Author Topic: Planning for a 2023 tomato breeding project  (Read 327 times)

Cathy A

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Planning for a 2023 tomato breeding project
« on: 2022-06-17, 09:05:50 AM »

I'm beginning to make plans now for a small-scale tomato breeding project aimed at getting varieties well adapted to zone 4 Vermont. Goals include a long, productive season; ability to reseed, sprout, and make productive fruit without needing to be pre-started inside; some frost tolerance, able to handle ~30F without cover or mid-20s F with cover; and ability to set fruit when nights are below 50F and days are cool but not cold; and tolerance for growing and fruiting in less than full sun.

I've been gardening in this location for almost 10 years, including tomatoes for most of that time. I've tried a number of varieties, including Sub Arctic, Siberian, Celebrity, Sungold F1, Amish Paste, Roma, Brandywine, Black Cherry, Isis Candy, and a few others.  Generally any of these produce good tomatoes in my location, growing in excellent soil (not my native clay, class 6w) in well-drained raised beds. They get good sun for some hours a day, but there is no place in my yard surrounded by forest that truly gets full sun. Last frost is historically around May 23, first frost around September 23, though it's not unusual for last frost to be a week or two either way and first frost often has several weeks of Indian summer afterward with little frost. Winter here lasts about 5 months, typically has 1 - 2 feet of snow on the ground from late December through March, and temperatures are routinely below zero F at night during the coldest months.

I have a healthy pollinator population of wild solitary bees, made up of bumblebees or a similar relative. The garden is mostly organic, with no pesiticides used, no major pest issues except snails and slugs (beer traps and hand-picking deal with them), and an occasional use of 10-10-10 to supplement compost.

I can put about three 4x4 beds, 48 square feet, into tomatoes after allowing space for the rest of my garden.  I grow intensively, so each bed could support anywhere from 9 plants with plenty of space each to as many as 25, more tightly packed.

One year early in my Vermont gardening life, I tossed all the unused, unripe, split, going bad, etc. tomato fruits back in the bed at the end of the season expecting them to compost. Many of them sprouted and produced tomatoes the next year, though later than ideal. So I know it is possible to start tomato seeds directly in outdoor soil at this location.

This year I am growing Amish Paste (started from seed myself), Sungold F1 and Brandywine (both purchased as plants locally).  These are not part of the project, which I have only started thinking about in the past week. In previous years I have struggled to start tomatoes from seed indoors, but after upgrading my weak fluorescent lights to proper grow lights, this year it worked extremely well. I use tomatoes both fresh and for tomato sauce, and planning salsa for the first time this year, so a mix of paste and "eating" tomatoes is best.

Right now I'm trying to figure out the best varieties to use for a breeding project beginning in 2023 so that I can order them this fall. A few obvious candidates are:

 Glacier
 Sub Arctic
 Jagodka
 Siberian
 Kimberely
 Black Cherry
 Matt's Wild Cherry
 Roma
 Sungold F1

for a good range of genetic material.   I don't believe any of these have true frost tolerance, so I think it would be a good idea to include Solanum hirsutum, S. habrochaites, and/or S. huaylasense. I don't want too much beefsteak genes in the mix because those tend to be late, which would defeat the purpose.

I'm unsure to what extend this should be treated as a "promiscuous landrace" (thank you, Joseph Lofthouse, for that great term) and to what extent I should push it in the desired direction with controlled hand crosses. If I do succeed in getting a good landrace going, I may eventually try to isolate some homozygous lines with particularly good traits from it.

I see a number of posters on these forums are doing similar projects in different locations, though most of them seem to be in zones warmer than zone 4. So far my online research has not turned up any cultivated tomato varieties that claim true frost tolerance, even those from places like Russia where it might be expected. I did see some mentions on these forums, complete with photos, of a few plants that did survive a frost while most died. How much of this is from Mendelian genes vs. epigenetic switches vs. microclimate doesn't seem to be well understood.

Suggestions are very welcome!

Vesa Tee

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Re: Planning for a 2023 tomato breeding project
« Reply #1 on: 2022-06-17, 01:36:31 PM »
You have an interesting project, I am sure you will get a lot of good suggestions and inspiration from this forum.

You already referred to the Russian varieties, so maybe you have already studied them. One good source of information is Tatiana’s tomatobase, by simply searching there with key words like ”cold tolerant” or ”frost” or ”Saraev” might give you some interesting reading. I have never truly tested these Russian varieties on how cold tolerant they are so I cannot comment them much more than this.

http://tatianastomatobase.com/w/index.php?title=Special%3ASearch&profile=default&search=Saraev&fulltext=Search

William S.

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Re: Planning for a 2023 tomato breeding project
« Reply #2 on: 2022-06-17, 03:32:07 PM »
I grew some of the Saraev tomatoes my first serious tomato breeding year in 2017. My conclusion was that their special abilities were the result of epigenetic activation that had subsequently been deactivated again. That they are in fact pretty ordinary tomatoes which just happened to get some kind of epigenetic effect. Though that suggests that it might be possible to reactivate them. I suspect that when tomato plants survive being exposed to frost that such an activation is one possible outcome. However, I haven't actually observed it yet and now I am in year 6 of tomato breeding!

In 2017 when I started, I had many of the same questions particularly about the wild species. I have to report that particularly in regard to frost and cold tolerance I still don't know for sure. I suspect that many of my favorite short season tomato varieties are cold tolerant and or stress tolerant.

I have relied heavily on the prior work Joseph Lofthouse did including following many of his variety suggestions and working with his varieties and populations. For instance, I have F1 and F2 tomatoes I am growing this year whose pedigree is roughly this: (Unknown Joseph Lofthouse 2017 tomato landrace potato leaf x Blue Gold in the F4) x Big Hill / HX-9 and the pedigree of Big Hill is Jagodka x Hillbilly. So they are tomatoes I have bred from 75% tomatoes obtained from Joseph and 25% from Brad Gates.  I now think of this iteration of the project as the Mission Mountain Morning or MMM for short tomato line. However I already have seeds of the MMM line crossed to Aztek microdwarf and hope to harvest seeds of it crossed to Sweet Cherriette and two currant tomatoes sometime soon!

One important point that arises from that is that you don't have to start from scratch! We all stand on the shoulders of folks like Joseph Lofthouse and Brad Gates amongst many others going back in time a very long time.

I have shared a couple of my tomato projects through Experimental Farm Network and Snake River Seed Company as well as my wife's online Etsy store. I intend to continue with that. I also happily trade seeds with folks here in the USA.

Joseph's promiscuous tomato project which looks to be currently available in the "Wildling" form https://store.experimentalfarmnetwork.org/collections/tomatoes/products/wildling-panamorous-tomato on EFN even right now already contains a substantial amount of genetics from a promising mixture of Solanum habrochaites and Solanum pennellii crosses. In more recent generations the results have been downright edible maybe even palatable or on rare occasions amazing! Likely fresh seed lots will be available for the winter 2022-2023 seed acquisition project. I myself have a fruity flavored isolation garden with two promising promiscuous project strains from my 2021 garden which I have been calling Little Pumpkins and The One. If they taste good again this year I'll have seed to share one way or another.

I don't currently have a whole isolation garden devoted to a cold or frost tolerance breeding project but am interested in that as well, I am unsure how best to proceed with that particular project.

My top ten favorite tomatoes for breeding with after the 2017 tomato season included some things like Sungold F1, Sweet Cherriette, Earl's strain of Jagodka, Krainiy Sever, Blue Ambrosia, and Coyote. 

Now that it is 2022, I am not sure how many of my original favorites are still important. I find new favorites, often from segregating populations, most years.
Western Montana garden, glacial lake Missoula sediment lacustrian parent material and shallow 7" silty clay loam mollisoil topsoil sometimes with added sand in places. Zone 6A with 100 to 130 frost free days

Steph S

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Re: Planning for a 2023 tomato breeding project
« Reply #3 on: 2022-06-17, 04:57:08 PM »
Some excellent points already from Vesa and William.  Standing on the shoulders is what it's all about.  No shoulders, no world of plant breeding. 
I agree with Vesa that the shoulders of the Russian breeders are very worthy of standing upon, when we look for material for cold climates.  Tomatoes are extremely popular throughout Eastern Europe and some very fine OP varieties have come from their stables. I am quite reliant on them myself, for the cold tolerant partner in a cross, as in my trials of over 100 OP's it soon became clear that the Eastern Europeans were far better suited than many of the glorious beefsteaks famous for their flavor in the SE and NE US where the season is quite long compared to ours.
I have accepted the limits of cold tolerance in tomatoes.  Someone else may succeed in pushing that boundary, but it is beyond my capabilities to take it further than has already been done by professional breeders.  I accept that they are frost intolerant, and cultivate and breed those that are tolerant of cold and low light, yet adaptable to extreme temperature changes which we get in the greenhouse when the sun suddenly comes out, while also doing my part to adopt techniques that keep them fruiting, including shelter, temperature moderation etc.  I have seen my most adaptable cold tolerant tomatoes sprout from the stump after frost killed the tops in the fall..  However this is not a meaningful feature for me.  Frost damages the fruit if you fail to harvest before it.   Sprouts from frost killed plants have little chance of producing fruit before it frosts again.  So my focus is strictly on the crop, and not erudite values of "tolerance" which don't produce something to eat.
I have trialed enough OP's to know that many of them will not grow fruit when it's cold, some won't set, and others set but won't grow them until nights hit 60F.  Then there are still a very large group of OP varieties that will set and grow fruit in quite cool conditions.   Setting with nights under 50F is not a problem, but growing fruit when daytime highs don't reach 60 F is pretty much a null group.   
I have had plenty of success crossing between the more cold sensitive tomatoes and those that do better.  Offspring seem to pick up the cold tolerance very well, so I do get food even in early generations of many of these crosses.   There is a huge pool of varieties from Eastern Europe to play with.
In the ones that you mentioned, I have used Black Cherry as a flavor parent in crosses with earlier and more hardy tomatoes.  This worked quite well, the flavor genetics seems pretty dominant and the weaker plants in cold tolerance terms get weeded out without catastrophes like a year of losing half your crop.  There's lots of vigor in Black Cherry but they are sensitive to temperature extremes and prone to produce vegetative growth at the expense of fruiting.  Many yards of vine for a few tomatoes, sometimes.
I've also done some breeding with Kimberley but most of these lines are on hold (pending time and space) because they are chronically susceptible to pests cw other lines.  Kimberley has early flowering genetics which will only produce an earlier crop if the temperatures are right.  So starting them early is a bit wasted.  The trait would be really useful if the plan is to start them later and have them transplanted at 6 weeks of age no later, into temperatures that suit their fruit production.  Kimberley and its crosses can win the bragging rights for first ripe fruit easily enough, for the one that is setting when you transplant them.  The main crop though will not set any earlier than Stupice and similar early varieties, unless conditions are warm enough.  So it was not a key to earlier crops for me.
I don't have a handy list of the varieties trialed and how they worked out but if there's something you want to trial and you run it by us I will remember it if it's one that I grew.  A lot did not get invited back for a second season.   However there are a group of OP's that were good enough for my farming friends to adopt and continue to grow here, meaning that they produced reliable crops in spite of our fickle seasons and became favorites, or at least were worth the occasional grow. 
Cherries are always a great bet if you're growing outdoors.  Any smaller fruit has a much better chance to ripen.
I really liked Isis Candy but they hated my crowded shady greenhouse and only produced when I ditched them outdoors. ;)





Adrian

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Re: Planning for a 2023 tomato breeding project
« Reply #4 on: 2022-06-18, 06:08:02 AM »
We don't have the sames climates and maybe not the sames varietys but we have harvested our first tomato the 1st september the last year It was the varietys san marzano lungo, andine cornue and canestrino di lucca and costoluto tasty but too  late.My idea was to found more early tomato. bloody butcher is the most early for me!
Most early than morettino.
San marzano lungo was the most productive the last year.
Someone has offer  F2 of tiny tim x green velvet. I think i can have early and tasty tomato.
I think more and more to try cross with bloody butcher.The first bloody butcher is mature today this year!
Do  you think its a good idea to cross bloody butcher with dwarf tomato  (tiny tim x green velvet f2)for increase earliness.

Have early tomato is even usefull for us in france.
I think for harvested tomatos the most long time it important to have differents earliness.
A small test for have more early tomato was to did the cross san marzano lungo x costoluto but the F1 is weak.
Maybe if i select F2 i can have a correct result.
« Last Edit: 2022-06-18, 06:45:27 AM by Adrian »

Cathy A

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Re: Planning for a 2023 tomato breeding project
« Reply #5 on: 2022-06-18, 08:36:08 AM »
It's great to hear from so many experienced tomato breeders. This is the kind of feedback that I need. And thank you especially for the reminder that building on existing work could speed things along.

Vesa Tee: "You already referred to the Russian varieties, so maybe you have already studied them. One good source of information is Tatiana’s tomatobase..."

I like Tatiana's Tomatobase (TT), and often look there. It has one gap, though; it often doesn't show current sources for interesting varieties, which I may or may not be able to find elsewhere. For example, I'm interested in trying Rozovyi Myod for reasons have nothing to do with the breeding project discussed in this thread. TT lists seed availability through 2018, but nothing thereafter. I see some mentions of Rozovyi Myod (or more often, its translation as "pink honey") occasionally elsewhere, but am concerned it may not actually be the same variety.

William's comments about epigenetic activations for cold subsequently being deactivated points out a real problem with trying to breed a stable cold-tolerant line. I'm not sure what the solution might be.

After reading William's comments, I like the idea of getting wild genes into the mix through a blend that already incorporates S. habrochaites and S. pennellii, but is already crossed with cultivated tomatoes and palatable.

Steph S, I like the idea of standing on the shoulders of Russian breeders. Could you please give me a list of specific Russian varieties you would recommend as a starting point?  Some Russian varieties were likely bred for conditions down by the Black Sea, which would be completely different from something bred farther north. It's great to hear you say that cold tolerance crosses well into other varieties.

I'm not yet willing to accept the existing limits of cold intolerance in tomatoes, especially when wild relatives grow thousands of feet above sea level in what most be very cold climates. I hold up beans as a comparison. I can get green beans for a longer growing season than I can tomato fruits, even though beans have no frost tolerance either. Beans grow faster, produce edible beans sooner, and continue to produce beans right up through first frost. They will usually survive a frost or two covered and continue making beans even when nights are cool. What would be the equivalent for tomatoes?

Ultimately, my goal is to get fresh tomatoes over a longer growing season. Right now, I am getting maybe 2 months of tomatoes at best. My goal would be to get them for about 4 months, taking into account effects of early starts indoors, perhaps cold frames outdoors in spring, row covers late in the season, and so forth. I'm willing to trade off taste for this, perhaps breeding taste back in at a later time.

That could be done through a mix of early tomatoes (which are able to sprout early, tolerate a late frost without dying even if they are set back somewhat, produce fruit quickly for early use in spite of cool (but not frosty) nights, produce fruit all through the hot summer, continue to set fruit when nights are below 50F and days are warm but not hot, survive early frosts under row covers, and finally end the season.

This does not have to be done through a single variety, and probably can't be. It could be a landrace with a wide range of genetics, or several homozygous varieties producing early, mid, and late tomatoes.

For breeding stock, I'm now thinking something like:

   Cold tolerance: Sub Arctic, Siberian, Lofthouse Wildling, (other Russian varieties?)
   Wide genetic range: Sungold F1
   Taste:  Black Cherry
   Disease resistance: Suggestions?  Is it needed since I have not had significant disease issues?
   Early:  Bloody Butcher, Stupice

I'll continue to think on this.

William S.

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Re: Planning for a 2023 tomato breeding project
« Reply #6 on: 2022-06-18, 09:21:05 AM »
Stupice is an old standby here for earliness but it and Bloody Butcher didn't make it that high on my earliness list. I would reccomend for earliness: sweet cherriette, 42 days, forest fire, anmore dewdrop, coyote, Jagodka earl's strain, terrior seeds galapagos cherry, silvery fir tree, and the tomato Joseph calls Brad and it's descendents. I suspect that earliness will be different for each of us in far apart climates. Therefore I reccomend trying a lot of early varieties to find out which does the best for you. I suspect you will find existing earlier tomatoes I sure did. Some of my own lines have occasionally performed very well in this regard under specific conditions such as amongst direct seeded plants. I also finally have a cross maturing with sweet cherriette.

I definitely love exploring the Russian varieties. One of my favorites is Krainiy Sever. I successfully direct seeded it in 2017, it was early, and it keeps the fruit off the ground because it is a determinate dwarf.

Don't be too disheartened about epigenetics. If you happen to activate something it should stay on a few generations and keep staying active if the plants keep encountering the trigger. I.E. it goes away when grown in say mild climates. 

I breed with Sungold F1 and descendants they are good for earliness and flavor. Blue Ambrosia a sungold and antho descendant was a early mainstay of my projects that led to a tomato I called exserted tiger and shared with the world through Snake River seeds so other people could use it. It is basically a vehicle for stripes, exsertion, anthocyanin skin, and somewhat short season.

For cold tolerance I am uncertain I have a few I've been investigating but it just seems like most tomatoes do OK for me as long as they are around 75 days to maturity or sooner. I have a specific accession of Solanum habrochaites I obtained for this but it was killed by a severe frost last year. Our nights can be cold here but not cold enough that I don't get seeds back on varieties that don't have this or at least aren't known for it.

I would also reccomend coyote, amethyst cream, and terrior seeds galapagos island tomato for flavor. I am in the first generation of trying to isolate good flavor from the promiscuous project. I am trying some new tomatoes this year for flavor specifically. Including I am growing Black Cherry for the first time.

Disease resistance is out there, I am dabbling with it but frost is my disease so far. I am intrigued by Galahad F1, Purple Zebra F1, and have obtained a couple wild accessions to target specific disease problems. If we who dont have it get hit by a disease I think it's important to note that you'll be able to cross your favorite projects with disease resistant lines inside over the winter. Also it is possible to grow an F1 and get to a variable F2 inside over the winter. Might be good to obtain some disease resistant seeds just in case but not a necessity if frost and cold are your primary opponents as they are for me.


Western Montana garden, glacial lake Missoula sediment lacustrian parent material and shallow 7" silty clay loam mollisoil topsoil sometimes with added sand in places. Zone 6A with 100 to 130 frost free days

Adrian

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Re: Planning for a 2023 tomato breeding project
« Reply #7 on: 2022-06-18, 02:29:37 PM »
 Do you think a dwarf tomato is a good idea for improve the earliness?

William S.

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Re: Planning for a 2023 tomato breeding project
« Reply #8 on: 2022-06-18, 03:09:01 PM »
Do you think a dwarf tomato is a good idea for improve the earliness?

With Krainy Sever I saw evidence that both dwarf and early is possible but I don't think dwarf itself is going to improve earliness. An early dwarf might. I see the advantage more in the sturdy stem since I don't provide support. So not incompatible but two different things.
Western Montana garden, glacial lake Missoula sediment lacustrian parent material and shallow 7" silty clay loam mollisoil topsoil sometimes with added sand in places. Zone 6A with 100 to 130 frost free days

William S.

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Re: Planning for a 2023 tomato breeding project
« Reply #9 on: 2022-06-18, 03:13:40 PM »
We don't have the sames climates and maybe not the sames varietys but we have harvested our first tomato the 1st september the last year It was the varietys san marzano lungo, andine cornue and canestrino di lucca and costoluto tasty but too  late.My idea was to found more early tomato. bloody butcher is the most early for me!
Most early than morettino.
San marzano lungo was the most productive the last year.
Someone has offer  F2 of tiny tim x green velvet. I think i can have early and tasty tomato.
I think more and more to try cross with bloody butcher.The first bloody butcher is mature today this year!
Do  you think its a good idea to cross bloody butcher with dwarf tomato  (tiny tim x green velvet f2)for increase earliness.

Have early tomato is even usefull for us in france.
I think for harvested tomatos the most long time it important to have differents earliness.
A small test for have more early tomato was to did the cross san marzano lungo x costoluto but the F1 is weak.
Maybe if i select F2 i can have a correct result.

I think taking things to the F2 and maybe even to the F3 is a good practice sometimes the early generations dissapoint but that doesn't mean we should discard a project. The genetics need time to segregate.
Western Montana garden, glacial lake Missoula sediment lacustrian parent material and shallow 7" silty clay loam mollisoil topsoil sometimes with added sand in places. Zone 6A with 100 to 130 frost free days

Steph S

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Re: Planning for a 2023 tomato breeding project
« Reply #10 on: 2022-06-18, 06:11:48 PM »
With regards the Russian/Eastern European varieties, I would advise you to trial as many as you can, to decide which ones you like as parents for your environment.   In choosing plants to trial I always had to limit my choices to 80 days or less aka "midseason" varieties at latest, but these latest ones were always crossed with earlier parents for a better fit for our season.
It isn't always easy to decide which plant will make a good parent.  Some crosses I made from tasty parents ended up shelved after a couple of generations, because the fruit wasn't tasty.  So the advice I would give you is to make lots of crosses, and see which lines are really pleasing to you.
There's a huge variety of tomatoes in that geographic region, and you can find quite early and cold tolerant lines of all shapes and sizes and colors.  So it depends on your goals, what size and shape you intend to aim for.

As for sourcing seeds, I would say you should drop in and join at Tomato Junction sometime before the fall, and join in on the MMMM swap.  There's usually an Eastern European category there, and you'll end up with lots to trial.  If you're looking for specific varieties, folks will help with that too.  Our friend Shawn is also in Vermont, and he's been curating and distributing the seeds from Carolyn Male's collection for several years now.  There were lots of Eastern European varieties included, and since they had all been pre-screened by Carolyn you pretty well could be assured there was something special about each one.  And Shawn can tell you how they grew for him in VT.  So you can get a great start on tomato material to trial in that seed-sharing community.  Many many more varieties than I personally have grown.


William S.

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Re: Planning for a 2023 tomato breeding project
« Reply #11 on: 2022-06-18, 08:50:46 PM »
That trade deal at Tomato Junction sounds fun but I overdid it a little last winter with tomato trades and acquisition, and I don't think I've done them justice. I think I would not be able to manage hanging out on another forum! I grew the ones I got last winter but some ended up crowded. I don't know how folks with really big tomato collections do it.

One key component of breeding is trying and or trialing what is already out there, and it is always possible that the perfect tomato for your needs already exists what with thousands of varieties available in the world. I think I have tried maybe a couple hundred.

I want to try more but I also really enjoy the variation that has arisen in my own garden as well as the variable populations other plant breeders have shared with me. Like Joseph's promiscuous project has been quite the experience growing this year and the prior four or five in its various iterations.
« Last Edit: 2022-06-18, 08:59:24 PM by William S. »
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Joseph Lofthouse

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Re: Planning for a 2023 tomato breeding project
« Reply #12 on: 2022-06-19, 12:01:23 AM »
Tomatoes are a tough species to use for breeding in frost/cold tolerance. Because they are from low elevation in the tropics, near the ocean. There just isn't any need for the species to have frost tolerance. Then to make matters worse, 95% of the available genetics were left behind during domestication and heirloom preservation inbreeding, which means that there is trivial genetic diversity from which to select. It's really tough to make any sort of meaningful advancement breeding only with domestic tomatoes.

A decade ago, I did a careful frost/cold tolerance trial with varieties that were highly recommended. They were mostly a disaster. None of them were frost tolerant. Jagodka, a Russian variety,   set fruit at low temperatures, and matured them in the cold. The region where it was developed is a low elevation, maritime climate: Coolish weather both night and day. Few Growing-Degree-Days are available.

Even the wild species from high elevation (such as solanum habrochaites at 11,000 feet), rarely experience much cold. Sure, the ancestors of the Beautifully Promiscuous and Tasty Tomatoes project survived frost, snow, and cold weather for a couple months after the domestic tomatoes died. I haven't restarted the cold/frost tolerance trials after making the crosses. Wildling, Q-series, Big Hill, and anything from the panamorous of polyamorous lines are descended from Solanum habrochaites, and Jagodka. Silvery Fir Tree was another ancestor.

I may restart the frost tolerance project, after I get a population of tomatoes that can be direct seeded.  I'm generating high enough volume of seeds, that I could throw 10.000 seeds at a frost tolerance project.

Steph S

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Re: Planning for a 2023 tomato breeding project
« Reply #13 on: 2022-06-19, 04:13:59 AM »
I absolutely agree that you should work with the wild relatives crosses to pursue frost tolerance.   

There's a general principle that is useful, when you want to produce a trait beyond the scope of the current parent pool, and that is to make as wide a cross as possible, meaning the parents are as far from closely related as possible.   When you work with wild relatives or their descendants, you are really maximizing that.

My own limits in breeding are just that, limits due to an extreme climate and having to grow in limited greenhouse space, with the additional limit that I have to produce a food crop at the same time.  So that is why I haven't pursued the kind of tomato projects which are possible with ample outdoor growing space.   I've tried to make my crosses as wide as I can by choosing parents from different continents, and also stirring the pot by making crosses between unstable generations.  And I've added stressful conditions to the breeding sometimes, by making crosses late in the season when conditions are already suboptimal.  IDK if that helped, my plants are always subjected to stress from the get go in any case. ;)

Cathy A

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Re: Planning for a 2023 tomato breeding project
« Reply #14 on: 2022-06-20, 08:14:56 AM »

From my reading, I've come to the same conclusion as Joseph Lofthouse. Getting true frost tolerance in tomatoes is going to require getting wild genes in the mix, and even then it's a low probability that may require the widest possible set of wild ancestors. Throwing 10,000 seeds from the most diverse possible lines at frost seems like the right approach, but it's beyond my own capabilities due to limited space. It may require new mutations to occur, which again means large plots with as many plants as possible.

However, my key objectives could probably be achieved by breeding a line or lines that develop fruit early, grow quickly in cool weather, continue to set fruit in cool weather as fall approaches, and can survive significant frost under a heavy row rover or temporary hoop house, even if they don't have actual frost tolerance. I've found that just about any tomatoes will survive a light frost here under a heavy row cover.

I don't see many serious amateur tomato growers growing them outside in zone 4 or colder, at least not in North America. Many grow them in a greenhouse, or in warmer climates zones 5 and south. So I don't think much work has been done on creating the most productive lines for cool weather here. Russian and nothern Europe may be different.

The varieties I've seen suggested on other sites or forums for these conditions tend to still require significant heat, and have been bred for a short warm/hot season rather than actually thriving in cooler conditions. (By contrast, I know one gardener in Canada who can't grow tomatoes outside because it isn't warm enough most nights in the early part of the summer to set fruit (below 50F), with very few nights staying above 50F, then she sees her overnight temps drop very quickly in late summer so still can't set fruit. Short-season varieties don't help her if they still require that nights stay above 50F.)

So I'm looking for cool climate tomatoes that aren't just faster from transplanting to producing fruit, but will grow and thrive in cool weather, and continue to set fruit when days are warm and nights are cool. None of this requires actual frost tolerance, though it would be nice to have.

I plan to do a mix of hand-pollinated hybrids across many of the starting varieties along with allowing some to self-pollinate.

My updated list for first-year genetic material is:

  Sweet Cherriette
  Forest Fire
  Big Hill (Jagodka cross from Lofthouse)
  Coyote
  Black Cherry
  SubArctic Plenty
  Siberian
  Sungold F1
  Lofthouse Wildling
  Glacier
  Kimberely (optional)

I can't test and cross too many varieties at once in my limited space, so new material may be added in year 2 in addition to hybrids from the year 1 material. Does this list seem like a reasonable starting point? Ten varieties with 2 plants each is a reaonable number of plants, though it won't be practical to do every possible cross (90 options even without Kimberely!)