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Post by Joseph Lofthouse on May 9, 2011 14:41:57 GMT -5
Breeding a Perennial Tetraploid WatermelonAbstractI am attempting to create a perennial tetraploid watermelon. The watermelon genes will be provided by Citrullus lanatus, and the perennial genes will be provided by Bryonia alba, a common winter-hardy plant that grows wild in the nearby mountains. The two parents are closely-related species of different genera in the same sub-tribe: Benincasinae. Even if the inter-generic cross is unsuccessful the breeding project is expected to produce an open-pollinated open-source tetraploid watermelon. DiscussionThe breeding program is being conducted in Northern Utah in a high altitude garden with a short growing season. Locally adapted watermelon will be used. Bryonia alba was selected as a parent because it is a winter-hardy closely-related perennial that grows in the surrounding mountains.
The chromosome number of cultivated watermelons is 2n=22, and the chromosome number of B. alba is 2n=20. This would be expected to create incompatibility problems if the two species were directly crossed with each other. A direct cross will be attempted, with little expectation that it will be fertile. It is expected that the incompatibility issues would be lessened if the parents were first converted to tetraploids and then crossed with each other.
Seedlings will be treated with Oryzalin which is a readily available pre-emergent herbicide that when used in small quantities can be used to convert diploid plants to tetraploid plants. MethodSeeds will be germinated in a warm environment for a few days until the root is about an inch long. The growing tip will be immersed overnight in a dilute solution of Oryzalin. The seedlings will then be planted in soil and evaluated by phenotype for tetraploid characteristics. Untreated controls will also be grown. Treated plants with diploid or chimeric characteristics will be eliminated from the program.
The extremely dilute Oryzalin solution will be created from off-the-shelf herbicide containing 40% Oryzalin by dissolving 1ml of herbicide in 100 ml of water and then adding 3 ml of that solution to one Liter of water. This is expected to produce a 10 PPM solution of Oryzalin.
Watermelon plants that appear to be tetraploid will be offered for grow-out to interested collaborators. The seeds returned by collaborators will be grown out to evaluate ploidy levels, fertility etc... (Collaborators could also conduct the second year grow-out and evaluation.) The watermelon lines that appear to be high fertility tetraploids will be developed into an open-pollinated open-source tetraploid watermelon.
A short study will be conducted to evaluate optimal conversion conditions.
B. alba tetraploid plants will be grown in-house.
After relatively stable high fertility tetraploid lines have been developed for these two species they will be cross pollinated and evaluated for desirable agronomic and culinary traits including winter hardiness and a perennial root system. The fruit of B. alba is extremely bitter. Selecting for non-bitter fruits will be a high priority.
CollaborationSend me a personal message or email if you want to help and are able to grow one watermelon seedling in the usa in 2011 in relative isolation from other watermelons. In later years collaboration will be done via seeds. ------------------------------------------------------ I invite feedback. I'd welcome collaboration if you are able to grow one (tetraploid, hexaploid, chimeric, polyploid) watermelon plant that is isolated by a couple hundred feet from any other watermelons and return some seeds to me if it produces any. A critical data point for evaluating each plant would be the number of fruits produced and the number of seeds per fruit. After I get comfortable with the conversion process I may attempt to make a tetraploid watermelon landrace, but for simplicity starting out I'm going to focus on a variety for which I have plenty of seed. Regards, Joseph
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Post by michedealseriana on May 12, 2011 12:38:23 GMT -5
Your project is very interesting.
However, I knew that Bryonia alba is poisonous.
Don't you risk to obtain poisonous watermelons?
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Post by Joseph Lofthouse on May 12, 2011 13:27:23 GMT -5
Your project is very interesting. However, I knew that Bryonia alba is poisonous. Don't you risk to obtain poisonous watermelons? The poison in Byronia alba is a well behaved poison. It tastes exceedingly bitter and nasty to humans. It will be easy to differentiate which plants are poisonous. I'm not looking forward to tasting so many nasty melons though. Perhaps I can find a paper chromatography step to identify the poisonous plants. Perhaps the most poisonous plants could be eliminated by smell. Also in watermelon the bitter (poison) gene is linked to the red color gene, so I'm expecting that by selecting for red flesh color I will be selecting against poison. The poison gene is dominant so it should be easy to eliminate. The red color gene is recessive so again it should be easy to select for in the F2 and later generations. If a direct cross doesn't work, and I end up making a tetrapoid that complicates the selection process to have so many possible dominant/recessive/co-dominant genes running around, but I guess that just means I plant more individuals so there is more variety to select from. Perhaps I won't be able to eliminate the poison. Then I'll fall-back to creating and sharing an open pollinated tetraploid watermelon. |
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Post by Joseph Lofthouse on May 13, 2011 23:12:44 GMT -5
On Tuesday I started germinating some watermelon seeds. They were ready for the Oryzalin treatment tonight:  So I made up an exceedingly dilute solution using 8 cents worth of oryzalin, and then I threw away 99.9% of what I made. Instead of diluting with water I used a solution containing 1/2 teaspoon of hypo-allergenic dish soap per quart of water.  Then put the seeds in a test tube holder with the roots upwards:  Then added some solution to just cover the growing tip, about 10 drops per seed:  Then put a damp towel over them, and put them in a plastic bag, and put them back in the dehydrator that's being used as an incubator (~90 F).  Tomorrow I'll take them out, rinse them, and pot them up. I ended up with 82 treated seeds and 5 controls. I'm thinking that since the bryony seeds are so tiny that I'll just germinate them for a few days then soak the whole plant in the solution, and then pot them up. |
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Post by keen101 (Biolumo / Andrew B.) on May 14, 2011 2:14:15 GMT -5
Certainly seems like an ambitious project, but the ambitious ones are always the most interesting. How will you know if it worked? (tetraploid). And assuming that the breeding with the perennial one does not work, how would a regular tetraploid watermelon be useful? Would that make it easier to cross watermelon with squash or cantaloupe?
On a slightly related note, I found a seed in a seedless watermelon the other day! It is my understanding that when a seed is able to mature in a seedless watermelon that it means that it either reverted back to a diploid, or is a tetraploid.
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Post by Joseph Lofthouse on May 14, 2011 4:07:41 GMT -5
How will you know if it worked? (tetraploid). And assuming that the breeding with the perennial one does not work, how would a regular tetraploid watermelon be useful? Would that make it easier to cross watermelon with squash or cantaloupe? I hear that tetraploid plants have thicker stems and more vivid colors than diploids.... If I wanted to get scientific I could count organelles under a microscope. (Maybe next year I'll attempt to turn Tom's orange diploid potato into a tetraploid. That might give him the deep orange color he's looking for.) An open-pollinated open-source tetraploid watermelon could be interesting because then we could grown our own seedless watermelon seeds. One strategy I read about is really clever. With careful attention to detail: They grow the seeds and melons, open-pollinated, and separate the melons at harvest time into seedless/seeded based on the color/patterns on the rind. I'm not contemplating doing crosses to squashes. On a slightly related note, I found a seed in a seedless watermelon the other day! It is my understanding that when a seed is able to mature in a seedless watermelon that it means that it either reverted back to a diploid, or is a tetraploid. Nice! |
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Post by johno on May 14, 2011 10:31:47 GMT -5
Canadamike supplied Alan, me and perhaps others with seeds for a tetraploid watermelon he called Tetra Baby. The idea was to use it as a pollen donor to make our own seedless watermelons. I was able to increase my seed count to 3  It has been a few years ago, and as far as I know, none of us have done much with it. I was unable to find the old thread. Maybe Alan or Michel can chime in here? |
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Post by raymondo on May 21, 2011 22:05:04 GMT -5
Does oryzalin act like colchicine?
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Post by Joseph Lofthouse on May 22, 2011 10:55:10 GMT -5
Does oryzalin act like colchicine? Yes. Effective oryzalin concentrations are 50 times lower than Colchicine concentrations. Colchicine is considered a "SEVERE health hazard" (the most hazardous category), while Oryzalin is considered a "Moderate health hazard". |
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Post by Joseph Lofthouse on May 23, 2011 16:08:14 GMT -5
No plants survived the treatment. Trying again with a more dilute solution.
Will also try another technique of dropping some solution directly onto the growing tip after seedlings have germinated.
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Post by terracotta on Feb 11, 2012 15:22:22 GMT -5
I am quite interested in perennial watermelons and therefore looked into this. Intergeneric crosses like this are the most difficult and only succeed typically with embryo rescue. If the two species did cross it would be similar to wheat crossing with corn where 2 to 5% of the offspring would be haploids of the maternal strain and the rest would be empty seed coats. The closest thing to a perennial watermelon I found was the citron melon growing wild in such places as California. Here it is regarded as a weed and not a pure citron melon because of frequent breeding with domestic varieties.
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Post by raymondo on Feb 11, 2012 16:35:37 GMT -5
Will you be trying again this season Joseph?
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Post by Joseph Lofthouse on Feb 11, 2012 17:13:02 GMT -5
I'm intending to try again this year. If I start earlier and do this indoors, I'll have more opportunities to get tetraploids. Last year I started too late: By the time my first attempts failed it was too late in the season.
About a week ago I collected more B. alba seed from a specimen/population that has been growing for more than 40 years less than a mile from my garden.
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Post by terracotta on Feb 12, 2012 18:03:49 GMT -5
I would suggest a pollinator for seedless watermelons because they can induce fruit set on sterile triploids. a good example is allsweet or sugar baby.
try to choose a variety as close to the phylogeny of citrullus lanatus like citron to b. alba
everything I have read said to dose the plant with oryzalin at the terminal bud for no more than 3 hours and not to treat the roots since the main mode of action is root necrosis
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Post by Joseph Lofthouse on Feb 12, 2012 18:54:37 GMT -5
Thanks. Citron lacks the winter hardiness that I am seeking. B. alba is a winter hardy perennial here, and is in the same sub-tribe as watermelon. There's that pesky extra chromosome though. By going the tetraploid route, I am mimicking what happened with Rutabega. Wish I could just find a short season tetraploid watermelon, then I'd only have to make a tetraploid B. alba. Oh well. |
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