Update: 3/30/24

It has been 5 weeks since I have grown my Joro F1. It is now around 80cm tall.
I do not think it is practical to measure height anymore at this point, as the lack of light hitting the top of the main stem is causing the internodes to lengthen considerably.

The Joro F1 propagation experiment has also been a success. I have picked an axillary branch that just started growing flower buds, took off the first 2 leaves, then buried the cutting up to the third leaf. Growth was paused for the first week or so with dying leaves, then the cutting began to bounce back as it started to root into the soil. It has been approximately 13 days since I have planted the cutting and it has already flowered at around day 12. Overall a very promising outlook on growing the F1.

Update: 4/16/24

It seemed that the F1 Joro seems to be on track. I had to prune back quite a lot of growth as it was sprawling too many side shoots. After 51 days since planting, the F1 hybrid plant on the right started to reach the breaker stage of the ripening process. I should expect the first trusses to begin at the breaker stage in another 4-5 days. Despite the earliness in flowering, it seems to takes longer to ripen overall. Based off my estimates of time from flower to ripe fruit, the tomatoes should have turned red by now, but haven't.

I've noticed that the fruit shape is more akin to the Micro Dwarf parent Jochalos, as the fruit shape is more wide than it is tall compared to the more spherical shaped Rosella Cherry. The breaker stage is also more orange than Rosella Cherry as Rosella Cherry's breaker stage is a peach color rather than neon orange. The F1 also is not prone to create more axillary shoots after the first one in the same area is cut off like Rosella Cherry.

I am also thinking of having a new method of F1 vine management within a confined space. For example: I could prune a single vine(V1) and then cut the growing tip off once it reaches the end of the 2ft grow lights, but allow one axillary shoot(V2) to grow.

Once the fruit in V1 begin to ripen, I can grow V2. Once all the tomatoes in V1 are ripe, I can cut V1 off, which would allow V2 to grow. Then from V2, I can train the axillary shoot that grows(V3) from that vine. But the timing has to be better, as the rapid amount of growth that I could lead to too many branches. With this method, I could avoid needing to coil the stem around the plant after it reaches the end of one of the grow lights.

Beautiful ripe fruit.
Just aside from the effects of growing conditions, some long term growers have suggested that tastier fruit have longer ripening times (from blush to ripe). Possibly a consolation for waiting...

If u grow the F1 for food u can use the V1 and V2 method. But if u grow the F1 for seed production, u can cut green fruit and ripen it on a different warm place.

I notice that fruit with blossem end rot matures early and the seeds germinate very well. So maybe this can speed youre breeding?

Did u think about extra CO2 ppm for faster growth?

Doffer wrote: ↑Wed Apr 17, 2024 12:53 pm I notice that fruit with blossem end rot matures early and the seeds germinate very well. So maybe this can speed youre breeding?

Did u think about extra CO2 ppm for faster growth?

There are several traits I’m watching out for in fruit development. Rosella cherry isn’t fully ripe when it turns to it’s final color. Instead, for some reason, it is fully ripened after it can easily detach from the sepal on the vine.

Rosella Cherry unfortunately has a very long germination time(2 weeks) when only drying the seeds. Fermentation or vernalization may be necessary to get rid of the potential excess germination inhibiting hormone in the F1.

CO2 supplementation does promote more photosynthesis. However, this is only the case if nutrient management and light is managed very well. For example, there’s not enough nutrients in soil, then the plants will very quickly show signs of nutrient deficiency. Personally, I do not do it for convenience reasons.

Update 4/19/24:


First fruit in the F1 Joro has finally turned red. I am unsure if it is fully ripe, however. I will likely wait around 2 weeks to see if the fruit will be very loose from the plant.

The Joro plants sprouted at 2/23/24. This would mean that it has been approximately 56 days since the cotyledons emerged from the soil, which is the fastest I've ever grown any tomato so far.

56 days is amazing - but I generally count mine from seedling emergence to first blush. So even shorter than that!

Here a paper about speedbreeding tomatoes.

If u keep seedlings for 8 days at 14C u get 3 days early fruit.
Also a big container speed up the process.

Strange they did not pay attention to light in combination with temperature.

https://www.sciencedirect.com/science/a ... via%3Dihub

I forgot to do an update several days ago:
4/21/24:

First ripe fruit that easily popped off of the vine were collected.

It seems that being heterozygous for multiple locule number still gives a chance for it to express 3 locules when crossed with a two locule fruiting tomato.

The darker skin color from Rosella Cherry seems to be a recessive trait, as the tomatoes in the F1 have skins that are practically identical in color to a regular red tomato. This is not the anthocyanin trait as far as I am aware of, but something very different. Here's an image comparing Rosella Cherry and Micro Tina. The flesh in both are also similar in hue to their skins as well. Not sure what the genetics are for this trait.


The gel color in the F1 is yellow when very ripe and green when slightly ripe. Rosella's gel color is green all the way through, while Jochalos is the standard yellow.

Comments on taste: Standard store-bought tomato flavor with a little sweetness and a good slight tang. Honestly I was both surprised and disappointed that it tastes so dissimilar to either of the parents. Sweetness may not be surprising as it tastes intermediate of the parents(one sour one sweet). No fruity or citrusy aromas or aftertaste. I will likely need to perform a backcross with the F2 generation depending on how the further generation goes. But I am quite curious to see the results.

Looks like Rosella cherry is a gf/gf pink.
My Skipper Pink cherry is similar.
IDK why these lines ripen to a dark pink instead of looking more like a 'purple' black.

@Doffer tx for posting that article - very interesting. I might try some of these tricks to get earlier maturity for my late starts this season, if I can. I was hoping they would just grow faster anyway due to being longer days and warmer temperatures.

Update 5/4/24:
More updates on the Joro F1. It seems that the fruits I picked initially were actually quite under-ripe. After letting the fruits sit on the plant for a whole 2 weeks after they have turned fully red, they've developed a pleasant generic sweet cherry tomato flavor. Locule number seem to be between 2-3 based off the fruit cross section, but it is mostly 2 locules from what I have seen so far.

I honestly wouldn't mind propagating and growing the F1 for a while. I still need quite a lot of seeds considering a large potential number of genes that need to be isolated. I think the plan for now is the harvest as many seeds as possible. Right now the odds are against me, as I need to select for:
1) Leaf reduction(recessive)
2) Dwarf gene(recessive)
3) Early flower termination(recessive, may require dwarf and determinate gene to function)
4) Determinate(recessive)
5) Fruity/Sweet flavor

It seems that the micro-dwarf genes are all indeed recessive, as the only phenotype I've observed coming from the micro-dwarf parent plant is a compact truss size. I'm crossing my fingers that the truss size is linked to one of the micro dwarf traits. If I desire purely just to select for the Micro-Tom phenotype, I have a 1 in 256 chance if we were to assume that there are 4 non-linked genes required for the micro trait.

Based off my estimates from my first 2 fruits, there should be on average 37 seeds per fruit. Since I harvested 10 fruits so far, that would be around 370 seeds. I only have a chance of obtaining 1 micro plant, worst case scenario. It will take some time to harvest a good number of seeds, maybe around 2000. I have around 60 fruits at varying stages of ripeness spread across 3 plants at the moment. This would mean that I have enough for around 2,220 seeds, which is enough for 8 possible micro dwarf plants.

In the mean time, I could probably start planting the F2 generation after 2 weeks. After meticulously rinsing and scraping the gel off the seeds, I will let it dry for 1 week and then place it in the freezer for another week. Afterwards, I will thaw the seeds and place them in a germination chamber. I have enough space to use 20, 4 inch pots. In each pot, I will only put 4 seedlings. This totals to around 80 plants to grow at a time.

Selection for the seedlings will be based off of leaflet number, keeping only those a 1, 3, 3, 5, 5 leaflet pattern. This process should take 2 weeks for every batch of F2 plants, which means that I should be able to ideally obtain a micro phenotype after 6-12 weeks of selection. I will likely track to seedling phenotypes(not closing during night, hypocotyl length, coloration) to see if any are linked to the dwarf traits.

Just for insurance i would grow a Mirco tom with youre F2 generation so u can make a back cross if u do not find the 1 oud of 256 plants is micro dwarf.

Update 6/3/23:

So far I have yet to start on the seedlings yet. Life's been a little busy at the moment. However I just now realize several key things while growing the F1.

The cutting I have made of the Joro F1 produced the absolutely tastiest, sweetest tomatoes I have ever eaten in my entire life. Practically no acid. The flavor is like a typical grape tomato, but the amount of sweetness is comparable to a very sweet orange or a syrup. It also has a very faint musky after-taste similar to the micro parent Jochalos.

It turns out that trellising the plant horizontally with 3 12W 2ft grow lights at 40,000 lux and using a 24 x 6 inch container for one plant produced exceptional quality fruit. Waiting until they basically fall off the plant(2-3 weeks after turning fully red) is a sign that a truss of fruits is ready. The ones in smaller 4 inch containers produce sweet fruits as well, however there is a slight off flavor to them that is astringent/grassy.

I have decided to continue to propagate the Joro F1 as both a genetic stock and as an occasional light snack. But I'm floored that I created something so sweet tasting. I'm really hoping that the F2 will be just as good, and will begin my seedling planting in the next few weeks. I think I have collected enough to get at least one micro trait. If not, that's okay.

Additive QTL's such as for sweetness can produce astounding results if your parents happen to have different high value alleles, at different loci, I guess? Since there are generally multiple QTL's involved.
Glad to hear you were lucky with that, and hey! Growing and eating the delicious fruit, definitely a worthy use of your light space.

Looking forward to hear about your F2's. Not at all impossible you'll find something even sweeter.

I was thinking most sweetness genes are recessive, so in F2 u can find even sweeter fruit.

I have compiled an excel sheet with of 26 traits of varying dominance that I could isolate in the F3 and further generations. It could be used to check how much of the indeterminate genes can be conserved with the micro dwarf growth habit. I'm curious to know if these findings correlate with anyone else's breeding experiments.

When referring to the green gel trait, I am stating that the gel still remains green even after the skin has turned brick red. The heterozygous F1 usually takes another 2-3 weeks before the green gel turns to a clear orange color, which is actually an excellent indicator of ripe/sweet fruit for this F1. This is quite strange considering that the green flesh seems to be recessive, but green gel is not fully recessive.

I also omitted fruit size due to variability of the containers, but the F1 fruits are typically 1.5 inches in diameter(similar to Rosella Cherry) compared to the 0.5-1 inch diameter fruits of the micro dwarf parent. It's still uncertain if the dwarfing genes fully influence fruit size or not, but that can be determined later down the line.

One strange trait that I've noticed is that the F1 also has a very small percent chance to grow a leaf in the flower truss, which neither of the parents express. I've only seen it happen 2-3 times, so I'm unsure if this is an environmental or genetic thing.

Update 7/3/24:


The F2 seedlings seem healthy. I have sowed them 6/28/24 and 90% of them seem to have already germinated.

The very distinct corkscrew root gene from Jochalos has reappeared yet again in the F2 with quite a range of variation. From what I remember, most tomatoes usually grow relatively straight roots after germination. Either way, I will likely plant them and cull them after the first 2 leaves have grown. The plan is the germinate 20 seeds at a time to pace myself.

From what I've observed in the past, the root zone in micro tomatoes are relatively smaller compared to the indeterminate Rosella Cherry(can grow up to 3 inch long roots at the cotyledon stage). I wonder if dwarf segregation can occur at this stage.

Update 7/6/24:
Joro F2 seems to have rooted quite well in the media.


I have circled the 2 seedlings that aren't closing during the night cycle. They are a tad bit shorter than the others, but one of the main differences I noticed was that their cotyledons are slightly more curved upwards. In addition, there are some mutant seedlings with notched tips that are actually cotyledons that branched in a Y pattern! I wonder if that's just a developmental defect.

The leaflets of the majority of the cotyledons exhibit the chocolate scent from Rosella, which likely means that there is some intermixing of the genes at least for the theoretically dwarf seedlings. Whether or not they'll segregate with the other dwarf genes will be a good question. I will still continue to look through reduced leaflet count to see if that is a recessive trait that requires multiple genes to be expressed.

Update 7/10/24:
Had a power outage for 2 days. Was not able to update on the progress of the seedlings. But now since the power has been back, it seems very apparent on which seedlings have the dwarf gene. There's quite a large variation in height of the seedlings, which may suggest that the genetics is pretty variable.

The tallest seedling was around 3 inches while the smallest seedlings have 1 inch long stems. I rotated the pots from one end to the other so that the light amount is relatively even over the course of 4 consecutive days. Overall, I think I am going to make a decision to cull the non-dwarf tomato plants.

I can now confirm that the 2 seedlings that do not close during the night cycle are considerably shorter than the seedlings that do not. There are some incidences where the taller seedlings have 1 leaflet as their first true leaf, but it's likely they may not have the dwarf gene based on personal experience growing micro-dwarf varieties. I would need to sprout more seedlings to determine if there's a consistency in the pattern. Either way, the results are promising.



Do we know if determinate seedlings are shorter compared to their indeterminate counterparts? I have yet to grow a determinate plant myself. I am questioning because the micro-tom phenotype shouldn't have appeared this early according to the potential number of independent genes that have to be intermixed together at the seedling stage(dwarf, determinate, leaf reduction). It's too early to say until they grow out their 5th true leaf.

The answer to that question is no.
In growing out crosses between indeterminates and determinates, it is impossible to tell one from the other until after they have flowered and shown the determinate cluster pattern.
In some cases I had seedlings that appeared indeterminate for 6 or 7 cluster patterns on the main leader, and only terminated as a determinate pattern quite late in the game.