I understand the reason we want seedless watermelons – because of the big seeds, but seedless tomatoes? Do we really need them? Why would you grow them? If they don’t make seed, how can they be grown from seed? Are these some kind of new GMO franken-toms?
The story of seedless tomatoes is quite interesting and can teach us a lot about plants. In this post I’ll squash out the current knowledge about them and provide you with the background you need to make the proper choice when buying plants for your garden.
Why Do We Need Seedless Tomatoes?
When I first discovered seedless tomatoes I thought it was just another useless product, but there are some good reasons to have them and also some health myths we need to debug.
Many sites about tomatoes suggest that some people can’t eat the seeds because of a condition called diverticular disease, were seeds get stuck in the folds of the intestine. This is old and incorrect information. The medical references I found suggest that there is no evidence seeds cause this problem, ( also this reference and this one that explains diverticular disease well).
Some people have trouble digesting tomatoes, or are allergic to them, but this is the whole tomato, not just the seeds. I found no medical reason why anyone would benefit from seedless tomatoes.
The tomato juice and ketchup industry would benefit from using seedless tomatoes. The seeds just get in the way of processing the fruit and producing seedless juice.
What is a Seedless Tomato?
You might think that a seedless tomato is any tomato that does not have seeds in it, but it’s not that simple. There are a number of tomatoes that are considered seedless because they have very few seeds in them.
There are also tomatoes that produce 100% seedless fruit – some of the time. Usually fruit produced early in the season is seedless and fruit produced late contains small amounts of seed. The problem is that you can’t tell which is which until you cut them open.
Some tomatoes that have seeds that are not fully developed. You might have noticed this is so-called seedless watermelons that have small, white undeveloped seed. The same thing can happen in tomatoes and these types are usually called seedless.
There is also a true seedless tomato that does not even have small immature seeds.
Some Tomato Biology
The tomato – the part we eat – is a fruit. In biology, the term fruit is the part of a plant where the seeds develop. The seed capsules on flowers in the garden are also fruits even though they don’t have a fleshy part like a tomato or apple.
When a flower is pollinated, the pollen fertilizes the ovule (the egg) inside the ovary of the flower. Once this happens the ovule develops into a seed and the ovary develops into a fruit. The important point for this discussion is the fact that the fruit does not develop until the ovule is fertilized. In a normal plant, if there is no fertilization there will be no fruit.
If fruits develop only if seeds are forming, how do we ever get seedless tomatoes?
One way is to cross a diploid with a tetraploid to produce triploid (3 sets of chromosomes). If pollen from a normal diploid plant reaches the tetraploid, fertilization takes place, fruit develops, but proper seeds are rarely formed. This is the process used in some watermelons which produce small, white dysfunctional seeds. In order to grow these in the garden you need some normal plants (the diploids) growing beside your tetraploids.
This may work well for watermelons, but most tomato flowers are fertilized with their own pollen, either by bumble bees or by wind. This explains why different heirlooms can be grown quite close together without contaminating the lines. A mix of both diploids and tetraploid tomatoes would be mostly self pollinated producing few seedless triploid fruits.
There is another condition in plants called parthenocarpy. Such plants have one or more mutations that allow fruit to develop even if there is no fertilization. In tomatoes, one such mutation increases the auxin level so that fruit is produced with no fertilization.
Low Seed Tomatoes
Low seed tomatoes have been around for a long time and many of these are heirloom tomatoes. These varieties produce a small number of seeds but are not really seedless.
The paste tomato is an example of this. Over many years people have selected a tomato that is very fleshy and dry. In the process they have also selected for a low seed count.
Over the years people also found other types of tomatoes with few seeds and preserved them as well. The following are some of the cultivars that claim to have few seeds. In my casual reading, it seems as if the actual seed count depends on where the plants are grown, and maybe even the purity of the seed line. Not everyone reports low seed count for these varieties.
Some varieties that are reported to have low seed count include, ‘German Pink’, ‘Valencia’, ‘Ashleigh’, ‘Amish Paste’, ‘German Johnson’ and ‘Gold Nugget’. My friend at Seeds of Imbolc has also suggested; ‘Sicilian Saucer’, ‘Marizol Gold’ and ‘Italian Heirloom’.
Almost Seedless Tomatoes
Dr. James Baggett from Oregon State University did a lot of work to develop new varieties of vegetables that produced earlier in the cool Oregon climate. His work in tomatoes resulted in several almost seedless tomatoes.
What is the connection between producing fruit in cold climates and being seedless? One of the consequences of parthenocarpy is that fruit development does not need to wait until warm temperatures for proper fertilization. Fruits develop as soon as flowers are formed. So selecting for fruit development in cool conditions indirectly selects for seedlessness. Many of Dr. Baggett’s tomatoes are parthenocarpic.
Some of the varieties in this group include, ‘Oregon Spring’, ‘Santiam’, and ‘Siletz’.
The First Seedless Tomato
Burpee introduced a tomato called ‘Sweet Seedless’ around 2004 and they claim that it is the first seedless tomato. This appears to be an F1 hybrid but the details of the parents have not been made public. Unlike the heirlooms mentioned above, most people find that ‘Sweet Seedless’ is 100% seedless or very close to it.
Some of the promotion for ‘Sweet Seedless’, including Burbee, says, “And precisely because there are no seeds, all the sweetness goes into the fruit itself and is immediately available for you to enjoy”. That logic does not make sense. Just because seeds are not produced does not mean the tomato is extra sweet. In fact, reports on discussion forums indicate it has an average sweetness.
Interestingly, Burbee has been selling this tomato for more than a dozen years and yet they have not introduced other seedless tomatoes.
More Seedless Tomatoes
Once you understand parthenocarpy it becomes obvious that gene editing could be used to produce seedless tomatoes, and that is exactly what has happened. Keishi Osakabe from Tokushima University has used the gene-editing technique called CRISPR to produce flowers which contain high levels of auxin. These tomatoes produce fruit without being pollinated.
In order to grow these new tomatoes you would need to obtain cuttings. They can’t be grown from seed since the plants make no seeds.
In normal breeding it is a lot of work to migrate a new mutation into existing varieties, but not so with the CRISPR technique. Seedlessness could be easily added to any variety. This is one of the big benefits of CRISPR technology.
Since the fruit is developed without pollination, bees are no longer required. This is a benefit for closed areas like greenhouses, or in geographic locations that do not have enough wind or bumblebees to naturally pollinate tomatoes.
This research is very new and these tomatoes are not yet available on the market.
References:
- How Do Seedless Fruits Arise? ; https://www.scientificamerican.com/article/how-do-seedless-fruits-ar/
- Gene Editing Produces Seedless Tomatoes; https://www.newscientist.com/article/2127640-gene-editing-opens-doors-to-seedless-fruit-with-no-need-for-bees/
One word – Gastroparesis!
No mention of seeds in this post: https://www.mayoclinic.org/diseases-conditions/gastroparesis/symptoms-causes/syc-20355787
or https://my.clevelandclinic.org/health/diseases/15522-gastroparesis
They get under my false teeth
I’ve had diverticulitis and did not know about the seed thing. But, thinking back, I used to eat tomatoes all 3 meals a day, I just love tomatoes especially with black toast. 2 yrs ago I developed severe pain in my stomach and ended up in the hospital for over 4 months. They had to remove most of my intestins now have a pouch and now all seeds get caught under my wafer and then it starts to leak. So yes, seedless tomatoes would mean the world for me. Maybe then I would be able to eat canned tomatoes too in my meatless spaghetti sauce. I can do without the ground beef that gets under my wafer also , but my tomatoes I would just love them back.
False assumptions:
1. You state that anyone allergic to tomatoes must be allergic to the whole tomato. Wrong. The skin and seeds contain different chemicals. There are many people who can eat tomatoes without problem as long as the skin and seeds are removed.
2. You found no medical reason why anyone would benefit from a seedless tomato. Response: you didn’t look very hard.
3. “current medical thinking” on any subject is… subjective. For every doctor that believes one thing, there are researchers coming to different conclusions. However, new studies to be “debunked” and discredited until the data is so overwhelming that the AMA/FDA have to finally back down. Usually, by the time they do that (think their original fiery defense of trans-fats and their beliefs on fats and cholesterol) they try to claim that they, themselves, “discovered” the new science. So here’s the new fact that is out there but not yet canonized: people who suffer from auto-immune disease benefit from things like seedless tomatoes because the inflammatory properties of the skin and seeds of a tomato make them inedible (or at least not without huge consequences). Since auto-immune disease are on the rise, eventually doctors will join the rest of the world in understanding the role of inflammation. The’ll just take longer.
Re: #1: do you have a link showing that people are allergic to seeds? As I said in the article I did not find such a report. I never made a comment about the skin.
Re: #2: If it is so easy to find such a reference – why did you not post one?
in our indian folk knowledge,seeds of tomato are responsible for kidney stone in some people. i do not know how true it is . also in authentic old indian cooking, they used to remove tomato skins.
Upon reading this I discovered that I can’t take any of this information seriously because I am one of those people that cannot have tomato seeds or sesame seeds or any seeds for that matter. I have Diverticulitis and I find it awful funny that I always have a flare-up if I accidentally eat some tomato seeds or some sesame seeds. So bad so that I ended up in the hospital for two weeks having antibiotics pumped into me intravenously. But no I must be imagining things. Note the sarcasm.
I’m a full living proof that has a problem with seeds nuts and corn I can’t have it in any situation I have been in the er 2 times and stayed over night once because of the medical term diverticulitis. Seeds is another form of ways of getting stuck in the intestines that creates a hole pocket in them which I now have two of them inside me and yes seeds of any type weather big or small they will have a big impact in your health and in its digestive system. Whoever that says there isn’t any evidence your wrong in that assumption. Sometimes even as small as a seeds can get stuck in the intestines easily and can cause sever pain and it’s very discomfort and there is no medical treatment unless you go through surgery. That’s if you do survive from it.
I am looking for a seedless tomato for a reason not mentioned here. I have dentures, top and bottom, and like tomatoes. The problem I have is the seeds get under the denture, and it is excruciating. At the dinner table, I can’t really take my dentures out to remove the seeds! Another problem no one mentions is tough skin tomatoes where the skin seem to get rolled up under dentures.
Diverticulitis, in many cases, means avoiding most seeds.. tomato seeds in particular, set my diverticulitis off really bad. Strawberry, Raspberry, Blackberry, and Chilli seeds too, so have to be avoided at all costs. Though I can eat Blueberries, Kiwi and Sesame seeds.
Just because a medical journal doesn’t list it, doesn’t mean it’s not true. Berries have been my favourite fruits all my life, but since having diverticulitis, the closest I’ve got to eating Strawberries, Raspberries and Blackberries, is by making seedless jams every year. I stopped eating tomatoes altogether because once you’ve removed ALL the seeds, they’re mostly not worth bothering with. I would love, love, love to chow down on a bowl of strawberries and cream.. I’d LOVE to be able to wear a Blackberry smile when I take my granddaughter fruit picking.. but I can’t.. I have Diverticulitis.
Love this article! I’ve been an RN for 30 years. Medical references absolutely indicate that seeded foods do not contribute to diverticulitis episodes. I had been teaching this knowledge to patients for years…until I developed this condition!! For whatever reason, though medically disproved, I develop diverticulitis with any seed consumption. This is so, so sad, but true for me. I had finally accepted that tomatoes would not be part of my garden, until I read this article. Thank you so much for your insight! I will be attempting to purchase some seeds!
Your assumption and medical references regarding diverticulitis needs to be revisited! You obviously have never spent hours in the emergency of the hospital in such excruciating pain that morphine barely works because some seed got caught in your intestinal wall then became infected! Thus, people with different types of gastric problems steer clear of seeds – including tomato seeds. The seedless tomato provides so much pulp that it can be enjoyed without worry. Otherwise it’s a matter of cutting out all the pulp just to enjoy the outer skin. That being said, I really did enjoy reading your article, especially learning about parthenocarpy. Thank you for also including other suggestions for low seed tomatoes.
Pauline Martin
I am reporting what the current medical thinking is on the subject. If you have better references I would gladly have a look at them.
“Current medical thinking” is based on polls, not data. Half of those who have commented here described their own experiences. I favor research over anecdotal evidence, but the research has not been done. Anecdotal evidence, therefore, cannot be so easily dismissed. I can tell you that my worst bout last summer directly followed some wonderful cold drinks with a large number of raspberries.
https://iffgd.org/gi-disorders/diverticulosis-and-diverticulitis/nuts-seeds-and-diverticula/
We bought seedless tomatoes to grow.
“Current medical thinking” is based on polls, not data” – that is not true, and even polls are data when done correctly.