My Unintentional Cross

[J Peazy]

Last winter I sent seeds to a woman in California who had posted to a seed wanted/gardening forum.

I thought I was sending her Black Prince seeds. It looks like the bees did some magic at the end of the season.

She posted some pics of the vegetables she had grown to her blog. Her pictures had the caption Black Prince tomatoes - but these guys looked weird to me. She swears there was no labeling mix up on her end.

Please see attached. I think they crossed with the F2 plants from a grocery store Roma that I planted for kicks.

Notice the cluster in the last picture. I don't remember my Black Prince plant clustering last year. Do Black Prince tomatoes do this? What do you think of these?

[dice]

The clustering, that could just be a really healthy plant. Black Prince
is quite productive. But the fruit shape is wrong, Black Prince produces
round fruit. That looks more like Japanese Black Trifele.

Black Prince: http://www.tried-and-true.com/new/wp...to-300x230.jpg

Japanese Black Trifele: http://www.ghorganics.com/Japanese%2...feleTomato.htm

[J Peazy]

I don't know if this is two or three different plants. Only one has the green shouldered fruit that I remember from last year.

Is black fruit color dominant over red?

Are certain fruit shapes dominant?

Thanks,

[dice]

Is black fruit color dominant over red?

No, red is genetically dominant. I crossed Black Prince with Romeo,
a large, red, late-season, elongated paste tomato. The F1 fruit were
round and slightly oblate, red with green shoulders.

Are certain fruit shapes dominant?

I would guess round oblate, not elongated, from the results above,
but I have not looked it up in any kind of tomato genetic index.

If you have not grown Japanese Black Trifele or a similar shaped
dark tomato, then you probably have Black Prince crossed with
one of your hybrid romas or similar. The F1 fruits would have
likely been red, but if the roma itself was F1 or F2 (thus not
necessarily homozygous for color), then other colors are possible,
depending on what the parentage of the F1 roma was.

It goes like this:

OP x OP - whichever one has the genetically dominant color,
that trait will show up in the F1 plants; plants grown from
seeds of this cross should all be the same.

OP x F1 or F2 - other colors are possible if the OP was not itself
a genetically dominant color; plants grown from seeds of
this cross will fan out like F2 plants from seeds of a self-pollenated
F1 fruit, with each plant being a little different

Tomato Gene Basics:
http://kdcomm.net/~tomato/gene/genes.html

Mendel's Peas:
http://tomclothier.hort.net/seedsav3.html

An index of identified tomato genes:
http://tgrc.ucdavis.edu/Genes.html

One complicating factor is that what looks to us
like a trait that would be controlled by a single gene
is often controlled by multiple genes.

[J Peazy]

Dice,

Thanks for all of your help. I appreciate the links - very interesting.

The seed packet I sent held seeds from about two or three different tomatoes. One had sunscald and another had a hole poked into it by a stinkbug if I remember correctly.

I have never grown Japanese Black Trifele. Actually the Black Prince was the only black tomato I have ever grown.

Is it likely that my "Romas" were F2 with the F1 parent being in the field?

I posted some pics and info related to this year's "Roma" F3 to the thread below and got an interesting response from Travis. http://www.tomatoville.com/showthread.php?t=18488

The "Roma" F3, as it turns out, is a 2 oz round tomato that grows in clusters of 6. They seem to want to ripen uniformly.

If the clustering tomato from the last picture turns black, and black is recessive to red, then is it most likely that the plant in that picture is probably a true Black Prince given the Roma has a grocery store lineage? Would a breeder of a grocery tomato ever use a black heirloom to create a field production tomato tolerant to Mexico's heat?

Thanks again for humoring me.

JP

[dice]

Is it likely that my "Romas" were F2 with the F1 parent being in the field?

I would guess that the grocery store roma was an F1,
from a self-pollenated fruit. When you grew seeds saved from it,
those were F2 seeds. Each had more homozygous gene pairs than
the F1, but (remembering the Tomato Gene Basics page) it was
still not genetically stable (not all gene pairs had two of
the same gene).

Then it crossed with Black Prince, giving you a new F1 from
a stable OP x unstable F2 cross. This might as well be a new
F2 as far as what to expect from the plants. Each plant will
have a slightly different mix of genes for color, flavor, size,
growth habit of the plant, etc. Any plant with a gene for red
fruit will still produce red fruit, whether that gene pair is
homozygous or not (a gene for red paired with a gene for black
will still produce red fruit). That fruit may or may not have
green shoulders, because that is a different gene than overall
fruit color. (Ditto for stripes, unusually intense red color,
etc.)

A graphic of fruit shape mutation:
http://www.plantphysiol.org/content/...expansion.html
(The abbreviations probably refer to gene names or allele names
or something like that.)

Cerasiforme is just the cherry tomato variation. The originally
developed cherries had rather small leaves compared to larger
fruited tomatoes. This page explains the various groups of types
of tomatoes:
http://www.kdcomm.net/~tomato/Tomato/ecomplx.html

Breeders have used wild types to introduce disease resistances.
They might also use a cerasiforme cultivar (cherry tomato with
small leaves and fruit) that already has that disease resistance.
If a black tomato were used, it would probably be for flavor and
perhaps cold tolerance (or who knows; there are a lot of genes to
account for in a planned cross when you are thinking about it at
that level of understanding of the plant).

When I grew Black Prince, it grew fast early in the season, had
good flavor and production, but it had virtually no resistance
at all to verticillium wilt. Another plant next to it might lose
a branch or two, while the whole Black Prince plant would crash
and burn in a week from the same disease.