selction of plants

[charley]

ok im kina new at this i have a cross of earl faux and cherokee green f 1 seeds started .do i want to cross back to the earl faux so that i will have more potato leaf recessive plant to look for in the f2s and if so will it make it more difficult to find a green wr potato leaf.also i would like to know what i might expect to see from the cross also any other advice for plant selection what to look for .its to my under standing that if i get potato leaf and large tomatoes they are both recessive genes then it will have less segregation in the following grow outs?or is it that i would be more app not to lose a certian gene i want.i dont know this whole thing is confusing.help

[bower]

hi charley
So... your goal is to select a PL GWR from this cross.
I think we're talking about 2 different recessives for color, besides the potato leaf.

Green when ripe is gf/gf (green flesh) and y/y yellow flesh
While the pink is -/- for green flesh and R/R red flesh
Skin color I'm assuming doesn't matter. - some will segregate clear skinned like the pink (1/4).

Your F1 hybrid has this combination: RL/pl gf/- R/y
So it will appear regular leaf and red.

If you backcross the F1 to Earl's Faux you will have a one in two chance of potato leaf in the backcross F1 instead of 1 in 4, but you will have a much harder time to recover the double recessive color traits you wanted. The backcross would only have a 1/4 chance of a single gf allele (which you can't see until it's doubled) and likewise for the yellow flesh, as red and "not green" are dominant.

I think you're better off just gathering seeds from your F1 and then grow a dozen plants (or more) of your F2 and look for any combination of two recessives black (or gwr), yellow, potato leaf to select seed from if you don't get lucky and find all three. You can grow 6 or more of those plants the next generation looking for all three recessives, or you could make a cross between two of your F2's with complementary traits as soon as you identify them, or you could grow both parents on the side and backcross the F2 selection with the necessary parent to improve your chances of all three recessives in a minimum number of plants..

[charley]

wow this realy blows my mind.so if i find 2 plant both potato leaf and green w r if i cross them to each other i have a better chance of keeping the traits i want and the segregation will be kept to a minimum so i shouldnt need to grow as many plants?by the way thanks bower.

[bower]

This is true, Charley.. you would get less segregation and fewer plants needed to find recessives, if you used a parent with two or more of the recessive traits.
If you crossed your F1 to a PL GWR you would also reduce the number of plants to recover all three traits. Even a backcross to the Cherokee Green parent would put you closer, but harder to find the PL again, and you would need two generations to find out if the trait was kept or lost (because PL will only express when two alleles are present).
If you crossed Cherokee Green with a favorite PL black, or a PL yellow, that would take fewer plants than the pink cross. But if Earl's Faux has other traits you wanted to combine, why not continue with the cross you have, just be a little patient. these things take years anyway!

Did you have a limit on the number of F2 plants you can grow?
You need a half dozen plants for a good chance to select just one recessive. I've done that multiple times and only once failed to get the recessive with that number. On the other hand with only four plants, it is more likely you might not get the recessive. Then you might have to take another year and grow more F2.
Also, growing six plants I have several times got two recessives showing up - but not in the same plant. So for example, my Kitten Paws Pink F3 produced one of six PL plant, and another of the six was black fruited.
If I was looking for black and PL, I could have crossed those two F3's with a good chance of getting the traits together in the next generation - but the chances of that are BEST with crosses of F2's, we know that the recessive allele is hidden there in 2/3 of the dominant trait plants.

So I think it could be a lot of fun for you, to look for some traits you wanted in F2's and cross the F2 plants that had different recessives.
Six plants has been enough for one or two of two recessives to show up for me, maybe a few more would be better odds of finding all three of your traits..
There was a recent thread about this, and Fred made some helpful observations as well about finding your second recessive in the F3 generation - this is what I've seen as well, just with six plants per generation.
I also got lucky with ten F2 plants and got a double recessive I was looking for (black, determinate).
You never know your luck until you try..

[charley]

thanks very helpful im planning on growin 24 f2s this fall so i will have a better chance of getting what im looking for how many would i need to grow to get both potato leaf and gwr in the same plant in my f2s

[bower]

Technically the frequency of finding three recessives would be:
1/4 X 1/4 X 1/4 which is one in 64 plants.
Compare it is only 1/4 X 1/4 or one in 16 plants for two recessives. 24 plants would be certainly enough for this, but not close to the expected frequency for three.

Besides the workaround of looking for the third recessive in F3, or crossing two F2's that have the desired three traits between them, there is another option.
The handy thing about PL is that you'll know whether you have it at the seedling stage. Color traits you'll have to wait the months until you have ripe fruit, to find out what you got.
If you wanted to be certain to get all three traits in the F2, you could start four times 24 seeds, and only grow the PL ones, should be about 24 if you grow 96 seedlings.
The other option is also pretty good, to select the color traits in the F2, that is save lots of seeds from your GWR which you'll certainly get with 24 plants ( and maybe get more than one, so save seeds from all of them to make sure your PL allele is in the batch). Then the following season, start lots of seeds and once the leaves are out you'll know which ones are PL to keep.
The chances of finding the third recessive in F3 are actually quite good, because half the plants are expected to be heterozygous, that is RL/pl so they look RL but the pl allele is hidden there.
Choosing to select for color traits in F2 makes the most sense, since it's months of work to make the selection vs weeks to find a PL or not.
Also if you start ten F3 seedlings from one F2 and you don't find any PL, you can be pretty sure the allele isn't in that line so try another one.

I think you'll have an exciting year with 24 F2's from this cross. You'll have just about every color imaginable: yellow or white, pink or red, purple-black or brown-black, or green when ripe. I hope you post some pix of your favorites!

[charley]

i shure will post pic thanks bower.i have one more question you keep saying 3 recessive traits but im only aware of 2 the green w ripe the potato leaf whats the 3rd.i guess pink is recessive.what skin color would you select for

[Fusion_power]

Charlie, in the cross you mention, it is simple to do the selection needed. Grow the F1 plant from crossing a PL pink to a RL Gwr. Save the seed and then grow a boat load of F2's the next season. Keep only the PL seedlings. By growing only the PL F2's, you can pre-select and focus effort on finding the recessive color combination. Set out at least 32 of the PL plants and 1 or 2 of them should be a nice Gwr tomato. There will be a few other Gwr's among them, but not so good flavored so you can cull them.

[bower]

hi charley,

Green when ripe is a double recessive. There is yellow flesh, recessive to red. And there is "green flesh" also recessive, which makes a "black" with red flesh, and a "green when ripe" with yellow. You need yellow/yellow + gf/gf to get a gwr.

Yes, pink also has the recessive skin color (clear epidermis) but I don't think that matters, you can have a gwr with clear epi or yellow, just like with a black it can be pink-black or brown-black.

[WhippoorwillG]

I agree with KarenO. If you started 20 and none are PL, then something is amiss.

A PL crossed to an F1 that has a PL parent should throw PL plants at about 50%. There is almost no chance that you got zero out of 20.

There have been a lot of helpful responses, but if you aren't happy with your results, this is the best advice if you back up to the F2s, assuming you are still convinced the original cross was correctly labeled:

Originally Posted by Fusion_power

Charlie, in the cross you mention, it is simple to do the selection needed. Grow the F1 plant from crossing a PL pink to a RL Gwr. Save the seed and then grow a boat load of F2's the next season. Keep only the PL seedlings. By growing only the PL F2's, you can pre-select and focus effort on finding the recessive color combination. Set out at least 32 of the PL plants and 1 or 2 of them should be a nice Gwr tomato. There will be a few other Gwr's among them, but not so good flavored so you can cull them.

[charley]

Ok now im realy confused my f1 threw half gwr and half big orange tomatoes. What happened. I didnt think it would throw differant colors till the f2's.
All the gwr tomatoes are spitters.but the large orange is delicious so thats what i saved seeds from

[crmauch]

Charley,

I'm not sure why'd you get 1/2 gwr. Could your red tomato not been fully purebreeding?

Are you sure that your tomato there is fully ripe? I'm breeding for a better tasting beta carotene (one of the types of orange tomato where the orange is from beta carotene (like carrots) instead of red from lycopene) indeterminate paste (where the cross was beta X red paste tomatoes). My F1's appeared quite orange, which didn't quite make sense, and thought maybe something was wrong. However thought the fruit I picked was ripe, later in the season some of the tomatoes were left on the vine longer (and perhaps later season cooler temps?) the tomatoes got "fully" ripe and got a red blush which 'proved' they were hybrid F1s.

[charley]

They definitely do have a red blush but even the ones left on the vine longer we're still Orange Now i dont understand why.

[bower]

Charley that orange looks like a bicolor to me. It is a different color trait from the several types of orange. And there are no orange traits in the fruit you crossed... but I don't know, is Cherokee Green a GWR or a tricolor?

You were talking about doing a backcross, which one did you do? That would help to explain the results.

[crmauch]

Originally Posted by charley

They definitely do have a red blush but even the ones left on the vine longer we're still Orange Now i dont understand why.

Maybe someone with more knowledge of the GWR and "regular" red genes could jump in here as I'm not particularly familiar with the 'greenies' and their breeding.

My best guess (and that's all it is) is that you may have some sort of 'co-dominance'. For many genes it is either dominant or recessive, but sometimes for some genes each gene of the pairing expresses itself. (the example I've seen in talks about genetics is where a red flower and white flower are crossed and instead of red or white dominating, for certain species you'll get pink.)

Because from my limited experience, that tomato is not a r (R being Red-flesh), and various forms of r express less lycopene giving a range from orange to yellow to almost white (and possibly affected by modifier genes).

To me that tomato is trying to express red, and is being 'blocked' somehow.

Anyway, if you haven't seen it, you might want to look at this blog/article:

http://frogsleapfarm.blogspot.com/20...-color-in.html