Micro dwarf x Indeterminate cross ideas.

[KaguyaCloud]

Update: 3/19/25


Joro F3-2 BC1 has finally germinated. The root size is as long as the indeterminate Rosella parent plant, which may be an indicator that the backcross is successful. I will check to see if there is any nyctinasty to confirm if it is the case once I plant it tomorrow. Statistically speaking, this generation should be 50% homozygous for Rosella and 50% heterozygous for both parents. This is much different from the F3 parent micro it descended from, which only was 37.5% homozygous for Rosella, 37.5% homozygous for Jochalos, and 25% heterozygous for both parents.

[KaguyaCloud]

Update 4/1/25 Joro BC1:


It's been about 12 days since I planted Joro BC1. However, I am unsure whether to update because this seedling expressed no nyctinasty after planting. It also isn't as large as the original F1 cross either despite the fact that it should have more genetics from the large indeterminate parent. So far, this plant has not displayed split branching from the either, and the leaves seem slightly rugose. I need to grow it further to see if the cross failed yet again. Luckily I crossed 2 fruits a few weeks back, so I have more insurance in case this one does not go well.

For the F2 segregation project, I found something interesting things. All the indeterminate F2s that I have grown, including the non-dwarf indeterminate, have axillary shoots that flower after 4 leaves have grown.

In another news, I have encountered an early tomato variety called "Scotia" in a discussion server. It's a normal leaf, super early determinate that is grown in Canada. And the flowering habit seems very similar to micro-dwarfs. It seems to grow 8-9 leaves before terminating immediately to 2 flower trusses.
https://www.tomatofifou.com/en/produit/scotia/

[bower]

IDK if Scotia is any earlier than the usual early red tomatoes. My friend has grown this one from time to time on her farm. They are vigorous bushes with fruit about the size of apples. About 3 ft tall under field conditions.

[KaguyaCloud]

Update 4/11/25:

Bad news. Cross failed again. This individual now known as Joro F4 has the early termination trait. However, I am currently germinating more attempted backcrosses that I have done about a month ago. Some interesting things did pop up, however.

Joro F4 does not exhibit split branching at the cotyledons, which might suggest that the trait is somewhat unstable. The leaflet pattern is 1-3-3-5-5-5.
Joro F4 grows 7 leaves before terminating to 2 flower buds just like the parent plant. The plant only has a 3 inch(7.6cm) long stem and is 4 inches(10.2cm) tall including the inflorescence. The main stem is extremely thick for a micro dwarf, it is as thick as a pencil, as shown in image 4 of the album.

[bower]

Too bad about the backcross fail, but at least there's something to be learned about the genetics/gene expression in every generation.
My hat's off to anyone who can handle those tiny flowers for crosses. Better luck next time!

[KaguyaCloud]

Update 4/19/25
F4 is growing nicely. For a compact sized plant, the flower trusses sure aren't. The plant is 3.5 inches at the internodes and the flower truss are around 3 inches tall. Such a strange, but fun size difference. It flowered 4/14/25, making it 26 days to first flower which is about average given my conditions.


F2 trials grew successfully. It was a pretty good idea to keep the F2s, as they show just how variable the dwarfing factors are despite all the individuals being indeterminate. I managed to harvest and taste some fruits from these individuals.


Joro F2 seedling 16: Non-dwarf, indeterminate. Grew extremely tall. 46 inches. Flavor is similar to the F1 parent. Sweet and okay tomato flavor.

Joro F2 seedling 7: Dwarf, indeterminate. Grew to about 22 inches. Flavor is faintly citrusy and sweet near the skin. Mainly bland however and has an off tap water after-taste. It's quite funny that this seedling grew about the same rate as seedling 12 before exploding in growth. This could be an indicator of putative mnt being only partially dominant early on.

Joro F2 seedling 12: Dwarf, indeterminate, more compact. Grew to only 8 inches tall. There is definitely another dwarfing factor that has not been characterized, likely has the putative mnt gene as it is a third of the size of Joro F2 seedling 7. The fruit flavor is excellent. Very sweet and richer in tomato flavor than the F1 parent. The tastiest individual of the F2s by far. It's rather unfortunate that it isn't determinate, but this individual is worth saving seeds for. It doesn't hurt to develop a line of flavorful micro indeterminates in the future.

Overall I'm quite happy with the F2 trials, it also shows that root size isn't really a good indicator of plant size, as seedling 16 has the smallest roots but is the tallest individual. In addition, all my current micros that I have selected for have long roots like the parent Rosella.

[bower]

Stoked to hear that you have a compact plant with excellent taste in the F2. You could have determinates further down the line, easily.

Images didn't load for me, btw. I'll check later and try again.

[Doffer]

Joro F2 seedling 12 could be heterozygous for Determineted.

[Doffer]

On this linkage map for tomato genes, the dwarf gene is located on chromosome 1. There is also a second dwarf gene on chromosome 9, perhaps this is the gene you are looking for?

https://www.mun.ca/biology/scarr/MGA2-06-17c.html

[KaguyaCloud]

Update 5/13/25


I finally have confirmed a successful cross between Joro F3-2 and Rosella, as the seedling displays nyctinasty. In addition, the cotyledons smell very similar to Rosella with a slightly chocolate-grass like scent. I have taken pictures of my pollen collecting process and will post it soon.

[Doffer]

It was quiet for a few weeks, but I’m glad there’s another update on this tomato-growing project.

[KaguyaCloud]

Here's my tutorial on collecting pollen from Rosella Cherry. I didn't want to post it until I knew for certain that this particular method I developed worked. This technique is not needed if your tomato flowers produce plenty of pollen, as you can get quite a lot from just scraping the anthers without dissecting the flower head.

It was quiet for a few weeks, but I’m glad there’s another update on this tomato-growing project.

Apologies for the delays, I didn't expect my cross to fail 3 times in a row across several flowers on the same plant, proceeded by no germination of the first seed collected from the successful backcross. Luckily I managed to germinate 2 more seeds after putting them in the freezer for around 1 week. I also started growing a few fragrant roses as another hobby.

I have just tasted Joro F4-1 generation, it is just slightly sweet and has a tiny hint of fruitiness. I think I'll name the Yellow fruiting Joro Line "Canvas" for its neutral flavor, low astringency, low acidity, branching flower trusses, and stronger style(making it much easier to emasculate). Being about 6 inches(15cm) tall, it is not as compact as its micro-dwarf ancestor Jochalos. But, I find that the more open growth habit made the tomatoes much easier to harvest. Not remarkable in terms of flavor, but very good potential to use as parental line as a nice clean slate to start with. A lot of the other micro varieties that I grew had quite a few off-flavors or are quite sour/grassy, so I think the name is fitting.

[bower]

Great name for the neutral/odd flavors. Also nice growth habit improvements for a parental line.
Having a parent that's easier to cross is a great find for micro breeding projects.
Kudos for the hard work and persistence in getting your backcross.

[KaguyaCloud]

Update 5/20/25


Another seed has sprouted. Joro BC1-1 is the one that I have taken a picture of last week 5/13/25. Joro BC1-2 sprouted and opened its cotyledons about 2-3 days after, so the growth is a tad bit behind. Compared to my Joro F1 individuals at week 1, the growth of Joro BC1-1 is about as fast.

So far the seedlings both exhibit nyctinasty, which would indicate that this trait is dominant. But this is a great way to determine if a cross is successful at the cotyledon stage. I cannot tell the leaflet pattern of these individuals just yet, will need more time to tell.

[KaguyaCloud]

Update 5/25/25


Some interesting new discoveries from the backcrossed generation Joro BC1.

Joro BC1-1: Regular leaf. Terminated after 3 leaves have grown with no flower truss, new axillary shoots growing from cotyledons and from the 3 leaves of the main stem.
Joro BC1-2: Regular leaf. Also terminated after 3 leaves have grown with no flower truss, new axillary shoot growing from the center of the plant.

To my surprise, it seems that the "twin stemming" phenotype(where the stem terminates after 0-3 leaves then grows 2 or more main branches) continues to show up even after the backcross for the two individuals that I have sprouted. In addition, this trait might be dominant. Weirdly enough, the F1 generation didn't seem to express this trait, which may suggest that there is a level of masking of this phenotype or a combination that is required for it to appear. My accidental Joro F4 seemed to have expressed no twin stemming trait at all, which suggests that my current breeding line seems to still be heterozygous in the twin stemming phenotype.

I hypothesize that the micro-dwarf Jochalos contains perhaps several normal single stemming genes and that Rosella Cherry contains the multi-stemming trait. Based off of my F2 trials, twin stemming can occur in regular leaf non-dwarf individuals. Considering the fact that my BC1 generation is either homozygous or heterozygous for Rosella Cherry, this might be a strong indication that the genes responsible for branched stemming comes from the indeterminate parent. There's not enough information to know for sure what combination of traits is required, but I'm happy to create a distinct, genetically stable line of early branching micros. One more set of backcrossing from the F2s or F3s of this cross should confirm my suspicions.

In other news, I think I have bred out one of the micro-dwarf traits, specifically the reduced leaflet trait. After studying the axillary shoots of my F2s through F4s, the expression is 3-5-5 instead of 1-3-3. Not entirely a deal breaker since the growth habit is still quite compact with the early termination gene to 2 flower truss trait(which I think is an extreme variation of the sp gene).

[Doffer]

Could the twin stemming be caused by environmental factors? Perhaps additional light (lux) or proximity to the LED is contributing to it?

[KaguyaCloud]

Could the twin stemming be caused by environmental factors? Perhaps additional light (lux) or proximity to the LED is contributing to it?

Environmental conditions are relatively constant in terms of light intensity and proximity to the LEDs of the breeding line I'm working with, but I can't rule that out as you said. I could try light intensity experiments once I've stabilized the genetics.

[bower]

Just about all of the specific growth habit traits seem to be subject to variation by environment. But it is interesting to pursue these details, which seem very relevant to the indoor growing context and its less variable conditions.
One day, you will have to do a large, really large growout to find the evidence for a genetic mechanism that is stronger than environment.

[KaguyaCloud]

Update 5/27/25


Quick update, it's been 2 weeks since the Joro BC1 generation were planted. They are developing quite nicely. Being 75% Rosella really influenced leaf development compared to my F1s(you can see them in post #92 here: viewtopic.php?t=4909&start=80#p117563).

Joro BC1-1: 4 inches(10cm) tall with a comically long 9 inch(23cm) third leaf. Leaflets are in a 1-5-7 pattern and are extremely wispy like Rosella. Compared to the height of the F1, it's around the same height. I don't think measuring the height might be accurate in this situation, mostly because the "true" 2 primary meristems are growing from the axillary portion of the third leaf.

Joro BC1-2: About 3 inches(8cm) tall. The leaves of this individual are also quite wispy.

[bower]

I'm not seeing the pics, and getting a blank screen at Imgur too.
Edited to add - how strange, the moment I posted the images popped up after all!