can someone please help me work out the genetics

[tessa]

hi everyone...

i've been quietly working away (all alone. woe is me ) on stabilizing a tomato that popped up in my garden several years ago. i'm calling it 'tessie's treat' because it is, hands down, the finest tomato i've grown since becoming a tomato-nutter just like most of you and it is the one i look for when searching for the perfect tomato for my sandwich.


it all began when i grew out some 'earl's faux' seeds that i got from grub.
i was happily growing away and posted a pic of it in another forum, and someone pointed out that it couldn't be an 'earl's faux' because it was regular leafed.
hmm.

so i sewed a few more of grub's seeds and found a mixture of regular, and potato leaves in the seeds that he had sent me. so it was a cross, and probably not a first generation cross because THAT should have come out ALL regular leaf, right?
so that is question number one: would a first generation cross have come out all regular leaf?

so then i went on to cull any potato leafs that popped up in subsequent generations and have been growing out the regular leafed plants for several years. i'm now up to F5...and lo, behold, a potato leaf has reared its head again.

so my question on that is: what do i consider this potato leafed plant to be? is it, in fact, an 'earl's faux'? or is it a potato leafed variety of 'tessie's treat'? OR, is this ANOTHER unintentional cross now showing up in the F5 generation?

what say you all?

[dice]

probably not a first generation cross because THAT should have come out ALL regular leaf

If it were an intentional cross, where the bud on the Earl's Faux plant
had been trimmed before it could self-pollenate and then hand-pollenated
with pollen from the RL parent, that would be true.

For a chance cross, however, the fruit can have a mix of self-pollenated
seeds (PL if the fruit is an Earl's Faux fruit) and cross-pollenated seeds
from a bee (can be PL or RL, depending on what kinds of pollen the bee
had stuck to it when it visited the flower that fruit came from). One bee
can supply multiple different cross-pollenations at the same time.

edit:

i'm now up to F5...and lo, behold, a potato leaf has reared its head again.

Another bee saying hello would be my guess.

[Fusion_power]

Since the PL gene is recessive, it could exist in the background for several generations without your detecting it. The way to be sure is to do single plant seed saving. This means to save seed separately from each plant you have selected to grow plants from. Then when you plant those seed, look to see if any of them show up as PL. If they do, then you know the parent plant was carrying a hidden PL gene. I used this exact procedure to stabilize Taps which has for years been reported as a variety that often throws PL seedlings. Now I have a PL version of Taps and a RL version of taps that both breed true.

DarJones

[carolyn137]

Originally Posted by Fusion_power

Since the PL gene is recessive, it could exist in the background for several generations without your detecting it. The way to be sure is to do single plant seed saving. This means to save seed separately from each plant you have selected to grow plants from. Then when you plant those seed, look to see if any of them show up as PL. If they do, then you know the parent plant was carrying a hidden PL gene. I used this exact procedure to stabilize Taps which has for years been reported as a variety that often throws PL seedlings. Now I have a PL version of Taps and a RL version of taps that both breed true.

DarJones

About Taps.

Darrel, I first listed Taps in the 1997 YEarbook and said that Jim Garvey had been working with this PL variety that he bought from Pepper Joes, yes the same Pepper Joe who is Penny's husband.

Jim was a good friend of Craig when he lived in PA.

And I listed it as PL, as Jim said it was,but saved seed gave me both RL and PL plants, three years in a row of sperate selection, so for me it flip flopped on leaf form but all else was the same.

So I'm the first person who reported the flip flopping and Craig heard me complaining and I wasn't going to fool with it for a fourth year so he ssaid send me the seeds.

And I think it was by 1980 that he had the PL and RL stabilized. I don't know if you knew that.

I didn't take the time this AM to look at listings for Taps from my seeds first offered in 1997 for the simple reason that the swelling around my eyes still maked it difficult for me to read.

[tessa]

thanks for your replies, everyone.

fusion...
so i'm just not clear on one thing:

one parent of the original cross was PL. earl's faux. but i've been saving only from the RL plants that have shown up. the original RL was a definite cross, hence the RL.
but after 4 generations of selection...is the PL that pops up an earl's faux? or because it's lineage was from a DEFINITE F1 cross...does this make it a PL variety of the new cross?
the genes, no doubt, are a throw-back to the original parent.

[dice]

What Darrell is saying is that in the F1, you have a gene pair for leaf type,
with a dominant RL gene and a recessive PL gene (leaving out all
of the other details like rugose, cerasiforme, etc that alter the leaf
without changing that major dichotomy between RL and PL). The F1 plant
has RL leaves.

In the saved seeds from that F1 plant, you can have RL-RL, RL-PL, and
PL-PL gene pairs. RL-RL and RL-PL in the F2 plants both have RL leaves,
and a PL-PL F2 has PL leaves. If you save seeds from a PL F2 plant, the
F3 seeds can only have PL-PL gene pairs (leaving out bees, etc). There
is no source of RL leaf type genes in that PL F2 plant.

If you save seeds from an RL F2 plant, however, it could be an RL-RL F2,
in which case all of the F3 plants grown from those saved seeds would be
RL, or it could be an RL-PL F2, in which case the F3 seeds could still have
RL-RL, RL-PL, or PL-PL combinations, so could still produce a PL F3 plant.

As you save seeds from RL plants each year, you do not know if you are
saving seed from an RL-RL plant or an RL-PL plant, so the PL gene could
still be lurking in there, ready to produce a PL-PL gene pair in a saved,
self-pollenated seed that will produce a PL plant when that seed is planted.

That could have been how you got a PL plant in the F5s without the
assistance of a bee pollenating the F4 (edit: an F3) plant that you
saved seeds from.

edit:

does this make it a PL variety of the new cross?

Yes. The other genes have been randomly pairing between
the Earl's Faux genes and the RL parent genes from the beginning.
Each gene pair does not stabilize until you get a matching
dominant-dominant or recessive-recessive gene pair by chance
in a saved seed.

The chance that those would all arrive at the same
dominant-dominant and recessive-recessive pairs as an
Earl's Faux plant after 5 years of growing out the generations
of the original cross is *extremely* small.

[tessa]

Dice, thanks SO much for this thoughtful and detailed answer. I totally get it now.
So what I can be doing now is stabilizing the PL variety knowing it's not an earl's faux.

[Fusion_power]

Tessa, given the number of generations you have grown this plant out, the PL plant will most likely already be stable. This presumes there are no bees wandering around doing their buzz thing.

DarJones

[Templeton]

Originally Posted by tessa

hi everyone...

i've been quietly working away (all alone. woe is me ) on stabilizing a tomato that popped up in my garden several years ago. i'm calling it 'tessie's treat' because it is, hands down, the finest tomato i've grown since becoming a tomato-nutter

Tessa, can always find room for a few SH grow outs if you need some help... (he impulsively offers....)
T

[Fusion_power]

Look what you started Tessa!

[tessa]

LOL, fusion. it feels good to start a thing or two, eh?

templeton:
send me your address and i'll send you some seeds.
it would be nice to have someone outside of my own address give this tomato a rating.
i think it will be worth the space

[stonysoilseeds]

i know this is an elementary question and this migt not be the appropriate thread to post.. i am unclear on how many generations you need to grow out tomato varieties to achieve stability does it vary with varieties... and when it is an F6 does that mean its the 6th year of growing this variety.. i am newer to the aspect of saving seed and would like to learn all i can about the subject so any help would be appreciated.. thanks all

[travis]

F2s are 50% homozygotous (stable for only 50% of the recombined gene pairs), F3s are 75% homozygotous, etc., etc., etc., until F6 (which is your question) are still 3.125% "unstable." F7 seeds from a cross made 7 growing seasons past, and a point at which many people assume sufficient stability, are still 1.5625% unstable, and could possibly throw from a batch planting a single recombining seedling expressing a recessive trait such as potato leaf, clear skin, yellow or bicolor flesh, etc., etc., etc.

So as you can see, continuing into future generations halving the percentages of remaining instability, the instability of genes remains even to an infinitesimal likelihood of one seed in a batch of previously totally stability-apparent germplasm popping up with a lurking expression of whatever. Slim, slim likelihoods, but still there.

Second question: "Does it vary with varieties." Answer: Yes, it might appear to vary with varieties, because for example, many modern tomato breeders are breeding commercial cultivars using very similar parent lines. The reason is that those breeders are shooting for traits such as disease tolerance, extended shelf life, shipping and storage condition tolerant qualities, etc. And most of those standard commercial tomatoes also have dominant traits such as red flesh, yellow epidermis, regular leaf, etc. So, with those varieties (or rather breeding lines), when the cross is made, the future generations, if one chooses to grow out filial generations from a commercial hybrid, the dominant traits sort of camoflage "instability" even to the point that some people think the hybrid itself is stable. It's not.

But if you cross highly diverse parental lines, you will see some wild diversity in the filial generations. For example, if you were to cross an old fashioned, potato leaf, green when ripe, clear skinned beefsteak (Green Giant), with a regular leaf, tongue shaped, skin striped, red fleshed, yellow skinned tomato (Speckled Roman), you might "see instability" for quite a few generations.

[dice]

Originally Posted by stonyoilseeds

i am unclear on how many generations you need to grow out tomato varieties to achieve stability does it vary with varieties...

It does vary, not so much with variety but with chance:
http://kdcomm.net/~tomato/gene/genes2.html

Stabilization is probabilistic. That means that probably you get
matching gene pairs in so many years. The improbable (not yet
stable at F10 or whatever) is always possible, it simply does not happen
that way very often.

Originally Posted by stonyoilseeds

and when it is an F6 does that mean its the 6th year of growing this variety

6th generation from the initial cross.

[travis]

Yes, filial generations and growing cycles do not necessarily always mean years as you may grow two successive crops outdoors in a single year, or in greenhouses; and depending on where you live I suppose you could grow three successive crops in a single year.