I do agree with maf, and @KaguyaCloud I hope you won't be too disappointed if leaf number turns into a rabbithole due to the environmental influence - even growth rate and pot size as maf pointed out, - there always seems to be some number of variables beyond our actual control, even in a controlled environment.
Your instinct to pay close attention to details is a winner. This is a talent that you'll enjoy and find many payoffs in the breeding process. It just seems to me based on my own personal experience with growth habit, that the environment plays such havoc and gene expression is so complex on top of the complexity of the genetics, it is a very deep rabbithole where I could never find the rabbit.
Nothing wrong with that in itself, just that the results in a given season say less about genetics than we might have hoped.
Keep on, however, until you're satisfied that you've gotten to the bottom of those details. I'm still hopeful that you might get some valid conclusions for the controlled environment - which could be proven by repeating the experiment with different pairs of parents that have the same leaf patterns. I still think it may be impossible to replicate those results in other environments, but I could be wrong.

Loved your history of MicroTom btw. Very useful to share that deep documentation.

I will take that advice to heart. Luckily I am not too worried about the number of leaves to flowers, it was an observation that I noticed. Replicability will likely be a very difficult issue to handle. Regardless of what the results may be, it's likely I'll learn something from this experiment. Considering how many different micro-dwarf varieties are available, I'm hopeful that selecting these traits are possible despite the lack of detailed documentation.

Keep up the good work. It is interesting to follow and much appreciated.

The genetic factor is clearly very important when looking at number of leaves to flower, it is just not the whole picture, which is what I was trying to point out in a clumsy way in my prior post.

KaguyaCloud wrote: ↑Sat Mar 16, 2024 12:48 am Update: 3/15/24

Confirmed that the flowers have began to open in my JoRo F1. This would make it 21 days to flowering from opened cotyledons for the hybrid cross. Plants are now 23 cm tall, which is about the same height as their parent Rosella Cherry. I accidentally snapped the flowering tip off the left plant in an attempt to bend it horizontally. Hopefully it recovers. With so many axillary shoots growing, I could just propagate another cutting in case of emergencies. If the growing tip doesn't survive, I could study the effects of side shoot growth of the axillary buds to see if there's any difference.

In addition, I would like to revise my previous statement on leaflet number as the leaves begin to fully mature. It is now this:
3, 5, 5, 7, 7.

In terms of leaflet number, it seems to follow the pattern similar to Vilma, a variety with unreduced leaf but early main stem termination. This is promising, as it seems that the leaf reducing gene is mostly recessive.

Also some other noticeable observations:
-Smaller number of leaves to flower is...strange. F1 grew 7 leaves before putting out a flower truss. Jochalos grew 9 leaves and Rosella Cherry grew 8 leaves before producing a flower truss.
-F1 flowering pattern seems to look normal to a regular flowering pattern for indeterminates, where there is 3 leaves for every flower truss that grows.
-Creating a heavy number axillary shoots seems to be dominant
-10+ flower trusses in Rosella Cherry is dominant over 5-8 flower trusses in Jochalos.

Every time I see that you have flowers or ripe fruit so quickly, I am jealous of you.

Doffer wrote: ↑Sun Mar 17, 2024 9:58 am Every time I see that you have flowers or ripe fruit so quickly, I am jealous of you.

If it makes you feel better, most of the micro-dwarf varieties minus orange hat tasted not great in the end.

Also update 3/17/24
Flowers bloomed and found some interesting things: https://imgur.com/a/XARNk32
Jochalos, like Orange hat and other micro dwarf tomatoes, differs from cherry tomatoes in that they have more than 2 locules in their fruit. The gene responsible for this also changes the number of petals and sepals that the flowers have.

Jochalos typically has 6 sepals, 6 flower petals, and more than 2 locules.
Rosella Cherry has 5 sepals, 5 flower petals, and only 2 locules.
The F1 JoRo has 6 sepals, 6 flower petals, and unknown number of locules.

-It seems that 6 petals may be dominant over 5 petals. This also confirms that the cross was indeed successful, as the larger parent only produces 5 petals.
-Fused sepals from Rosella Cherry also seems to be a dominant over separated/unfused sepals from Jochalos.

I'm somewhat glad that I chose two parent plants with so many different traits from one another. The F2 generation is going to have a lot of variation. It's a shame that I'll have to cull off the ones without micro traits, but I could continue propagating the F1 and save seed from it.

The cherry condition (2 locules) should be dominant. But wild type can have 3 locules in some cases. So your F1 should have 2 or 3.

There are two genes involved in more locules: "locule number" (lc) and "fasciculated" (fas).
Iirc, lc/lc is expressed with or without fas, and produced up to 5-6 locule fruit, but fas is not expressed unless lc is also present. fas drives locule numbers greater than six.
Elsewhere I'm seeing these described as QTL's, and that makes sense in terms of the variation possible.

Petal number and flower size and shape can be a good tell for the fruit shape, in segregating crosses involving multi-locule and cherry fruit. Petal number tends to vary though, on a given plant. Flower form is extremely sensitive to environmental triggers (see megabloom discussions for example). Even a different position in the canopy can trigger differences in petal number etc. But a cherry will not produce a 'megabloom' type flower with extra petals, large anther cone, etc. Those flowers are certain to produce multilocule fruit, so you can select for the fruit shape at flower stage to an extent.

Fused sepals - I think there may be genetic tendencies (susceptibility) but sepal fusion is still mainly environmental. That opinion is based on seasons when there was a lot of it across the board here in unrelated lines, and other seasons not. But I may have overlooked the strength of genetics for this, if the most affected line wasn't grown forward.

Regarding fused sepals, I've grown Rosella a few times and can confirm that it has a high incidence of fused sepals, more than any other cherry tomato I can remember growing. (That plant has some interesting genetics, I would love to know what it was bred from...)

Rosella also has an excellent flavour profile, so if anything can save the micro tomatoes from tasting "not great in the end" then Rosella is a top candidate. It also was developed as a greenhouse variety so likely to have some resistance to indoors type tomato diseases which would be beneficial in a micro.

Flower form is extremely sensitive to environmental triggers (see megabloom discussions for example). Even a different position in the canopy can trigger differences in petal number etc.

Oh for sure, during periods of neglect, low amounts of light, or low nutrient levels, I've seen micro varieties begin to only grow 5 sepals/petals instead of their typical 6 that they usually do. For the most part, it seems all the micro varieties I've grown so far don't really have the fasciated gene. However, I've only once witnessed micro variety Orange Hat to have grown 1 single fasciated fruit in the one year I've cultivated it. That might have been a freak environmental accident rather than genetics.

Regarding fused sepals, I've grown Rosella a few times and can confirm that it has a high incidence of fused sepals, more than any other cherry tomato I can remember growing. (That plant has some interesting genetics, I would love to know what it was bred from...)
Rosella also has an excellent flavour profile, so if anything can save the micro tomatoes from tasting "not great in the end" then Rosella is a top candidate. It also was developed as a greenhouse variety so likely to have some resistance to indoors type tomato diseases which would be beneficial in a micro.

I've also experienced this as well as it was one of the first things I've noticed in this particular variety. I found some interesting research on fused sepals. It seems that the gene SIAGL6 is one possible candidate for a reason why the sepals were fused, as down-regulating this gene causes more incidence of sepal fusion. What I have found most interesting is that suppression of this gene upregulates SlGLK1 and SlGLK2, which is associated with increases in carbohydrates and carotenoids in ripe fruit.: https://sci-hub.ru/https://link.springe ... 017-2129-9

Down-regulation of SlAGL6 led to light green petals with increased total chlorophyll content and up-regulated chlorophyll biosynthesis genes SlGLK1 and SlGLK2.

And for sure, if I ever manage to figure out how difficult it is to stabilize the micro traits, I will likely backcross the plant with it's parent Rosella again. It's also nice to know that Rosella has some genetics for indoor greenhouse disease resistance.

Very cool! Thanks @maf and @KaguyaCloud for clarifying the genetic basis of the fused sepals.
I can't remember which line it was/which year it was that I had more than usual fused sepals. I do recall that there were heart genes involved ie long shape, no idea if there's a linkage to that?
Will keep an eye out for the fused sepals when I'm growing out old or back burnered lines.

bower wrote: ↑Sun Mar 17, 2024 4:07 pm I can't remember which line it was/which year it was that I had more than usual fused sepals. I do recall that there were heart genes involved ie long shape, no idea if there's a linkage to that?

Based off this research article, it seems to be located in chromosome 1. SIAGL6 seems to be associated with parthenocarpy and heat tolerance for fruit setting as well. https://bmcplantbiol.biomedcentral.com/ ... 018-1285-6

Using quantitative trait locus (QTL) analysis for parthenocarpy and seed production, we detected a major QTL for each trait on nearly the same region of the Pat-k locus on chromosome 1

Week 4 Joro tomato update:
https://imgur.com/a/hdUNYA0

The plants are now 40-45cm tall with 3 flower trusses. Here are some things I've observed so far:
It seems that indeterminate growth habit is completely dominant over all the known dwarf traits, there are around 3 leaves between flower trusses and there is no sign of termination. The axillary shoots also grow about 7 leaves before they flower as well, which might suggest that the micro-dwarf trait that skips number of leave to flower in axillary shoots may be recessive.

Flower number now seems to be intermediate from the parents.
Jochalos has 5-8 flowers and no branching.
Rosella cherry has 13+ flowers on the first truss and potential branching on the following trusses.
Joro F1 has 9-10 flowers with no observed branching in the upper flower truss.
It seems that number of flowers is incompletely dominant and truss branching might be a recessive trait.

In addition, it seems that compact flower trusses are either dominant or intermediate compared to longer/normal flower trusses, as the F1 flower truss is less than half to a third the size of Rosella Cherry's flower truss.

I am also performing a propagation experiment on the F1 hybrid. Due to the sheer height and confirmation of the growth habit, it is more efficient to trellis the vine horizontally rather than vertically to maximize the light coverage per leaf. I have had really good success as I have grown a 120cm(4ft) indeterminate Rosella Cherry in a 4 inch pot utilizing this method. The vines are coaxed and bent when reaching the end of the grow light. Tracking how much water the plant used and keeping the soil very moist to essentially being soaked in nutrient solution prevented flower drop.
https://i.imgur.com/MVGIYXM.jpeg

What about a vertical growlight for the long vine?

Doffer wrote: ↑Sat Mar 23, 2024 2:39 pm What about a vertical growlight for the long vine?

That could work in an enclosed system. However, hanging the lights I currently have may be quite tricky and I could be blinded when tending the plants or walked the wrong direction in my open set up.
Then there's the issue of bending the vine and coiling it to grow downward once it reaches the top of the vertically placed grow light. Plants tend to grow upwards against gravity, so having to constantly adjust the growing tips to grow downwards might be somewhat problematic.

Update 3/25/24:

Very interesting observation. It seems that flower cluster branching may actually be a dominant gene, as the third flower truss on the left Joro F1 exhibited branching behavior along with a leaf weirdly growing in the truss. I'm unsure if leaf growth within a flower truss is normal, as I have not seen this exhibited in either parent variety. At the very least, branching potential is possible.

The branching characteristics in Rosella Cherry is rather odd. It isn't like the varieties with the multi-flora gene. The branching isn't too extreme, with usually around 20 flowers per truss when it branches.

That's a beautiful cluster
Flower truss patterns are really interesting. Besides the branching, which basically doubles your fruit numbers per truss, there are distinct patterns - the ladder, typical of cherries, and then, variations on a more sprawling branch pattern, in some larger fruited varieties. There is also a gene that suppresses or halts the truss branching in some varieties - probably selected to optimize fruit size and overall loading on the plant - which can be lost in some F2's and giving rise to offspring with huge (or even infinitely) branched clusters from a small truss parent plant. There are some large fruited varieties that go with the simple ladder type truss and limited numbers - cv's designed for production with clusters that self support or fit well with a simple fruit support system. So there's quite a lot of play in the truss architecture and some nice surprises.

I have a beefsteak X Rosella F1 (no dwarf, no micro) trialling this year so will update on how the fruit clusters look when in this combination. Might provide data about Rosella crosses that can be cross referenced to your project....

My backcross to Orange banana has the first flower.
Seeding at 15-02
flower at 27-03
So i took 41 days to get a flower. The other 19 plants still have flower buds.

I hope i can recognize the tangerine plants because of the orange flowers.

I have a beefsteak X Rosella F1 (no dwarf, no micro) trialing this year so will update on how the fruit clusters look when in this combination. Might provide data about Rosella crosses that can be cross referenced to your project....

That might be interesting to see what the cross comparison might be. Judging by what I've observed, it's possible that there will be:
Intermediate fruit set that is leaning towards cherry.
Branched fruit trusses
More than 8 flowers per truss.
More than 5 sepals/petals
Fused sepals
Uncurled sepals.

So i took 41 days to get a flower. The other 19 plants still have flower buds.
I hope i can recognize the tangerine plants because of the orange flowers.

Not a bad timing! Do you track days from the moment of germination or when the seedlings have opened up their cotyledons? If I remember correctly, I think @bower did some trials involving the tangerine gene.

Update: 3/28/24


More observations. The uniform ripening gene is recessive as expected. Rosella Cherry has a very small patch of dark green on the top, which may indicate that it does not have the uniform ripening gene. However, one interesting thing is that the developing fruit of the F1 is noticeable darker than both parent counterparts.

Sepal curling seems to also be a recessive gene, as there isn't a prominent curling structure in the F1 hybrid as the fruit develops over time. Fused sepals are still prominent in the F1 as the fruits develop.

Longer sepals from Rosella Cherry also seem to be dominant over shorter/proportional sepals from Jochalos.

Awesome looking truss. It's a real treat to see the generations flying by so fast.