bower wrote: ↑Thu Jul 11, 2024 7:16 am 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.

Understood. If that is the case, then it should be easier to select for the micro traits, as they do not have any flowering patterns(with exception to their axillary shoots) and immediately terminate with the determinate gene and early flower termination genes.

Update 7/16/24

Very strange things have happened. The two smallest Joro F2 seedlings that I have kept seem to have a very…perplexing growth pattern. They terminate at 2-3 leaves with no flower trusses and no further main-stem growth. Side shoots have proceeded to grow in their stead. I do not think this is a coincidence or freak mutation, as 2 of the 18 sprouted seedlings exhibit this behavior despite the differences in leaf shape.

I do not know if these side shoots will yield any fruits or if they will terminate with flower clusters, but there’s potential for possible sterility if the pattern continues. The micro dwarfs I have grown do exhibit a more complex leaf and flower pattern on axillary shoots.

I wonder if there is an earliness gene from Rosella Cherry has influenced the growth habit significantly, as this may explain why the F1 flowered and fruited much earlier than both parental counterparts. Either way, I will continue my observations.

Tomato and pepper 'mules' do turn up from time to time in people's seedlings. It's common enough that most growers will end up seeing one after some years of starting many seedlings, but much more uncommon than 2 in 18.
I've never read any technical explanation of it, and they do occur in conditions where many other seedlings developed normally, so it doesn't seem that environmental conditions are involved.
I seem to recall having two from the same batch of seeds one year - I kept one of them on the bench and eventually it did develop a leader, but I don't recall potting it up or getting fruit. I think it was just too late.
OTOH it may be that there's another explanation, other than chance, for these two 'unflowered' seedlings, and you may indeed develop leaders that bloom - if so, it would be interesting to see if the strange pattern is heritable.

A mule huh. The genetic differences between these two varieties are quite extreme to begin with. This will certainly be interesting to explore out. I’m debating between selecting for more dwarfs or focusing on the two I have at hand that are already quite compact.

I’m hopeful to at least obtain some tasty fruits from these two seedlings if they do grow a budding leader from an axillary shoot. Early branching doesn’t seem to be inherently disadvantageous. Extremely compact size is actually quite beneficial, as it makes it even more friendly to my indoor conditions.

This phenotype for some reason is strongly affected with the dwarf(d) gene if we were to assume that dwarf seedlings do not close their cotyledons during the night cycle. Perhaps if I continue selecting more dwarf seedlings, I should eventually see a more conclusive ratio of this phenotype.

It is quite weird to me, because there should be a 3/4 chance that these dwarf expressing seedlings should be a dwarf indeterminate, but 100% of them seem to terminate extremely early. This could be due to very low sample size, however.

That is interesting about the early termination. I don't know enough about typical dwarf growth habit to suggest an explanation. But strange things can emerge in crosses due to some unexpected combination of the less visible traits in the parents.

One thing to love about tomato breeding is that the seeds are so long lived. If you want to spend a while growing only two instead of selecting more with a second batch right away, there's nothing to stop you from going that route later. Of course with your setup, the wait is not even that long!

Update 7/21/24


Good news, the axillary shoots of the 2 smallest seedlings I have selected seem to be growing in a vegetative phase. This is quite perplexing, as usually the axillary shoots of the micro dwarf parent Jochalos usually grows flower trusses after the third leaf followed by a determinate flower and leaf pattern. The statures of both are still quite small, which may indicate that some recessive dwarfing genes were well preserved this generation. I'm worried that the early flower termination gene has not been preserved for either of these two.

Left F2 plant characteristics: Very smooth leaf edges like Jochalos. Rugose leaves expressed on the axillary shoots. Leaf reduction gene expressed, as it is following the 1, 3, 3, 5 pattern. Extremely short internodes at around 0.5cm. The two axillary shoots sprouted on the first and second true leaf of the plant.

Right F2 plant characteristics: Toothy leaves from Rosella Cherry. Rugose leaves expressed on the axillary shoots. Leaf reduction gene seems to be heterozygous like the F1 parent, following a strange 1,1,5,5 leaf pattern. Internodes around 1cm. The two axillary shoots sprouted from the cotyledons of the plant instead of the true leaves. I wonder if the longer internodes may hint that this one may be an indeterminate, as micro-tom introgressed with the indeterminate gene did express much longer internodes and longer spacing between pairs of leaflets.

Great pictures, the shape of these plants is really novel!

Update 7/22/24


I planted the Joro F2 7/4/24. Subtracting 2 days from the power outage, that makes it 16 days from open cotyledons to flower buds. It seems that the rightmost F2 may not have the early termination gene due to a leaf following right after the flower buds. But it is too soon to know for certain just yet.

Update 7/26/24
Exciting developments!


It turns out that both F2 plants express very early flowering patterns, with all stems flowering after 7 true leaves(which is much earlier than both parents with 8 and 9 leaves to flowering). A very surprise twist of genetics is that the F2 with the longer internodes actually has the early stem termination gene, meaning that early termination could be independent of short internodes and compact leaves. We do know that early termination is independent of genes involving regular long leaves, but still quite the interesting development.

Left F2: 7 leaves to first flower truss. Compact leaves and shortened internodes, similar growth habit to micro dwarf Jochalos. Leaflet reduction gene expressed. However, no early termination gene was conserved due to the fact that more leaves are forming after the first initial flower truss. It is either has a standard determinate or indeterminate flowering habit. The compact habit combined with a standard determinate flower and leaf pattern would still put it similar to Micro-Tom's parent Florida Basket. I would not really consider this to be a true Micro-Tom-like micro dwarf since there isn't early stem termination. Either way, if the fruits taste good, I think starting a line of extremely compact indeterminates or Florida Basket-like micros is an exciting venture that I'm sure others would be interested in.

Right F2: 7 leaves to first flower truss and early stem termination. Open growth habit with long internodes and longer spacing between leaflets compared to the typical micro dwarfs I have grown. Leaflet reduction gene expressed as no leaves after the 6th has 7 leaflets. Early termination gene expressed with both stems immediately ending at 2 flower trusses. Flower trusses have extreme branching and has the tendency to grow a leaf on the flower truss like the F1 generation. By my definition, this would be the micro-dwarf phenotype that I'm looking for.

This was quite a lot faster than expected, as I thought I needed to grow tens to hundreds of seedlings for the early stem termination gene to come up. I assumed it needed 3-4 combined recessive genes to be expressed(dwarf, determinate, early termination, shortened internodes). I probably got extremely lucky. Now it seems that extremely short internodes is not required for early stem termination to be expressed. Maybe this F2 isn't as similar in terms of super compact growth habit like other smaller micro dwarf varieties, but that only means more potential flavor genes preserved from the tasty indeterminate cherry parent. Despite the longer internodes, I am expecting that the growth habit will be relatively compact than the F1. Dwarf, early stem termination, and flavor are the only priorities at the moment. I'm looking forward to the F3 generation in the next month and a half or so.

Update 7/31/24


First flower appeared in the left Joro F2. And the number of petals is 8, which is quite a lot more than the standard 5-6 from the previous generation. The truss branching is very considerable for both F2s, as I have counted up to 15 flower buds per single truss on both plants. I'm quite unsure if the plant is able to support that many fruits at a single time, but I'm excited to see it it's possible. Micro dwarfs already have an extremely high amount of fruits per volume of space taken up, and the branching trusses likely will push that density even further. It makes me wonder if having a more open growth habit will be advantageous with the amount of fruit set that I am expecting.

Left F2: The more compact F2 seems to have grown 4 leaves followed by another flower truss in the main stem after the first flower truss, but the growth of that has been considerably repressed. The main stem growing tip seems to be growing much slower than the axillary shoots of that same stem, despite the axillary shoots being shaded by the leaves above.

Right F2: Growth habit is very open. Internodes ranging from 0.5-1inch long. It's practically behaving almost exactly like the F2, except for the fact that it terminates immediately. However, the left stem seems to have grown 1-2 leaves in the flower truss. The leaflet structure are very reminiscent of the F2 with long and spindly leaves, but with the even more subdivided leaflets coming from the primary leaflets like Rosella Cherry. Axillary shoots coming from the stems start off with 3 or 5 leaflets(instead of the 1 like in normal micros), but grow only 2 leaves before another flower truss appears like the micro dwarf parent. It's possible that the early termination trait is linked to the trait involving skipped leaves to first flower in the axillary shoots. I wonder if the twin stems that grew initially are actually true micro main stems instead of the typical axillary shoots, which is quite an interesting observation. Some genetics is seemingly causing the main shoot to terminate and the axillary shoots to grow immediately into a reduced sympodial pattern.

Wow they've grown a lot!
WRT the early termination and large number of buds on one stem, I'm growing a Tom Wagner determinate variety called Favorie de Bretagne which might be similar (although not a microdwarf). Fruit set is very high but still there are large numbers of flowers that don't set and drop instead. That might be conditions in the greenhouse, or it may just be the plant strategy that it doesn't need the excess of blooms and just drops a lot. I notice that Mini Rose from Ottawa station also has large and many clusters but dropping the majority. Anyway, the key thing with Favorie de Bretagne growth habit is very sprawling and these branches all with 3 or more large clusters of flowers are able to deal with the fruit weight by sprawling it seems. The plant can also afford to drop lots of blossoms and still have a high yield.

I found a link to images of the Favorie de Bretagne variety: http://delagrainealaplante.fr/mes-fiche ... .php?id=89

Huh that’s quite a strange tomato. Does it terminate to 2 flower buds without any sympodial patterns and then grow axillary shoots with sympodial patterns? Maybe sprawling/basket tomato varieties have this trait, I haven’t grown any myself to compare however.

It doesn’t seem to have the dwarf gene based on how smooth leaves are. It also doesn’t seem to have the leaf reduction gene based on how massive the leaves are. However, it does seem to have very smooth leaf edges and a compact flower truss that reminds me of an introgressed variant of Micro Tom.

When the dwarf gene for Micro-Tom is bred out, the morphology looks somewhat similar to Favorie de Bretagne, but with a smaller fruit set.
https://www.esalq.usp.br/tomato/Dwarf.pdf

The micro tom with the wild type dwarf gene seems to still terminate early, but the axillary shoots seem to still follow a high density fruit set. I wonder if the genetics are related.

I’ve heard that many multi-flora varieties do the same, putting out hundreds of flowers but only setting fruit on a fraction of them(eg Barry’s Crazy Cherry). The fruit set is still very high density. I’m sure the tomato does have self regulating mechanisms, as the amount of fruits that could potentially accumulate may not be sustainable.

From my personal accounts growing Rosella Cherry, it seems that it also drops flower buds during periods of low nutrition and low amounts of light.

In my breeding here I've personally selected for plants that have few blossom drops, because in the context of cold and wet weather a large number of drops tends to seed mold. have not seen that this season, but we haven't had the weather either, especially since I started late.
Favorie de B. has very short internodes and a large number of axial shoots, all of which have three clusters of flowers before terminating. At least that's what I recall - just went down to check and it's too dark to confirm. It could be the brachytic gene, making the short internodes. Reminds me of the super compact sprawling habit in @Pippin 's lines. Very interesting and I am curious about the genetics - I have made a couple crosses that took, so it will be fun to see how that plays out.
I agree 100% that the plants have mechanisms for deciding how much fruit is sustainable, and either drop or wait whatever they can't handle. Strategy of producing a surplus of flowers is interesting, and if it doesn't cause disease, why not.

Update 8/3/24


Many flowers are blooming. One slight quirk of this branching truss trait is that the fruits will be developing in stages instead of all at once. I remember that Rosella Cherry didn't put out and ripen all of the fruits in the vines all at once, but grew and ripened in layers of fruits at a time before further growing more branches.

Left Joro F2: The flower truss is branched and compact, but with very strange looking flowers. Not only do some have 8 petals, but the stamens are twice as large as the F1. It's almost as if two were fused together. The sepals are short like the micro dwarf parent, but curl like the indeterminate parent. Axillary shoots do not show signs of following any micro dwarf axillary flowering habits. This may pose an issue due to the fact that this very compact plant with high instances of regular axillary shoot growth will likely cause extreme amounts of crowding of the leaves and flower trusses in addition to a larger growth habit as time goes on.

Right Joro F2: Large, non-compact branching flower truss. Flowers look relatively normal to Rosella Cherry, but with around 6-7 petals and sepals instead of the standard 5. Sepals are fused like Rosella, but do not curl. Axillary shoots confirmed to grow around 2 leaves before putting out a flower truss, meaning that it will likely stay relatively around the same height as it is right now.

Update 8/11/24


It has been approximately been 11-12 days since the F2 have bloomed and they have already begun to set and develop fruits. I have been pollinating the flowers by tapping and shaking the whole plant to encourage more fruit set.

Left Joro F2: Main stem growing shows no signs of determinate flowering habit. Growth habit is extremely bushy due to compact size combined with normal axillary shoot growth. Axillary shoots seem to behave similarly to the main stem, like Rosella Cherry. Fruits have a flat shape like micro Jochalos. The fruits have expressed the green tops of the parent Rosella.

Right Joro F2: Open growth habit allows easy visibility of the branching structure. Early termination of the main stem and early flowering of the axillary shoots have limited the size. Extremely large number of flowers from the branching truss and early termination of the stem, I have counted over 40 flowers just on the ends of the 2 main stems. Fruits have the uniform ripening gene from Jochalos, but are shaped exactly like the fruits of Rosella Cherry.

It seems that there only several genes required to obtain a micro-like growth habit. The dwarf gene is required for compact growth habit. An early termination gene limits the maximum height and creates a sprawling growth habit. Leaf reduction gene creates reduced and compact leaves with very smooth edges, this might be linked to the shortened internode gene.

The indeterminate gene doesn't majorly affect overall growth habit if it's paired with the dwarf, leaf reduction, and short internodes. But it will cause the plant to continuously grow in height and width. This may be why micro breeders are having trouble after growing past the F2. If the indeterminate gene is preserved, but the leaf reduction or short internodes are heterozygous, then F3+ might express taller growing habits.

The early termination gene is absolutely vital in controlling the growth habit in the smallest micro dwarf varieties. It seems that the dwarf gene with early termination leads to shorter growth habits. It's possible that the determinate gene might be required for this to be expressed.

Joined up here just to tell you how thrilled I have been to find such detailed notes from someone who is so new to the breeding scene. I have significantly more ridiculous goals than you, but my fuzzy ideas for where to begin are very similar to yours. My understanding of breeding genetics was at a grade school level two weeks ago, and it's still minimal - but your commitment to talking through your observations and working theories has been invaluable. Thanks to both you and the responders who have discussed what you're seeing in plain english, as well as posting excellent pertinent articles and studies for further reading. I can't tell if you're lucky, good, or both - but I'm thrilled to see your early success.

I am also mostly shackled to indoor space, but I do have the ability to convert more space. I'm also trying to find some community garden space to grow some 'wild' types, but that may have to wait until spring. In the meantime, I plan on growing out a large number of micros (and, likely, some of the more recent dwarf releases selected for better flavor) to try to choose my parents. I have not decided on my cultivation methods - I'm partial to hydroponics - and might even attempt to test a few versions. I'm not sure if I'll be able to stunt my wilds as well as you (one in particular I know to be a sidewalk crack kind of beast) but I may have to try!

In any event, congrats on already finding some interesting candidates - your project is inspiring all around!

Welcome to the Junction! And no problem, I'm actually quite surprised in the lack of public details for micro breeding when I started. In depth knowledge of genetics isn't entirely necessary for breeding plants, but I would probably stress the importance of very close observation of inheritance and focus on selecting those very few traits. I can't say I fully have retained all the dwarf genes in my F2, but it's fun to see the traits segregating. I'm likely really lucky to even strike a good balance of expressed traits.

Choose your breeding parents wisely. The more differences in traits, the better! I would probably recommend growing a sweet micro parent with the early termination gene, where it grows 7-9 leaves then two flower trusses at the end with no additional leaf or flower trusses after that. I'm expecting flavor genes to be quite a difficult hurdle to overcome. All the micros that I have grown so far either tasted terrible, bland, super sour, or kind of sweet. Sometimes on the same plant. None of which come close to the flavor of a good indeterminate cherry. If you find a parent to cross with the micro, it needs to taste pretty good. My F1, while really sweet, had a very standard tomato flavor and took 2-3 weeks to fully ripen after it turned to its final color. So the genetics from micros seem to dampen flavor as well. I've heard from Bill Yoder in a recent interview with Craig Lehoullier that he hasn't had much luck on preserving flavor for micro dwarfs(Source here: https://www.youtube.com/live/b4ezG6j943 ... T4i&t=3708).

Hydroponics, to me, has quite a lot of pros and cons. Flavor can vary quite a lot when growing using straight hydro from my personal experience. I find it simpler to just grow using a coco coir/perlite substrate and water it with diluted hydroponic nutrients and/or tap water depending on the nutrient levels of the water that escapes out of the container. Nutrient levels are very important, because flavor selection is highly dependent on both genetics and consistent nutrients.

I think my first step is going to be acquire and grow out every compact dwarf variety I can get my hands on, and play around with stunting larger cultivars. I'll probably mirror your cultivation methods (which I see as something of a crossbreed that might already yield most of the benefits of hydro cultivation) but I'll also probably rig up a few simple systems to compare results. I've read about good results flavor wise by moving plants to 'soil' for fruiting, so that'll be something to explore as well.

Anyway, this is your community and thread, I'll have to find my own home for my notes. I'll be following along with great interest! Your observations regarding the 'corkscrew root' behavior were particularly interesting to me, and I would have been blind to it with my typical germination methods. If only all 'amateurs' were as detail oriented as you!

Curious of what kind of grow lights you use?? I’ve been up and down with mine