Micro dwarf x Indeterminate cross ideas.

[KaguyaCloud]

Oh its no problem, I'm just so surprised that after so many years that no one has really fully characterized what makes micro-dwarf tomatoes so small. I guess for my experiments, I'm actually trending towards the opposite spectrum of size compared to you. I am strongly selecting towards a taste, size, and flowering behavior that is similar to Micro-Tom due to space constraints. I've already broken down the plan into phases.

Phase 1: Grow the parent plants and cross. So far, my main plan is to cross Rosella Cherry(early indeterminate) with either Jochalos or Vilma. Record down how many leaves each variety produces before forming a flower truss. See if I can stunt indeterminate plants indoors so that they don't run wild.

Phase 2: Grow and study the F1 to determine which traits from each parent may be dominant or recessive. Cross F1 back with the micro dwarf parent to produce a back cross generation.
Based off a study on Micro Tom x M82(determinate non-dwarf), it seems that the number of leaves a tomato produces before flowering in the F1 is between the micro dwarf and M82: https://www.plantbreedbio.org/journal/v ... &&vmd=Full

Phase 3: Grow and select Back Cross Gen 1(BCG1) and select for size. If there are 3-4 recessive genes that theoretically need to be selected(sp, d, mnt, mnt2), then I will see a spectrum of only 16 distinct phenotypes. However, since I want to prioritize determinate growth and the dwarf gene, I will cull every seedling that isn't growing rugose leaves. Ideally I plan on keeping only 4 of the 16 phenotypes(ones with at least sp and d). In the end, I plan on growing 8-10 plants in total exhibiting rugose leaves and hopefully determinate growing habits. Statistically speaking, there should be 1-2 plants that should exhibit the phenotype of the parent plant. This would mean that I should prepare approximately 32-40 seedlings to start with. Continue growing out BCG1 until a single plant or several plants exhibit the phenotype of the micro parent. Make sure to grow a micro dwarf as a control next to BCG1 for a baseline growth habit.

Phase 4: If general growth habit is some-what established, select for flavor. If the flavor is too similar to the original micro parent in all of BCG1, cross BCG1 to the F1 hybrid to produce BCG2 to increase the percent of genes belonging to the indeterminate parent and repeat the process of phase 3 again.

Phase 5: Select dominance in growing behavior(flower when 5-6 leaf nodes). Self the individuals of the backcrossed generation and select the best seeds for flavor for the next 6 generations. After that, I have no clue on what to do if I actually create a new tomato variety.

With my indoor growing conditions, I can grow a single generation of micro dwarf tomatoes in about 65-75 days. Phase 1-2 will take me approximately 150 days. Phase 3-4 will, worst case scenario, take another 150 days or more. Phase 5 will take 450 days assuming that I am able to self and select the seeds. So this is about a 2 year long project in ideal conditions.

[KaguyaCloud]

After some further research on leaf structure. I've grabbed data on 45 varieties in renaissancefarms.org and compared the leaf shape to height. It seems that after ordering the varieties by height, it seems that the shortest micro tomatoes mostly exhibit 5 leaflets per leaf instead of the classic regular leaf pattern that tomatoes have. This might be due to those specific varieties still having the mnt mutation, while others were bred out.


Here's a research article on genetically modifying and fixing the BR-deficient gene in the Micro Tom variety:
https://www.researchgate.net/publicatio ... ileContent

[KaguyaCloud]

Update 12/9/23:

It seems that I was a little too successful growing the parent indeterminate plant Rosella Cherry inside of a 6 inch pot. It's not even been a 3 weeks just yet and it has already began to grow flower buds. The plant itself is 10 inches tall. I will likely have to top it off right after the first cluster of flowers so that it does not become a monstrously sized plant. Nutrient ppm consistently reads between 450-800ppm.
This is good news. It means that I can likely scale down the size of the plant into an even further in a smaller pot. I really want to propagate the currently Rosella tomato into a tinier pot size so that it is more manageable.



According to this study:
https://www.publish.csiro.au/fp/pdf/FP12049
Doubling pot volume increases plant biomass by 43%. A standard 6 inch pot is 1L in volume. A 4 inch pot is about 0.5L, so I should be able to reduce biomass and overall size by 43% by halving it(And hopefully growing only a 4.3 inch tall plant).

[KaguyaCloud]

Update 12/22/23:

I have found quite a few interesting things morphologically speaking on the leaves and growth behavior of Rosella Cherry(normal indet.), Vilma, and Jochalos tomatoes. I began growing Micro Tina, as it is very much related to the original Micro Tom strain.

First thing: The number of leaves that grow in determinate micro tomatoes do not determine size or maturation time. Jochalos developed 9 leaves before terminating at two flower stalks while Vilma developed 8 leaves before terminating at two flower stalks. All varieties(including regular indeterminate Rosella Cherry) developed flower buds at around 20 days of growth when grown with around 29 DLI and ample nutrients. Jochalos, while having more leaves, is still shorter and smaller in growth stature.

Second thing: Bigger micro tomatoes grow more primary leaflets on each leaf compared to smaller micro tomatoes. When grown in the same light levels of around 40,000 lux, the following varieties develop these of the following primary leaflet patterns in each leaf after the cotyledons have grown:

Rosella Cherry: 3, 5, 7, 7...
Vilma: 3, 5, 5, 7, 7...
Orange hat: 1, 3, 3, 5, 5...
Jochalos: 1, 3, 3, 5, 5...
Micro Tina: 1, 3 (growth in progress, but I predict a 1, 3, 3, 5, 5 pattern) Update 1/4: It does follow a 1, 3, 3, 5, 5 pattern.

It seems that whatever genes involved that produces smaller micros also reduces the maximum number of primary leaflets from 7 to only 5. If that is the case, we can systematically categorize micro dwarf tomato varieties by leaf development alone. It could be as follows:
Micro 5-leaved: Small micro dwarf plant with a 1/3/5 growth pattern. Terminates main stem growth at 8-9 leaves.
Micro 7-leaved: Medium sized micro dwarf plant with a 3/5/7 growth pattern. Terminates main stem growth at 8-9 leaves.

However, we know from the research articles stated that 5 leaves are still expressed in the absence of the determinate(sp) gene, as shown in the image here of Micro-Tom bred with the indeterminate gene(https://media.springernature.com/full/s ... pg?as=webp).
Despite that, the internode length in the stem are considerably taller compared to the regular micro tom. This leads to an interesting idea that dwarf indeterminate tomatoes could grow even smaller than what Craig LeHoullier has had developed so far.

I will provide images on a later date as I continue my observations.

[KaguyaCloud]

I think I have a running theory now of the potential phenotypes of micro dwarf tomatoes. However there doesn't seem to be many visual characterizations of it anywhere that I can see. But I will attempt to hypothesize a classification system based off of personal observation.

What are micro dwarfs? A micro dwarf is a dwarf variety of tomatoes that, in addition to the dwarf gene(d), has another gene or more that is responsible for further shortening the stature of the plant. These genes can include a determinate gene(sp), and/or potentially other undiscovered miniature genes(mnt, mnt2, etc).

Using this diagram, we can attempt to characterize the genes.

The dwarf gene(d) causes rugose leaves and decreases internode leaf length. One may assume that it also decrease the number of primary leaflets from 7 to 5 based on the diagram above, however we know that micro dwarf plants with the d gene(like Vilma), can develop full 7 primary leaflets with secondary leaflets. Therefore, the addition of another gene might trigger the 5 leaf phenotype.

The determinate gene(sp) decreases internode leaf length and terminates leaf growth after a set number of flowers. Micro dwarf tomatoes can exhibit indeterminate(Sp) growth, such as Inkspot, but it is somewhat uncommon. The vast majority of micro dwarf plants that have been bred with the determinate gene.

Hypothetically, it seems that the mnt genes are responsible for suppressing secondary leaf growth, as shown in the diagram above. It seems to also cause leaves to only develop into 5 primary leaflets instead of 7 primary leaflets when combined with the dwarf gene. Further crossing is needed to determine this.

Micro dwarfs can be categorized as followed:

Indeterminate micro dwarfs: These micro dwarfs contain the dwarf gene(d) and potentially mnt. They exhibit 5 primary leaflets when grown and have a predominantly indeterminate growth habit, where a central stem grows upwards, grows a flower truss, and then proceeds to grow another set of leaves and flower trusses. The length between leaflets is also elongated like a typical tomato leaf. One has to be careful in breeding these, as it is statistically possible to develop only a dwarf indeterminate tomato variety with just d and nothing else.

Determinate micro dwarf: These micro dwarfs contain the dwarf gene(d), the determinate gene(sp), and potentially mnt. Mnt is not necessary to produce a determinate micro dwarf, however the inclusion of the gene allows for a smaller compact growth pattern. Determinate micro dwarf tomatoes can be sub-categorized in these potential phenotypes.

Micro determinate 7 leaflets(MD7): This category contains d and sp, but not mnt. It exhibits a compact growth pattern with mature leaves that have 7 primary leaflets as well as secondary leaflets. Based off of data extracted from renaissancefarms.org, they range between 8-12 inches in height.

Micro determinate 5 leaflets(MD5): This category contains d, sp, AND mnt. It exhibits a compact growth pattern with mature leaves that have 5 primary leaflets with little to no secondary leaflets. These range between 3 and 8 inches in height.

There is a theoretical third category as shown in the diagram above. And this is a micro tomato without the dwarf gene, but it has the determinate and mnt gene to compensate for height. It is still larger than a micro dwarf tomato, but may be much smaller than typical determinate varieties. This category would exhibit regular leaves, but with little to no secondary leaflet growth. Using pixel measurements, mature height would be around 15 inches or so assuming the Micro Tom in that image is 4 inches tall. But should this be classified as a micro dwarf tomato? It isn't really a dwarf in the classical sense, but it is still considerably smaller. If so, maybe the naming convention "micro dwarf" might need a revision to just "micro".

Hopefully this classification system may be more helpful in anyone else who wants to breed micro dwarf tomatoes in the future.

It may be more efficient to select towards Micro dwarfs with 5 leaves(potentially d and mnt) that are heterozygous for the sp trait in F2. Then we may be able to select the sp trait in the F3 generation.

[KaguyaCloud]

12/27/23 Update.
It has been 24 days since I planted my micro seeds.

I have reached a point at the maturity of both tomato varieties (Jochalos and Rosella Cherry), where I can cross pollinate the two. I have compiled a general summary of what I did below. And it was difficult. Hopefully I get a fruitful result, I just need one seed to grow into an indeterminate plant to show that the cross has been successful. Also during my last few months of practicing emasculation on my Orange Hat micros, I've noticed that successful pollination occurs when the stem that the flower sits on becomes slightly stiffer to the touch.

https://imgur.com/a/ba7648W

[HL2601]

Great images! I am wondering why you didnt use an electronic toothbrush to collect more pollen? Did you find just passing the point end tool in collected enough?

[KaguyaCloud]

Great images! I am wondering why you didnt use an electronic toothbrush to collect more pollen? Did you find just passing the point end tool in collected enough?

Excellent question! I used the technique described in this video: https://www.youtube.com/watch?v=Q8JRKujawII&
It's relatively low tech to do, which I would prefer. Any thin and/or flat end of a screw driver will do(I think I could even use the ear wax cleaning tool too now that I think about it). I found that I can collect enough pollen that collects into a dot that's large enough to cover the female end of the flower. At that point, I gently patted the pollen onto it. I think that should be sufficient enough for fertilization. But I will find out if it is enough.

[bower]

Update 12/22/23:

All varieties(including regular indeterminate Rosella Cherry) developed flower buds at around 20 days of growth when grown with around 29 DLI and ample nutrients. Jochalos, while having more leaves, is still shorter and smaller in growth stature.

That must be a typo??? 20 days to flower buds??
I've only grown one micro, but it was similar to other tomatoes iirc at around 80 days from seed to flower.

[KaguyaCloud]

That must be a typo??? 20 days to flower buds??
I've only grown one micro, but it was similar to other tomatoes iirc at around 80 days from seed to flower.

Fortunately that isn't a typo. My Jochalos is now 26 days old and is currently blooming as we speak.
Here's a photo album of the tomato plants as of today: https://imgur.com/a/iWxp2X9
My Rosella Cherry tomatoes are 17 inches tall at the moment. I rooted a sucker from the Rosella plant into a smaller pot 2 weeks ago, and it's already growing flower buds.

Around 3 weeks to flower buds is average to me with my indoor conditions. Then another 6 weeks to ripe fruit. I have a very detailed means of growing them, and am doing other things to make growth habit more efficient. I don't only measure light by how many hours a plant receives, but by how much light falls on the plants on average(kind of like rain, it's called DLI). Here's a summary of my set up:

I generally give the very top canopy of my tomatoes about 40,000lux(about 571ppfd) of light at 14-16 hour intervals.
I use relatively moderate cost bar lights($10 per 2ft bar, Monios T8 White Lights).
The growing media is Fox Farm Ocean Forest.
I use a ZeroWater filter to measure nutrient levels leaching from the bottom of the pots(400-800ppm is a good range).
I use a reverse osmosis filter water for my plants.
I solely use MaxiGro 10-5-14 hydroponic powder, diluted to 38g per 5 gallon bucket to fertilize my plants when the leachate drops after watering with filtered water.
My indoor temperature ranges between 74-80F.

I've read quite a lot of books and science articles on growing plants over the last 3 or so years I've been gardening indoors. All the knowledge I've accumulated has reached me to this point so far, and I'm sure I'll learn much more in the future as I try my hand to breed a decent tasting micro tomato. I plan to make my own potting soil as well whenever I begin growing the F2s to keep the conditions very consistent.

Theoretically if absolutely everything was ideal, I could breed up to the F6 generation in just under one year assuming I can get from seed to the breaker stage of the first tomato is every 55 days(And my first grow attempt with orange hat micros was 65 days).

[bower]

I guess the micros have been strongly selected for earliness - 55 days to breaker is earliest I've ever heard of.
This would make it worthwhile to grow indoors.
Getting buds in 6-8 weeks is typical for regular/'early' tomato seedlings given the 'cold treatment' they need to survive here.
The time from open flower to breaker fruit runs 30 days to about 45 days for larger fruits, that is, first fruits so early season records.
You say 3 weeks from seed is about average for flower buds - do you have records comparing different micro varieties?
Just wondering about genetic vs environment effects on the early maturity. Thanks!
(Rooted suckers btw, are expected to be earlier than from seed, due to the pre-existing plant maturity)

[KaguyaCloud]

Recently I've grown around 4 micro varieties and they have all developed flower buds at around the same time. Here are the varieties I grew and the number of days it took to get to flower buds:

Orange hats: 21 days(Planted 12/8/22, first buds 12/29/22)
Jochalos: 17 days(Planted 12/3/23, first buds 12/20/23)
Vilma: 17 days(Planted 12/3/23, first buds 12/20/23)
Micro Tina: Work in progress.

Rosella Cherry(regular indeterminate): 18 days(Planted 11/19/23, first buds 12/8/23. Power outage 1 day).

I think regardless of even genetics of being a micro vs a vining indeterminate, an optimum environment that allows the plant to grow the correct number of leaves before flowering at the same time. You said it yourself that with your own conditions that every variety was consistent. In my conditions, I am quite literally providing the equivalent of giving the plants 2 days worth of full sun.

You can potentially measure how much light you're giving by either buying any $20-30 LX-1010B lux meter or by downloading the "LUX Light Meter FREE" on iOS. 1 ppfd is around 70lux. So divide the number of lux you have by 70 to get ppfd. Then once you have the ppfd, you can use this formula:
DLI = PPFD x light hours per day x (3600/1,000,000)
The goal is around or at least 25DLI.

[bower]

Well, I always knew that temperature made a difference but really nice @KaguyaCloud to have a real data point to compare with our grow setup here! Thanks for posting about it.
FWIW I also happened on a comment from the breeder of "Ultra Early" varieties, A.A.Boe, where he gives degree day or "heat unit" values for earliness instead of "days". And he says it's more accurate. (of course!)
https://library.ndsu.edu/ir/bitstream/h ... sequence=1

Certainly speaks to the value of a temperature controlled environment for breeding work (or production for that matter).

[KaguyaCloud]

Certainly speaks to the value of a temperature controlled environment for breeding work (or production for that matter).

That article was a really interesting read. Thank you for that.

Oh for sure, escaping from extreme temperatures does help with the growing process. That being said, the most common limiting factor for plants, assuming that temperature and watering are optimal, is light and nutrients for the most part. A plant grown under shade vs full sun or grown in cloudy weather vs a desert will differ in maturity time regardless of the number of "days" passing. I'm a little confused on why the earliness of time to maturity is based off of how many days after a seedling tomato is planted instead of the number of days have passed after growing from seed. The seed packet for my Rosella Cherry tomato recommends starting indoors 6-10 weeks before planting outside and says "70 days", but my plant is already flowering and fruiting at the 6 week mark.

It's my personal opinion that time isn't really that good of a metric, especially considering that weather conditions, latitude, or purely being grown indoors are very major factors of how much sunlight plants can absorb to create more biomass. Heat units as the author proposed is good if one does not live in an area where cloudy days dominate entire seasons(the U.K. for example). I find that with the values I have, an even more accurate measure that assumes optimum temperature ranges is Daily Light Integral or the number of moles of light per meter squared hitting the plant every day, multiplied by the number of days it takes for a plant to reach a certain developmental stage. In my case with around 30DLI over the course of 17 days, I can say that the Light Units needed to grow just the flower buds(not full bloom) is around 510 Light Units.

Another way to determine maturity is just to see how many leaves the tomato is growing before creating a cluster of flower buds. Most tomato varieties are genetically homozygous for the most part, and I have mapped approximately the number of leaves it takes for a plant to reach developmental maturity for the varieties I have grown so far. For example, assume the same tomato variety, a seedling with 4 leaves that is 40 days old may be less mature than a seedling with 7 leaves that is 12 days old due to differing environmental conditions.

[bower]

WRT the number of leaves before the first cluster, that trait has been found to be under separate genetic control from other growth habit traits. 7 seems pretty common, but I've seen as many as ten or more, and conditions being equal, it does make for later flowering. In a determinate plant, sometimes the larger number makes for a more productive plant, if other trait(s) and conditions encourage branches to grow from all the axils.

[KaguyaCloud]

In that case, a Jochalos x Rosella Cherry cross might be a very interesting cross. Based off the research data on hybridizing Micro Tom and another determinate M82, crossing two varieties with different number of leaves before the first cluster resulted in the F1 flowering between the two values. With Jochalos creating 9 leaves before flowering and Rosella Cherry creating 8, I wonder if what the results may be.

Rosella Cherry is a very vigorous indeterminate that has a heavy tendency to create many axillary shoots, it might be a beneficial trait to pass down. But, there are only so many genes that can be isolated all at once. I am already pushing it attempting to isolate only 3 non-linked genes.

[Doffer]

@KaguyaCloud For generative growth, it is important for tomatoes to have hot day temperatures and low night temperatures. They call the temperature difference between day and night DIF. The greater the DIF, the more generative growth and the earlier and multiple flowers are produced. The average 24-hour temperature is important for the overall growth of the plant (day and night together).

If you put 40,000 lux on your seedlings with artificial light, I suspect that the temperature during the day is much higher than at night, have you ever measured this?

[KaguyaCloud]

@Doffer I just measured it just for curiosity. I have 78.5F directly under the lights and 77F away from the lights. I am using LEDs and my shelving system is a wired rack, so that might be a factor as to why the temperature isn't that high. I think temperature is pretty consistent in my living space. The largest temperature difference would be in the summer, where it would be 82F during the day and 76F during the night.

[Doffer]

In my grow tent I have an E-heater that keeps the air temperature at 18C. When the LED lights turn on, the temperature for the leaves becomes 26C (I have to leave the thermometer for half an hour because it has to warm up due to the radiation).
Strange that there is no temperature difference in your place?

[KaguyaCloud]

My set up is pretty open, there are no grow tents, coverings, or side reflectors at all. It's possible that most of the heat generated is diffused into the surrounding area. Also my LEDs are not that powerful at all, each bar light uses about 24W of energy(but realistically only draw about 19W). I can get away with using 3 60cm(2ft) long lights to cover a 60x18cm area(22x7in) and get around 40,000lux of output in most of the region.