Micro dwarf x Indeterminate cross ideas.

[KaguyaCloud]

Update: 10/4/24
The red F2 is not great tasting. There are some that were sweet, but they mostly had the typical bland micro flavor to them. I have gathered enough seeds from the pale F2(around 80) and am starting to germinate the F3 generation to see if the dwarfing traits are stable. I'm starting off with 3 seeds. If flavor improves, stays consistent, or decreases, it'll let me determine whether or not this line is worth refining.

In addition, I have propagated a cutting of the pale F2 so that it can be crossed back with Rosella to restore some flavor and sweetness genetics. De-masculating the flowers of the pale F2 is slightly easier due to the pistil being less delicate, but it's still quite hard to do.

I currently have a "legacy stock" of my breeding project consisting of Rosella, Joro F1, and the Joro Pale F2 cuttings that are in a separate shelf. They are in their own labelled 4 inch pots and I occasionally prune back the indeterminates to maintain a small size.

[KaguyaCloud]

Update 10/13/24:


After further analysis of the shoot architecture of the Pale/White fruiting Joro F2 plant, there's a lot of interesting growing patterns. Micros, from what I've observed, skip the vegetative phase of all of their axillary shoots. This means that their axillary shoots/suckers immediately grow 3 leaves and a flower truss instead of growing 7-14 leaves followed by a flower truss.

As we know from the previous observations, the pale F2 immediately terminated after 2 true leaves have grown with no flower truss. However, the stem and leaves that grew before terminating seem to only produce primary micro-dwarf shoots instead of the regular micro axillary shoots. Those primary micro shoots then only produce micro axillary shoots, which is quite strange. The diagram I have made shows only two shoots, but there are at least 4 primary shoots that have grown on the actual plant.

This may suggest that there is a gene that suppresses the vegetative phase of the axillary shoots, which for some reason was not fully suppressed in the first two leaves of the F2. How strange, it may be possible that this vegetative phase suppression may be incompletely dominant in the presence of another gene(determinate?). This whole ordeal makes the early termination point of the seedlings even more suspicious, as some kind of conflict in the genetics or development happened during stem development as it grew.

[KaguyaCloud]

Update 10/22/24:


The F3 generation from the pale fruited F2 has finally sprouted. It seems that the seeds require around 24 hours in the freezer to sprout, which is a trait in the parent plant Rosella Cherry. First F3 seed that developed cotyledons exhibited long roots like normal sized tomato seedlings, which is not common in the micro dwarfs I have worked with. However, the cotyledons have not closed during the night cycle, which would indicate that there is a dwarf gene present. The second F3 seed that is in the process of germinating does have the smaller and characteristic hook shaped in the root system that is present in micros.

I have also included a picture of my legacy stock from this breeding project. At the moment it is quite easy to keep them alive and growing within the constraints of a 4 inch pot. Over time I hope I can fill the shelf up with the whole line of successive improvements. Backcrossing has been largely unsuccessful to perform on the pale F2, Rosella Cherry does not develop that much pollen from its flowers.

This marks almost a year since I've started the project(November 18) and I have pretty much grown about 4 successive generations(1 generation of parents, then 3 hybrid generations) at an extremely leisurely pace. Assuming I keep going, I should be able to get to the F7-8 by next year if I am able to figure out how to keep the flavor consistent. I will focus mainly on isolating the dwarf and early termination gene with flavor for the time being.

[bower]

My hat's off to anyone who can do crosses with those tiny micro flowers.
WRT pollen production, in my greenhouse situation there are very definite times of day to get pollen easily. Late morning to mid afternoon seems to be the window of opportunity, and a waste of time to try getting pollen earlier or later in the day.
YMMV in the indoor grow where light is constant, but worth a try.
Another thing about pollen, not every open flower is as ready and mature as another. I always try to collect pollen from more than one blossom on any given day. This means different stages of pollen maturity are present. Also I repeat apply pollen usually for three days, to make sure the mother part is also receiving pollen at the ideal stage of maturity.

[AKgardener]

Keep up the good work!!!

[KaguyaCloud]

Update 10/28/24:
https://imgur.com/a/joro-f3-update-Ghg8i7H
Out of the 3 seeds that were in the germination chamber, all of them at the very least sprouted roots.

Seedling Joro F3-1: Long roots. Stem before the cotyledons exhibit a dark color. No true leaves after the cotyledons, immediate jump to growing 2 axillary shoots. Although, these axillary shoots are possibly main shoots judging by the parent's morphology. I suspect that they will terminate to 2 flower trusses after a set number of leaves.

Seedling Joro F3-2: Abnormal seedling development. Small root size similar to micro-dwarfs. Stems before cotyledons are green. One cotyledon is very diminutive and the other cotyledon has 3 pointed ends. No sign of true leaves yet. Abnormal cotyledon shapes did occur during F2 selections, but none of the seedlings with the dwarf gene exhibited this trait.

Seedling Joro F3-3: Germinated. Extremely small root mass. No signs of leaf development yet.

Twin axillary stemming seems to be a heritable trait, which is quite interesting. I wonder if one of the genes responsible for micro-dwarfs involve termination of the main stem after the cotyledons, and maybe the leaf reduction gene causes the number of axillary shoots to grow to be reduced to 1 axillary shoot. It looks like longer roots could possibly be a recessive trait? Currently there are more seedlings with reduced root masses than long root masses during germination, could be a coincidence due to low sample size however.

[KaguyaCloud]

Update 11/8/24:


Joro F3-1: Flower buds visible on 11/7/24, making it approximately 16 days since open cotyledons. Leaves to first flower seems to be about 7 leaves, following a 3-3-5-5-5 leaflet pattern. Too early to see if the early termination gene is preserved, but I am hopeful.

Joro F3-2: Planted 10/28/24. Extremely stunted seedling despite abundant nutrient and light levels, tiny cotyledons(half to a third of the size of a micro cotyledon) and likely would have not grown if I did not cut the seed coat off. Leaves grow in a 1-3-3-5 pattern. I wonder if small root size is linked to reduced leaflet patterns. No sign of flower buds yet, it may take another week or so.

Joro F3-3: Did not germinate successfully. Unable to properly form any cotyledons.

Twin stems seem to be a very unique trait that my breeding project has produced, and it is consistent as well. However, this does lead to a lag time as the seedling takes a few days longer to form double the number of leaves and shoots of two stems. Crossing my fingers on flavor.

I am performing my third cross pollination attempt of the Pale Joro F2 and Rosella. Flavorwise, it seems that the Joro F2 cutting that I have saved has a very nice flavor when there is adequate nutrient levels in the leachate(700-1400ppm). Joro F2 remains parthenocarpic in its fruit set with low pollen yield. Weirdly, the plant has started to produce fruit with slightly pointed ends. If the de-masculated flowers bear any fruit, then I could determine how consistent the traits are in back cross generation 1(Joro BC1).

[KaguyaCloud]

Update 11/10/24

Joro F3-2 has flower buds despite the size. When I looked back on my records on the micro parent Jochalos, it seems that this Joro F3-2 actually exhibits about the same size diameter as the parent at this growth stage. In addition, it has the 1-3-3-5 leaflet growth pattern like the micro parent. Comparing F3-1 with F3-2(small), it seems that the leaf reduction trait further halves the size of the plant. It's possible that F3-1 is homozygous for no leaflet reduction or heterozygous for the leaf reduction trait.

Micro seedlings in a germination chamber exhibit extremely small root mass growth compared to regular varieties. If the stunted plant size is linked to small root size, then it's possible that micro traits can be selected for at the F2 level(small root size, cotyledons remain open during the night cycle). I hypothesize that this reduced root size may be linked to leaf reduction, which would make sense since smaller root masses typically lead to smaller plant sizes.

[bower]

Interesting ... you could grow your F2 in transparent containers (or even hydroponically) to easily distinguish the smaller root mass.

[KaguyaCloud]

Interesting ... you could grow your F2 in transparent containers (or even hydroponically) to easily distinguish the smaller root mass.

Actually, it may not be necessary, as you can see this in the germination stage. The smaller root mass of F3-2 is very distinguishable compared to F3-1. Usually regular tomato plants will exhibit the normal longer root as shown on the left. Looking at my July 3 post, it looks like shorter roots appear in 4 of the 20 seedlings that I have germinated, which is very close to a 1:4 ratio.

https://imgur.com/gallery/joro-f3-updat ... 24-fdE09zh

[Doffer]

It would be great if you could develop a selection method to select microdwarfs in the F2 generation as seedlings. Especially since the probability with 4 genes comes down to 1/256.

[KaguyaCloud]

It would be great if you could develop a selection method to select microdwarfs in the F2 generation as seedlings. Especially since the probability with 4 genes comes down to 1/256.

Here would be my method of selecting for the dwarf and leaf reduction traits:
1. In a tupperware container, place a folded paper towel inside.
2. Add filtered water until the paper towel is saturated with small amounts of water around it. Then place a sheet of copy paper on top of the wet paper towel, this is to prevent the roots from growing and sticking into the paper towel.
3. Add the seeds, space them out evenly, around 2.5cm or 1 inch apart. Put the lid on top of the container.
4. Place the germination chamber under grow lights that are around 40,000 lux from the top of the tupperware.
5. Note down short root seedlings from longer root seedlings.
6. Once the cotyledons have opened up in the chamber, transfer to a 70/30 coconut coir perlite mix that has been hydrated with a dilute hydroponic fertilizer. Make sure to segregate the short root seedlings from the long root seedlings.
7. Monitor the seedlings during the night cycle for several days. Cull any seedlings that close their cotyledons during the night cycle. Any seedlings now should have the dwarf(d) trait. If the seedling also has short roots, it should have the recessive trait that leads to the leaflet reduction trait.
8. All seedlings from here should have the dwarf trait and some will have the leaflet reduction trait. All that is left is selecting towards the determinate and early flowering traits.
9. Flowering pattern traits should be visible at week 3-4. Any seedlings with sympodial repeats after the first flower truss will either not have the early termination gene or be heterozygous for the early termination gene.

Right now, I think that the pale F2 that I have selected has: dwarf(homozygous), early flowering(homozygous), and leaflet reduction(heterozygous). The dwarf gene(d) alone doesn't seem to influence root length during the germination stage, even when heterozygous with the small root trait. I still do not know if the determinate gene is linked in any way to the early flowering gene. It should be statistically unlikely for me to isolate this many recessive traits with so little attempts.

Regardless, I am breeding micros for flavor as the top priority. If a certain micro trait gives inferior flavor, I will select it out, but I do find value in keeping and segregating out those specific micro traits.

[KaguyaCloud]

Update 11/16/24


The traits that are segregating further are really interesting. It looks like the early stem termination gene is a stable recessive trait, as both F3 plants immediately terminate to 2 flower trusses with no sympodial shoots just like the parent F2.

Joro F3-1: Elongated, wispy leaves like Rosella and its F2 parent. Longer internodes than F3-2. 7 leaves to first flower. Branching flower trusses. Regular size flower truss. Expression is very similar to the Pale Joro F2 plant.

Joro F3-2: Very fast growing, caught up to size. Compact and reduced leaves, which are reminiscent to the parent micro Jochalos and the red fruited indeterminate F2. Both stems have 6 leaves to first flower, making it the earliest cultivar yet. One stem has a leaf growing from the truss, like the F1. Flowers are as large as the flowers of Rosella Cherry, which is the largest flowers I've seen in my breeding project to date.

I believe that Joro F3-2 is the first true plant that has all the major micro traits that I have described(Dwarf, early termination, leaf reduction). This might also suggest that small roots may be linked to reduced leaves with a smaller growing habit, which could be useful for any future micro breeding projects that involve crossing a micro with an indeterminate. I think I will keep this one as a foundational breeding stock for preserving micro traits.

It seems that the internodes and leaves are not as compact as the parent micro plant Jochalos, which leads me to believe that there may be even more traits that reduce plant size. That being said, I think I am fine with the size that I currently have, at it is compact enough to manage in the small growing space that they are in. Now I can focus on selecting for flavor.

[Doffer]

If Jora F3-2 possesses all the microgenes and the taste of the fruit is not as expected, I would cross it back to Rosella.

[KaguyaCloud]

For sure, I will do attempts of backcrossing with Joro F3-2 to see if I can isolate the traits easily. Since dwarf and the leaflet reduction gene could be found at the seedling stage, it should now be a 1 in 16 chance of getting a determinate and early flowering trait.

[KaguyaCloud]

Update: 11/21/24


Joro F3 plants are flowering profusely just like the Pale F2 parent. A new trait has popped up out of nowhere. It looks like both of these F3 plants have splits in their stamens, leading the pistil to be exposed out a little. If this trait is stable, it might actually make it easier for people to cross pollinate due to most micro dwarfs having extremely delicate flowers. However, this might make seed saving more problematic, as less potential for pollen to hit the stamen might equate to less seeds. If there's parthenocarpy, then it might not be too much of an issue when worrying about fruit set. Seedy fruit isn't entirely desirable anyways.

F3-2 also has extremely long sepals in relation to the flower size, which I find interesting. This might strike out sepal length as a potential link to the micro size.

[bower]

Those plants are fantastically cute!! So tiny with flowers, I am impressed.

The flower condition known as 'exserted stigma' does in fact reduce pollination and fruit set. Breeders who are working to develop non-selfing, strictly outcrossing tomatoes are selecting for the trait. This is a bit complicated because aside from genetics of flower structure, environmental conditions can also cause it.
Breeders who are selecting for high production tomatoes do select away from exsertion as well, to ensure self-pollination and fruit set is maximized. There are a few published articles out there, which documented the effects of exsertion on cropping ability.

[KaguyaCloud]

I do see quite the reduced fruit set in the Pale F2 compared to the indeterminate F2 that I culled. Although, it might be because having so many flowers creates a high demand for nutrients that I wasn't able to provide.

And on top of having exserted/exposed stigmas, I noticed that the amount of pollen that is produced is significantly less than regular tomato plants. Usually, when I shook the flowers, I could see tiny dusts of pollen floating down. But in Rosella, Pale F2, and all F3s, I did not see a single spec. Yet, there's still quite a good number of seeds in them.

I heard that breeders also seem to like the parthenocarpy trait in tomatoes as well as that also improves fruit set. I just noticed that some flowers have already began to set fruit despite not fully opening in F3-1.

[KaguyaCloud]

Those plants are fantastically cute!! So tiny with flowers, I am impressed.

For reference, here's F3-1 right next to a standard 12oz(350mL) US cup.

[bower]

Fruit set is a multi factor question for sure. Vigor and fruit set often go together, and nutrients, light, temperature conditions play a big environmental role in the uncontrolled setting.
Flower structure and probably the cues to release and shed pollen are controlled by a number of genes. Personally I select for plants that readily self pollinate without being shaken or etc. because getting a good crop with less effort is a key goal for us. But I do not know what genes are coming together to make that happen.
Another thing that affects fruit set is the balance between vegetative vs reproductive growth - low light for example pushes vegetative growth, and plant response to that is genetically variable. But this obviously isn't the case with your tiny flower covered plants!
I had a plant this season that produced lots of flowers and barely any sets. It did produce a bunch right at the end of season after I cut it back and tied it up. Tomatoes seem to sense very well whether they are strong enough or well supported enough to carry fruit weight. Some growers have a routine of providing support to the trusses, to encourage a heavier set.
OTOH my plant didn't seem to produce much pollen either, as I discovered when I was making a few crosses. It took pollen readily when provided, and set up those. So there may be pollen defects lurking in the genomes of some tomatoes. Or it could be structural combinations of traits in the flower, that don't allow the pollen to effectively be released or to get where it needed to be.
You might dissect a flower and compare to flowers of the parent lines. Micro flowers are so tiny, they have for sure their own set of flower structure genes, and maybe some combination of the divergent parent traits is less functional.
Edited to add: great pic with the cup. I can see the truss architecture where there's a stem with unflowered buds. I would imagine that this stem thickens up quite a bit by the time you have fruit on it - this is a variable trait and some plants don't crop as well at the same time they have thinner stems ie maybe insufficient support for a full truss of fruit. Something to keep an eye on.

I don't have the scoop on parthenocarpy genetics, haven't read about it. Parthenocarpy turns up in a few OP's, but the fruit tend to be smaller, or in some cases really miniature. It's been a while since I grew Siletz and Cold Set, but IIRC with Siletz in particular there were no clues like size or shape to tell you whether there'd be any seeds or not. I picked fruit after fruit planning to get seeds and there were lots of full sized fruit with no seeds at all. So there's something special about those deliberately bred parthenocarpic varieties that maintains the size when seedless.