parents, correct? So how does this work with four parents? I assume that from four parents, they create two new homozygous parents, and then produce the hybrid seed from those two "new" parents that they sell. But if that's the case, then they don't really have the genetic diversity of all four, but rather just from the two new parents. Am I missing something here?

Too hot and humid tomight to go searching for the several threads where this is discussed,so I'll do the short version.

Yes, the earliest of hybrids had but two known parents but more modern hybrids can have up to four parental inputs in each of two breeding lines, so a total of 8 parental inputs.

Let's call it breedingline A. Start with an OP, it could be a known variety but is usually a special breeding accession. Breed into that a disease tolerance or two, take that one, and breed in uniform ripening, high solids content, for example, and then same thing for the 4th in line A.

Do thesame for line B, breeding this and that into the one before it, so at the end you have two lines and then you cross the two to create the F1 Hybrid,

A bit more complicated these days since before doing the last two in each line was done manually by removing the pollen bearing anthers on one line, but increasingly male steriles are created,which gets around that and you can directly place the chosen pollen directly on the stigma of the so called female.

Hope that helps.

Carolyn

[travis]

On the other hand, there are F1 hybrid tomatoes, which as you state in your post, have two pure breeding line parents which are significantly different from one another, and have totally unrelated, multiple parental inputs in complex pedigrees.

Here is the release notice for Mountain Magic, a "cocktail" tomato with two parents, one of which is a large globe and the other of which is a grape saladette tomato.
http://www.ces.ncsu.edu/fletcher/pro...tain-Magic.pdf

Here are the release notices for each of the two pure seed lines that comprise Mountain Magic F1 hybrid tomato:

NC2CELBR:
http://www.ces.ncsu.edu/fletcher/pro...R-NC2CELBR.pdf

NC-2 Grape:
http://www.ces.ncsu.edu/fletcher/pro...-NC2-Grape.pdf

At this link, you will find photos and descriptions of NCSU seed lines, including NC-2 Grape and NC2CELBR. As you can see, if you were to grow out a mess of F2 and F3 seeds from Mountain Magic, you would get results all over the map, including fruit sizes and shapes ranging from grape tomatoes to large globes, and plant habits from brachytic (birds nest sprawlers), thru short internode determinates, normal determinates, semi-determinates, short internode indeterminates, etc.

[Chucker]

Fantastic, great information, that helps a bunch!

Thanks Travis and Carolyn!

[frogsleap farm]

F1 hybrid seed will not give uniform progeny unless the two parents are true inbreds, homozygous at "all" loci. Those two inbred parents may trace to complex crosses of several breeding lines - but there are still only two parents in the F1 cross. As Travis points out, the more different the two parents are from one and other - the more segregation you will get in the F2.