If 2 genes are on the same chomosome, it will not say they are linked. Only genes that are realy close on the chromosome they have some linkage.

Actually since cherry (2 to 3 locule) is dominant, any plants with more than 3 locules should be stable homozygous for 'locule number'.

I'm not entirely sure how far the locule number locus is from the dwarf gene locus on chromosome 2, but you are correct since linkage is determined by distance between two genes in a chromosome. However, all subsequent generations had at least 3-6 locules in their first fruit.

I'm mainly focusing on the strange dominance between 2 locules and 3 locules. Rosella Cherry is strictly a 2 locule fruit with flowers that have only 5 sepals and 5 petals while Jochalos is a 3+ locule fruit with 5-6 petals and 5-6 sepals. When growing out the F1s, 3 locules is incompletely dominant to 2 locules(some expressing 3 locules and some expressing 2). I have yet to obtain a plant with strictly 2 locules with 5 petals and 5 sepals, so it's likely that this specific phenotype is recessive if the genes are not linked.

I'm really not sure about 3 vs 2 locules. Both are considered the dominant 'wild type' over multi-locule fruit; I have seen lines that continued to have fruit with both locule numbers, and put it down to gene expression.
But maybe I didn't pay close enough attention. I'm remembering now, quite some years ago I selected a 3 locule fruit from a cross with the dwarf Al Kuffah, which iirc also had consistently 3 locules.
So it seems that 2 locule and 3 locule must be different alleles of the wild type, and can be stabilized in one form or the other.
I guess your cross between 2 and 3 is the perfect way to find out.

Update 12/16/24


Joro F3-1 has turned its final color, making it 55 days from open cotyledons to ripe fruit. Final color is like its pale F2 parent, being a clear skin yellow tomato. In any case, I will wait 1-2 weeks for the seeds to mature from this stage just to increase germination percentage. The F2 parent has retained the trait that makes it very soft once fully ripe.

Joro F3-2 is possibly ripening? I'm unsure. The half of the skin of one of the fruits is turning translucent, but maintains a green color. It's still possible that this F3 is homozygous for the green flesh gene, making a green when ripe tomato, but I'm not entirely sure what a green when ripe tomato looks like as it ripens. I do know that the visible flesh of tomatoes with clear skin become less opaque as it ripens and turns to its final color.

bower wrote: ↑Fri Dec 13, 2024 6:13 pm Actually since cherry (2 to 3 locule) is dominant, any plants with more than 3 locules should be stable homozygous for 'locule number'.

2 to 3 locule?

What am I supposed to do with my boat-shaped white (pale yellow) 3/4" width X 1 1/4" length X about 7/8" height, 14 locule, F3 experiment?

Do I get to call it a cherry, if I can get it to retain that shape?

Tormahto wrote: ↑Tue Dec 17, 2024 7:50 pm

bower wrote: ↑Fri Dec 13, 2024 6:13 pm Actually since cherry (2 to 3 locule) is dominant, any plants with more than 3 locules should be stable homozygous for 'locule number'.

2 to 3 locule?

What am I supposed to do with my boat-shaped white (pale yellow) 3/4" width X 1 1/4" length X about 7/8" height, 14 locule, F3 experiment?

Do I get to call it a cherry, if I can get it to retain that shape?

Nope! You might have to coin a new term for that one (mini beef is probably what it would be called).
With 14 locules, your experiment has both of the genes required for a big beef: locule number (the first 5-6) and fas (more than 6, requires locule number to be present).
The actual size genetics are another set of additive QTL's aka 'fruit weight' fw with several such genes involved. So you must've got some really lightweight allele values from a tiny parent, I take it.

Update 12/19/24:


Both Joro F3s are pale yellow and are giving extremely heavy fruit set with fruits that are up to 1 inch(2.5cm) in diameter. The longer cherry trusses overlap each other, making them look almost like a cluster of grapes. There's more fruit than there is plant in Joro F3-1 and it's likely Joro F3-2 will follow the trend. I never thought I would describe a truss of tomatoes as pretty before. I hope the flavor is good, at the very least. The stems of both plants are as thick as the indeterminate Rosella Cherry parent.

For some reason, all the subsequent individuals from F1-F3 have tomatoes that are at least 1.5-2 times larger than the micro parent, which might indicate that there might be a gene within cherry tomatoes that could be slightly dominant to the genes controlling fruit size in micros.

The plants are only 4-5 inches(10-13cm) tall. I estimate that there's around half a pound(240g) of tomatoes on each plant, each plant taking up about 0.67sqft(625cm2) of space. Total area one plant covers is 0.33 cubic feet(9,275cm3).

OMG @KaguyaCloud those are both really splendid!!!!
And such a short DTM. Very nice indeed!

I realy like it, the fruit on top of the leaves.

Update 12/22/24


Flavor, sweetness, and acidity is generally lacking for both F3s. F3-1 has slightly better flavor, but the fruit texture is quite...soft and mushy. The 2 locule trait is back, which refutes that the dwarf gene is linked with 3 locules, like Doffer has explained a week ago. So this likely means that 2 locules is recessive to 3 locules, as the first fruits of the plant that ripen usually can indicate the largest locule number.

Both of the first fruits are seedless, likely due to lack of pollen in the initial flowers. However, flowers that developed later have very high pollen count. This likely is a trait from Rosella Cherry, as it has slightly exerted stigmas in the initial flowers of the flower truss. The initial flowers of the F3s were split open at the anther cones, likely leading to no pollination. However, having parthenocarpic fruit isn't a total loss to me. The skins on both are quite thin, which is very nice to have. I will be saving seeds regardless.

I think the plan from now on is pursuing the backcrosses with the indeterminate Rosella Cherry, which I have already done for Joro F3-2. In terms of growth habit, Joro F3-2 is smaller and is the first individual in the project exhibiting the leaf senescence that is common in smaller micro-dwarfs during fruit set. Both have a more open growth habit, which I am some-what glad to have. Most of the smaller micro dwarfs grow a very dense canopy with hard to grasp fruits.

Hopefully I can introduce even more flavor genes without having to sacrifice for compact growth habit. And if that doesn't work, I think I will likely attempt to isolate as many individual micro traits to see which one is affecting flavor.

The parthenocarpic in interesting. Is this from Rosella or Jochalos?

I wonder if you get fruits when you cut off the pistil of a young flower that has not yet produced pollen?

Doffer wrote: ↑Sun Dec 22, 2024 1:25 pm The parthenocarpic in interesting. Is this from Rosella or Jochalos?

It's possible that it is from Rosella Cherry. Rosella Cherry is described to have very few seeds in the fruits and produces very little pollen in its flowers. Despite lower numbers of seeds, Rosella Cherry still produces decently sized cherry tomatoes(1-1.5 inches).

I haven't really tested taking the pistil off a young flower to determine if it is able to produce fruit, I may be able to try it out in a month or so. Backcrossing it with the parent should make it easier to determine if I am not prioritizing parthenocarpy.

Update 12/26/24:


Joro F3s are starting to ripen as I begin harvesting and weighing the first few fruits. So far, looks like all the fruits in the first few trusses are seedless. I could not find a single viable seed just yet. Flavor is still lacking, with low acidity and sweetness. It has practically all the fruit shape and texture of the parent Rosella Cherry.

I think for next year, I will go onto plan B on the micro flavor project, which is growing out the backcross I made of F3-2 with Rosella and performing a series of micro selections at the seedling stage. If the generation after the backcross still doesn't taste good, I will do another series of backcrossing. I will only be selecting for no closed cotyledons during the night cycle, small roots, and early termination.

Genetic distribution of the backcross(R is Rosella, J is Jochalos, het is Heterozygous for both)
BC1-F1: 50%R, 50% het
BC1-F2: 62.5%R, 12.5%J, 25% het

Second backcross if flavor is not good enough still
BC2-F1: 75%R, 25% het
BC2-F2: 81.25%R, 6.25J, 12.5% het

I should only take me 1-2 years to perform these series crosses, and another 2 generations to stabilize the rest of the traits. And if this does not work, Plan C would be to create separate lines of tomatoes, each containing a single micro trait.

Looking forward to your next generation.
These plants are so pretty. Just a thought, it might be worth growing more plants from the F3 to see whether the combination of flavor and sweetness is actually there. 2 plants really isn't enough to get the range of possibility.
OTOH your plan to stack the flavor genes through backcross could be the best time/space saver, just because the selection of traits that are easily seen early on is so much shorter a span. Since flavor is a full season growout/maximum time and space per plant. You may still have to grow more than 2 per generation though, or for sure you are missing out on what is possibly there in the flavor.

Thanks bower.
If I just had the space, I would definitely grow out more trials from the F3 generation. I still am keeping cuttings of each generation and all the seeds of the individuals that I have grown.

The one issue I had to begin with was that the parent pale F2 that I started with already had diluted flavor with zero sweetness and sourness. It's possible that sweetness may have already been bred out. The only reason I have grown out this generation is to see if the compact growth habit and early termination gene is stable, which it is. As much as I would like to attempt another generation of grow outs, the flavors have not really been meeting expectations(even less flavor actually). It's gotten the fruit set and low acidity of Rosella, but the diluted flavor compounds of Jochalos.

One advantage of backcrossing back to the parent is that it might give me more insight on whether being randomly 50% homozygous for Rosella Cherry(and 50% het) impacts flavor at all. There's no need to continue 4-5 more filial generations to see if the complete homozygous products with 50% homozygous genes to Rosella Cherry have retained flavor.

Good to keep those seeds - I always do save seeds of the 'partial victory' plants, where key traits are present just not all of them.

I feel pretty confident that you'll get your flavor with the backcross.
Granted that I haven't used backcross in this way, I have done side crosses though with non parent material, and a lot of possibilities can emerge when you stir the pot. Getting rid of undesired traits, I recall excess firmness as a dominant (likely multi locus) condition that had to be crossed down to 1/4 of parentage to an acceptable level. Likewise thinking of low sugar and low taste components as the undesired trait you want to dilute, the backcross should work, as long as there's no linkage involved.
You may still need to grow more than 2 to select the taste from F2 or F3, especially if any of the taste related components are recessive. If the space limit is fixed, you can always do time.

This first year of grow outs was mainly an experiment to see if it's possible to isolate certain micro traits. Now that I have a framework on what to select for, I have now pivoted towards flavor.

Quite a lot of micros have the excess firmness trait actually, even the parent Jochalos. I remember Micro-Tina being so firm that it never softened when turned red even after several months on the plant. The F1 of the initial cross I did stayed very firm until 2 weeks after it's turned its full color. Luckily this has been bred out in the F3 generation.

From the F1 alone, it seems that aroma compounds for Rosella are recessive, as the F1s had only a typical tomato flavor. With so many recessive traits that need to be isolated(at least 3 traits for growth habit), it becomes more statistically unlikely to get something that is ideal without the use of backcrossing.

My preference is for method B, backcrossing to Rosella several times.

Update 12/28/24:
The flower that was backcrossed with Rosella resulted in no viable seeds. In fact, none of the first 15 or so fruits of both plants had any viable seeds so far. I collected and dissected an immature fruit that was from an axillary shoot, and it looked to be developing regular sized seeds, but in extremely little numbers(4-5) for a micro(usually 10-20 seeds). This is quite strange. The flowers that developed later in the cycle exhibited high amounts of pollen production like a normal micro would. Is there a tomato trait that has low ovary viability? I should be able to save seeds from this generation, but the low possible amounts of seeds that I could initially harvest is quite disappointing.

I may need to try backcrossing again on a different flower once the plants have gone through another flowering cycle. I need to be more aggressive in the pollination for sure. While I wait several months for the backcross fruit to grow out, I could maybe use that time to grow out the thousands of F2 seeds I have saved to see if my hypothesis on early seedling traits being linked with micro traits are true. I will likely start the F2 grow outs Jan 19. In the mean time between now and that date, I will attempt to save some seeds from the F3 generation.