Selection of F3 plants
 

I am growing out 16 F3 plants this year and I have about half of them that are growing way slower than the other ones. Should I give up on them now because they lack vigor or should I continue growing them to see if they catch up?
Mike

That is the original cross? Was the "vigor" uniform in the F2 plants? What did you select for in the F2, and what was your criteria for culling in the F2 plants?

When you say half your plants are growing way slower, how old is the entire lot? Do you mean slower in overall growth, less vigorous over all, or slower to develop flowers and fruit?

This is a grow-out of a hybrid that came to my garden as a volunteer (2 plants). I thought it was a yellow pear, which was the only OP in my garden the year before but it turned out to be two productive plants with medium sized red fruit so I continued work on growing them out. So really there was no selection in the F2 besides yes or no.
My plants are all about 4 weeks old and many of them are starting to get their second set of true leaves. The ones I am concerned about only have one set and are still very small (leaves and height).

Ah. The original plant that left the fruit that the volunteers
came from was a commercial F-1, the volunteers last year
were F-2, and this year's plants are F-3. Unless you were
a professional plant breeder, you probably would have no
idea about the parents of the original F-1 (and you might
not be able to find out even if you were; trade secrets, etc).

Hard to say about the small F-3s this year. If I were growing
them and I had enough space, I would grow all of them, and
not give up on the small ones until I had seen ripe fruit at least
(or until something in the garden kills them off or whatever).
Those might be the best tasting ones, might be most productive
in summer weather, etc, even if they were the weaker seeds at
seed-starting time.

If space is limited, it is your call whether to insist on vigorous
seedlings as a selection criteria.

I will try to grow as many as possible-I have room for about 20 plants in my garden, and I have about 60 stared. 16 are the F3. I better get out the tiller.

I also notice that the smallest of the F3 plants has 3 cotyledons. At first I thought it was PL but now it has true leaves RL. Any explanations?

3 cotyledons ("tricots") can mean a mutation that makes
the whole plant infertile (triploid), or it can be a chance
mutation that only affects the cotyledons themselves, with
the plant reverting to a normal tomato plant as soon as
the true leaves develop.

One thing that you could do with the F-3s is space them
close together, like 12-16 inches, and prune them to a
single main stem. You will not know how the whole plant
produces unpruned, but you can still compare one to another
among that generation as to overall plant vigor, flavor,
production, size and quality of fruit, etc.

I also notice that the smallest of the F3 plants has 3 cotyledons. At first I thought it was PL but now it has true leaves RL. Any explanations?

Not sure why my post was repeated. Sorry. Thanks dice. I had not heard of a tricot before. Does it happen often because I haven't seen it before? Or is it more common when doing a growout?

I usually see a few every year. Varieties where they occur seem
to be random.

Most of the documents on the WWW discussing tricots are
effectively horticultural rocket science (without a relevant
education in the field, one starts to get lost in the terminology
about the second paragraph).

I have seen a diagram of what happens inside the nucleus
of cells of tomato plants with 3 sets of chromosomes instead
of two (completely triploid plants). It is a genetic mess, and
those plants are usually infertile.

Tricots are not all triploids, though. The two cotyledons of a
normal dicotyledon plant are part of seed development
before the seed is ever planted, and mutations that only
affect that stage of seed formation without affecting the
subsequent development of the whole plant after the seed
sprouts seem to be fairly common.

There is a theory that producing tricot seeds is an innate ability
of some kinds of plant that is switched on chemically in
particular, apparently rare environmental conditions.

Can you imagine the theories of farmers 2000 years ago when
the occasional tricot seedling emerged in the spring (not
necessarily a tomato plant)? "Is it a blessing or a curse? Or
perhaps it is simply an omen? Should we plant more seeds
this year?"

So I ended up getting 13 of my F-3 plants in the ground and all of them are now growing well except the tricot. All of the plants look very similar at this point but they are the last of about 20 varieties in my garden to produce flowers. Hopefully the fruit ripens quickly- I don't see any advantage in developing an extra late variety in zone 3.

The tricot probably has more than just the cotyledons that has mutated
(not for the better, apparently).