Making cross with an unstable (F3) line...

[BoilerMan1812]

Your thoughts on using an F3 in a cross? I know this is not yet stable but assuming I identify a plant with the appropriate characteristics, would you advise that I use the plant in a cross?

Thanks in advance!!

[sirtanon]

It will give you variability, but that's not necessarily a bad thing. The genetic variability can actually result in lots of very cool segregates.

Having said that, there are tons of crosses that have been shared on here, including quite a few within the Dwarf Breeding Project, that have included F2 parents, and even F1's.

IMHO, using an early generation cross as a breeding parent can be really fun, especially if you have LOTS of space to grow a ton of plants out.

[bower]

+1 for the variability. I've seen wonderful tomatoes come out of crosses between unstable generation parents. I think it gives you a better chance of finding something unique and truly surprising. Tom Wagner put me onto this technique and I have all good things to say about it.

[crmauch]

I would say if you know specifically what you are breeding for, it would be better to start with stable varieties that have the genetics you're looking for. If you want to combine multiple varieties and see if any thing interesting comes out, then I think breeding with the F2 or F3 is quite fine.

Another difference would be that when crossing stable varieties you would start with a small F1 generation (the seeds of your cross) and then plant larger amounts of F2 and start selecting there.

If you are crossing unstable varieties, you'd want to plant far more seeds of your initial cross (your F1) and start selecting in that generation.

[tpeltan]

The main advantage is you will get diverse population as early as the first generation after the cross. This might also be a disadvantage as you might need more seed from the cross (with stable parents you need only one F1 seed (in theory) as all F1 seeds and plants are genetically identical - but with F3 line as one parent all seeds will be different so you might need many of them).

[tpeltan]

Originally Posted by crmauch

I would say if you know specifically what you are breeding for, it would be better to start with stable varieties that have the genetics you're looking for.

There might be an exception if you want something you can't obtain by simple crossing of existing stable lines. Your initial F2 (F3) generation might combine several important traits for further breeding on one parent(e.g. disease resistance...) and then you add the other parent for further desirable traits.

[KarenO]

How can you identify a plant with the “desired characteristics” until the end of the season with ripe fruit when it is too late to do a cross.
Plenty of stable tomatoes with dependable genetics to use in crossing. The only place using early segregates to cross is really useful or adventageous is in backcrossing your own cross to an earlier segregant to increase the odds of recovering a specific trait.
Otherwise unless you have space for growouts of large numbers of F2 plants it’s a genetic crapshoot and will be more difficult to stabilize.

KarenO

[BoilerMan1812]

Thanks all for the replies. I think I’ll go ahead and use the F3 in a few just for fun.

Karen,
There are certain leaf and growth characteristics that I can evaluate prior to making the cross but obviously I wouldn’t be able to evaluate the fruit and production prior. My plan is to make multiple crosses early, then at seasons end I can decide which to grow out.

[KarenO]

I am also assuming the F3 you intend to cross is one of your own? If not it is good form to seek the approval of the breeder you got it from.
KarenO

[bower]

Originally Posted by tpeltan

There might be an exception if you want something you can't obtain by simple crossing of existing stable lines. Your initial F2 (F3) generation might combine several important traits for further breeding on one parent(e.g. disease resistance...) and then you add the other parent for further desirable traits.

Exactly! Not everyone has two ideal OP parents to get all the desired traits from a simple cross.
I have made many crosses toward the end of season or after first fruit has ripened and been tasted and evaluated. That's here with a nominal growing season of 2.9 months. So by no means out of the question. I've even made crosses in September - really the end! of our season, and managed to get seed. Many times.
There's no reason not to use an F3 for a cross, if you see that it has a number of the traits you desired and had a parent available with the complementary traits.

I don't know of any breeders who object to the use of unstable material for other crosses, other than perhaps KarenO. The only real advantage of making a simple cross between 2 OP's, you only have to grow seven generations and you're done.

[tpeltan]

Originally Posted by bower

The only real advantage of making a simple cross between 2 OP's, you only have to grow seven generations and you're done.

There should be no difference in the "seven generations and you're done". The only difference is in the F1 generation.

[bower]

Originally Posted by tpeltan

There should be no difference in the "seven generations and you're done". The only difference is in the F1 generation.

Absolutely right. What I meant was, when you take a cross at F3 and cross it again, you are starting over again at year 1 of 7.
If you're lucky enough to have all the traits you needed in two parents of a primary cross, then you can select the tomato you want in just seven years, which is great!
If you need to do a side cross along the way, to combine traits from another parent or parents, it is a longer process overall.