Micro-Tom. A Miniature Dwarf Tomato

[KaguyaCloud]

After scouring the internet and libraries micro-dwarf varieties, I have compiled essentially a history of the first known "miniature dwarf" called Micro-Tom.

Before 1989, there existed tomato varieties that today we would classify as micro-dwarf. They consisted of tomato varieties that were determinate with the sp gene, had the dwarf gene d, and possessed shortened internodes. Examples include Florida Basket, Tiny Tim, and Red Robin. However, these varieties were different than Micro-Tom, as they had large leaves and did not seem to terminate immediately to 2 flower clusters after growing a set number of leaves on the main stem. You can see that the main stem of variety "Florida Basket"(Parent of Micro-Tom) continues to produce flower clusters and fruit like a normal determinate here: https://www.gardentags.com/profile/abbe ... ket/624309

There were papers in 1989 and 1990 that had more descriptions and direct quotes from the breeders about Micro-Tom's release:
1989 news article on Micro-Tom: https://ufdc.ufl.edu/UF00028309/03398/images/2

"Other dwarf plants are short, but their leaves are still comparatively large relative to the rest of the plant. It's so small genetically that even if you put it in a larger pot, the plant will still stay small", said Jay Scott(one of the breeders responsible for Micro-Tom)

1991 news article on Micro-Tom: https://ufdc.ufl.edu/UF00028309/03463/images/4

"Other dwarf varieties tend to have big leaves and large fruit out of proportion to the size of the plant. Micro-Tom has more of a decorative appearance with its small fruit, small leaves and small canopy", said Jay Scott

It seems that what distinguishes Micro-Tom from other small dwarfed cultivars is, at the very least, reduced leaves and fruit. I still find it strange that immediate termination to two flower clusters isn't described in the early literature. However, modern day research does show that this does in fact exist in Micro-Tom as shown in this research article on page 13: http://www.lcb.esalq.usp.br/publication ... p11-19.pdf. From personal experience of growing several reduced leafed micro varieties(Jochalos, Orange Hat) and a direct progeny of Micro-Tom(Micro-Tina), this main shoot pattern remains consistent.

With the help of users Sledgehammer Potato, @maf, and William Schlegel from another plant breeding forum, they directed me towards certain genes and to search through the pedigree. Unfortunately the original article written by the breeders for Micro-Tom from 1989 did not exist in any known place accessible by the internet, until now. I have gotten my hands of a scanned copy of the article and it's freely available online here: https://files.catbox.moe/7p01cd.pdf

The pedigree of Micro-Tom, tested as Fla. 7191, is given in Figure 1. Seed was increased in the F 12 generation after a cross between `Florida Basket' (Fla. Agr. Expt. Sta. Circ. S-283) and Ohio 4013-3. The former provided the dwarf plant habit and Fusarium wilt race 1 resistance (Florida Basket segregates for this resistance). Ohio 4013-3 was the source of diminutive leaf and fruit characteristics.

Based off of the article, it seems that reduced leaflet count and potentially early main stem termination came from Ohio 4013-3, as we could assume that Florida Basket does not have those particular traits other than short internodes and the dwarf gene. Fortunately Ohio 4013-3 has descriptors of it's ancestors in parenthesis being an F4 cross between Moneymaker x Geminix x Adagio x Stupicke x Sonato x L. minutum. If anyone has any information about the other cultivar names in that list, that would be helpful. At the very least, those were described to be part of a "European cold tolerance breeding work."

L. minutum was an interesting addition to Micro-Tom's past. Lycopersicon minutum was not an official species name, as the it was split into two distinct species: https://vcru.wisc.edu/spoonerlab/pdf/To ... ograph.pdf

Using data from morphological characters, mating systems, ecological preferences, reproductive isolation and allozyme types, Rick, Kesicki, Fobes, and Holle (1976) described two new species, L. parviflorum and L. chmielewskii, from the central Peruvian Andes. These two species were previously referred to as "L. minutum," a name never validly published (Chmielewski & Rick 1962). Lycopersicon parviflorum was shown to be strictly autogamous, with small flowers and style included in the anther tube or slightly exserted, whereas L. chmielewskii is autogamous and facultatively allogamous, with larger flowers and exserted styles and stigmas. Lycopersicon chmielewskii was considered as the ancestral species from which L. parviflorum evolved (Rick et al. 1976). Fertile hybrids among these two sibling species were obtained experimentally by reciprocal crosses, but no natural hybrids were found in sympatric populations (Rick et al. 1976).

On page 4 and onwards of this article, we have images of both species. Lycopersicon parviflorum seems to be the one of most interest: https://link.springer.com/article/10.1007/BF00281917

Leaves broad, flat, interrupted-pinnate, 6-9 cm wide x 7-10 cm long, with 2, occasionally 3, pairs of opposite major segments and variable numbers of small foliolules, margins serrate or undulate, pseudostipules lacking, the leaves in their simplest form resembling those of L. peruvanum var. humifusum.

Short internodes, very small flowers, and 2 pairs of opposite major segments and leaves showing 5 major leaflet patterns. This could be one of the reasons why Micro-Tom's leaves were reduced genetically, as it is an ancestor to this particular wild tomato species. And, to add to more confusion and clarification, Lycopersicon parviflorum was again renamed to Solanum Neorickii. So this one possible ancestor to Micro-Tom is a variety that went under at least 2 name changes and reclassifications(L. minutum => L parviflorum => S. neorickii). Thanks taxonomists.

Overall, I do not think this should change the definition of what a micro-dwarf may be. However, I hope this clarifies on micro-dwarfs that have traits similar to Micro-Tom. My objective is to breed a new micro dwarf variety. After all this research, I think I will select for reduced leaves and early termination of the main stem to start with.

[AKgardener]

Thank you for all the reading material.. I’ve noticed micro Tom and micro baby along with Tina are all pretty much the same height and size for the most part.. I’ve got a few Tom’s going I always start those before I start all my main crop tomatoes because there fast growing and give me the boost I need to start the season.

[maf]

Fortunately Ohio 4013-3 has descriptors of it's ancestors in parenthesis being an F4 cross between Moneymaker x Geminix x Adagio x Stupicke x Sonato x L. minutum. If anyone has any information about the other cultivar names in that list, that would be helpful. At the very least, those were described to be part of a "European cold tolerance breeding work."

I don't know anything about Geminix or Adagio. Sonato only that it seems to have been a commercial variety in the 1970's and 80's.

Moneymaker AKA Stoner's Exhibition - Old English variety introduced around 1913. Known for being a reliable producer of good looking (for round red) but not good tasting, medium fruits. Ordinary indeterminate habit, large plants, don't know what this would have brought to the Ohio 4013-1 table.

Stupicke AKA Stupice - Czech variety (actually at least 2 varieties, one for greenhouse production and one for outdoors) from the 1950's particularly known for earliness. Interestingly a compact indeterminate, but not dwarf (d), plants usually get to 4 feet or less. So, potentially could be a contributor to earliness and compactness in Micro-Tom. Tatiana lists the parents as "Mikado x Sláva Porýni x Solanum racemigerum." S. racemigerum is a synonym for S. pimpinellifolium.

Thanks for uploading the Micro-Tom article. Unfortunately I can't seem to access page 3 and page 5, just coming up blank. Don't know if it is a problem my end or an upload problem or if the article you received in the first place was missing those pages?

[KaguyaCloud]

Thanks for providing info on those specific varieties.
It's possible that they might've started off trying to domesticate one of the species classified under L. minutum, as the fruit of both are green when ripe and extremely small. Crossing a high performing, red fruited variety such as Moneymaker doesn't seem unreasonable to do in order to increase yield. Maybe I'll try to find any information about Ohio 4013 to see if I can dig anything up.

Thanks for uploading the Micro-Tom article. Unfortunately I can't seem to access page 3 and page 5, just coming up blank. Don't know if it is a problem my end or an upload problem or if the article you received in the first place was missing those pages?

Strange, all the pages should have visible text on them. Let me re-upload another here: https://files.catbox.moe/7p01cd.pdf
Let me know if you have any issues, and I'll try to find a different uploading source.

[maf]

Strange, all the pages should have visible text on them. Let me re-upload another here: https://files.catbox.moe/7p01cd.pdf
Let me know if you have any issues, and I'll try to find a different uploading source.

Hey thanks, I downloaded it this time and I get all pages. Still 2 pages missing when I view it within the browser (Firefox). Very strange, never usually have issues viewing pdf files in a browser.