Inbreeding depression tomatoes question

I've been told that with tomatoes, while you can easily re-sow seed from non-hybrid tomatoes, it is not advisable to do that over more than 3 or 4 years, to avoid inbreeding depression. Is this correct, and how do you keep vigour in home saved seed?

I have been saving my heirloom seeds for over 30 years.  We also plant a few other different varieties every year as well so maybe my heirlooms get some cross pollination.
Heirlooms have changed a little bit I think, maybe the shoulders of my cherokee purples are greener?  Maybe pink branywine are a little darker?  I have had not problems at all, that may be due to cross pollination. I do not isolate my tomato plants from one another.

When tomatoes were domesticated, they became highly inbred, losing 95% of their genetic diversity. Current growing practices continue to make them ever more inbreeding. Commercial and amateur plant breeders choose to inbreed new varieties for about 8 generations before releasing them. The confluence of these factors, has created a species that is among the most fragile that we grow.

Therefore, the hybrids and the heirlooms are highly inbred, and lack vigor, just because they are tomatoes. In general, commercially available hybrids produce 50% more fruit than heirloom varieties.

My answer to the original question, is that if you like a tomato you might as well not worry about inbreeding depression, because every tomato you grow is suffering from it in one way or another.

When I introduced promiscuous flowers, and wild genetics into tomatoes, it was an attempt to stop growing tomatoes that suffer from inbreeding depression. How does one change the meme surrounding how to grow the most popular crop in the world? One garden at a time. One naturally occurring hybrid at a time. One tomato at a time that has open flowers that invite cross pollination.

My project right now are micro dwarf tomatoes.   Crossing them to selected tomatoes that include dwarfs, determinates and indeterminates.  As you said once we get a plant we really like we then grow their seeds out for 8 generations  so they produce tomatoes that are all alike.    So yes the seeds that get sold for our new varieties are already inbred.  

On the other hand anything that I breed for my own garden can be as mixed up and wild as I want. Plans for this year include attempting to cross a couple of different micro dwarfs to Amish Yellowish Orange Oxheart.  This variety was among those tested by the  Heritage Food Crops Research Trust and it was found to have the highest levels of cis-lycopene  among all the tested varieties.   I was lucky enough to get the seeds for it in a seed swap and I am hoping to bring those genetics into a micro dwarf I can grow inside during the winter.  

I am growing a couple micro dwarfs this year. Should be a fun winter hobby but I will probably do something odd like cross them with Joseph's promiscuous project or a strain of Solanum habrochaites. Shouldn't after all my winter hobby be just as wild as my summer hobby?

Joseph Lofthouse wrote:

When I introduced promiscuous flowers, and wild genetics into tomatoes, it was an attempt to stop growing tomatoes that suffer from inbreeding depression.

1. Is there any way I can take a tomato flower that does not appear to be promiscuous and help it cross?

2. Am I likely to find variation in how open tomato flowers are on a single plant or on multiple plants?

Inspired by some of the discussions this week, and photos posted, I looked at a few of my tomato flowers yesterday, and I don't think the stigma is showing at all. Am I right that in promiscuous tomatoes, the stigma would show beyond the anther cone, and you would actually be able to see pollen, which I couldn't with the tomato flowers I looked at?

I don't get much sun or heat on my property, so I tend to only grow a few tomato plants with relatively small fruit as I've found the smaller fruit is more likely to manage to ripen. I would like to encourage some of my small but tasty breeds to cross, as I would like to feel they have lasting genetic diversity.

Biology is fuzzy. Flower type on a specific tomato plant may vary slightly due to growing conditions. In general, if a plant has small, closed flowers, all the plants on the plant will have the same type of flowers. If a plant has huge, open flowers, all the flowers will be huge an open, with some wiggle room for the fuzzy nature of biology. The variation of flower types between plants is much greater than the variation on a single plant. Variation in flower type between varieties, is much greater than the variation within one inbred (OP/heirloom/hybrid) variety.

People have been doing manual cross pollination of tomatoes for ages. If you cross plants from two highly inbred varieties, from a highly inbred species, you still end up with amazingly inbred tomatoes.

When I buzz pollinate the promiscuous tomatoes, or flick them with my finger, it's common for a cloud of pollen to fall out of them.

The stigmas of the promiscuous tomatoes might stick out of the anther cone as much as 1/2 inch. If they even have an anther cone.

Among the domestic tomatoes, some of the cherry tomatoes have an exposed stigma, making them more likely to cross.

I favor saladette and cherry sized tomatoes, because of early ripening and high productivity in my short/cold growing season.

In the promiscuous tomato project, we decided that an adequate selection criteria is for big, open flowers.

Thank you for sharing these photos and expertise. Wow, those promiscuous tomato flowers are beautiful.

I'll double up on that thank you! I think you've got many members and certainly me, paying much more attention to flowers.

Amazing news! I have one tomato plant which clearly has large, promiscuous flowers on it! A friend had asked me to start her a "Pink Berkeley  Tie Dye" tomato as she'd read they do well here and she recalled I had seeds (given to me sometime, somewhere, because people do that to me!) I had TWO seeds, they both germinated, and I have one and my friend has one. Her plant blossoms look just like regular, over-domesticated tomato flowers.

So next questions: 1. how likely is it that the promiscuous characteristic will show in this plant's offspring?
2. am I better to let it breed to itself in the hope of keeping that characteristic, or should I dive right in and hand cross it with a variety of small, dense tomato that I have?  

I'm definitely looking for small, dense tomatoes - small so they will ripen despite our cool nights and dense because tomato sauce is *really * useful for so many meals that my family loves. My gut feeling is to dive right in, but I'm interested in hearing other's opinions, too!

Why not do both?  After all I imagine there is more then one flower on the plant...  Bag a couple to get self fertilized seeds and emasculate a couple and use the pollen from the dense tomato on them.  Also make a reciprocal cross with pollen from your big flowered plant to the dense tomato.   That would give you 3 lines to grow on and see what they are like next year.  

This ==>

Joseph Lofthouse wrote:Biology is fuzzy.  

True, dat!

As I think Joseph and others have noted Re: Inbreeding Depression, for many of those species that naturally or through human intervention have been self-pollinated for many eons, the deleterious genes have largely been removed by selection.  That being said, a variety that is kept year after year *can* erode....genetically.....if one saves too few seeds or if one is not at least somewhat observant of the plant/fruit/veggie that they are saving seeds from.  I made that mistake with potatoes, which are clonal, but I was probably not doing the best job of saving good, healthy, sizable, disease-free stock.  After several years, the yield was dropping, disease was increasing, and overall a tipping point was reached where I decided to get new stock and start again....with a resolve for better diligence on what was being saved.

But also to say that "fuzzy" can be your friend.  Breeding and genetic 'accidents' are the raw material of improvement and delight, along with curious observation, for seed saving as clearly Joseph and others here demonstrate.

But also to say that "fuzzy" can be your friend.  Breeding and genetic 'accidents' are the raw material of improvement and delight, along with curious observation, for seed saving as clearly Joseph and others here demonstrate.

I am hoping some of that "fuzzy" will keep working with the line of micro dwarfs I am currently growing.  My inexperience showed this winter and I lost most of my starting plant but not before a couple had produced some to me extraordinary tasting tomatoes.  My current crop are all the seeds I had from one of those plants/tomatoes that I dubbed Steak Sauce.  My first bite of that tomato had me wondering how I had gotten steak sauce on it.    Fast forward I have 15 plants that I grew from seeds of that tomato.  3 currently have tomatoes on them that are ripening...  I can hardly wait to see if I got lucky and they  also have that flavor.  

On the other extreme this year I will be playing with whites with fruity flavors and one described as having a unique flavor.  Crossing them onto a pink micro dwarf with a very mild almost nonexistent  flavor that I described in my notes from last year as a bag of water inside a tomato skin...

Dorothy Pohorelow wrote: ..... a bag of water inside a tomato skin...

Ha!.....yeah, 'fuzzy' works in both directions, -- sometimes towards things we don't care much for as well as things we do.  :-)

What I'm fascinated with in regards to Joseph's and other's tomato project is the sudden flooding of ..... for example..... the USA germplasm pool with wild gene alleles.  (I don't think there's any risk of converting existing heirlooms or varieties if one does not wish it, but I'm thinking about those who will be picking up on those seed packets and making the resulting diversity more common to observe at a local farmer's market.)  Even gazing through some of the more prolific and diverse offerings in the catalogs in the mail at those different colors and sizes of tomato that have come largely from heirlooms and recent selections is tantalizing enough.  Beyond this, however, the wild alleles, although needing their own weeding through, must have some really fantastic colors, flavors, shapes, maturity dates, etc..  for observing and tasting.  It could signal a real renaissance of grass roots seed keeping and novel variety development.

Jay Angler wrote:

2. Am I likely to find variation in how open tomato flowers are on a single plant or on multiple plants?

The flowers early in the season are more likely to be open, or more open than they otherwise might be.  My first foray into seed saving, I saved only seeds from the earliest tomatoes and ended up with more crosses than I was expecting. I ended up losing some genetics I really liked, too🙄

John Weiland:

I have been releasing the offspring of my tomato breeding projects as soon as there is enough seed to share. In 2018, and 2019, I distributed about 5000 seeds, each year, to people who attended my presentations at national seed conferences.   In December 2020, I sent about 40,000 seeds to Experimental Farm Network for distribution. The flavors are like nothing that has ever been released before in a tomato. There are so many directions that people could take the population. Some of my collaborators are already releasing their work, or will be in the next couple years. Exciting times!

I'm not going to be working on developing red-fruited tomatoes, cause I think that the taste is horrid for fresh eating. Other people will develop those lines.

All it will take for the promiscuous tomatoes to take over the world, is for one population to have the right genetic combination to be immune to the blights that are so common among tomatoes grown in the damp climates of the eastern usa. Imagine a tomato that could be planted, and didn't need trellising, pruning, or sprays!!!

One of the ancestors of the promiscuous tomatoes receives it's moisture from fog in the Andes. That might be well adapted to damp growing conditions back east.

One of the promiscuous tomatoes grows as a small shrubbery. The leaves don't fall into the dirt.

I know a person in the Micro Tomato Diversity Project who is going to be trying his hand at bringing in some of those genes to his micro dwarfs.  He and another member have talked about making decorative micro dwarf tomatoes.   ie novel leaf types,  larger flowers, different colors in the flowers, etc.   as a way to attract folks who would never think of growing tomatoes.  

My goals are more about taste and ease of growing them both outside in summer and inside during the winter.   The group is set up similar to the Dwarf project so we have our projects plus if we want to work on the bigger group project we can.  I started last year by growing out F2 seeds from someone else (that is where Steak Sauce came from) and this year I will try some crosses of my own as well as continuing the grow outs from the F2 seeds I was sent.    I am learning so much :)