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Post by Joseph Lofthouse on Jun 23, 2014 13:09:54 GMT -5
The plants have to have matching pairs of chromosomes to be fertile, so if we double the chromosomes to make tetraploid parents, then the chromosomes of the offspring of the cross have matching pairs of chromosomes and may be fertile. Non-matching chromosomes gives sterile plants.
The tetraploid x tetraploid cross that I am contemplating is between two plants in the same sub-tribe: very closely related. At some point in crosses between different species I suspect that the differences become too great for the plant to function. Different families is probably too large of a difference. Different species within the same genera are a safer bet.
I suspect that this same sort of chromosome doubling technique could be used to make crosses between the different species of squash for example, but I don't think that a cross between grass and squash would be successful.
Extremely rarely the natural processes of plant reproduction function abnormally leading to the rearrangement of chromosomes and DNA and to the formation of new species. I believe that modern wheats arose by this process.
Alan Kapuler recommends growing different species of the same genera close together, because although successful crosses might be rare, they may still happen at low rates and may produce useful offspring. It's similar to the Aztec tradition of growing maize and teosinte close together.
If I make a diploid/diploid cross between plants with different numbers of chromosomes then the offspring will be sterile... Because they are sterile that requires me to convert the plant to tetraploid to restore fertility... The process of converting a growing plant to tetraploid is more difficult than converting seeds. It involves applying poisons onto the growing tip of the plant in high enough concentrations to make the conversion without killing the plant. The process creates lots of chimeric plants, dead plants, and unconverted plants. Converting seeds is a low cost and low effort conversion. Screening is simple. I have chosen the tetraploid X tetraploid route because of the simplicity. I can treat and screen the seeds in bulk. Going the diploid X diploid route would require me to treat each offspring as an individual leading to incredible labor costs.
The watermelon variety I started with was Charleston Gray. Very stable.
The B. alba that grows around here arose from a very small population and thus has a very narrow genetic base. It's probably not stable in the traditional sense of the word, but it is highly inbred.
I chose Charleston Gray because my daddy has stewarded a population for decades and at the time I started this project it was the only variety I knew that would reliably produce a harvest in my garden and for which seed was available in large quantity. If I were starting over today I would convert a different variety with more genetic diversity. Perhaps even a landrace.
It would have preferred to work with a European strain of B. alba with higher genetic diversity. I haven't attempted to convert the B. alba yet. I lost the seed. I found it a couple weeks ago, but put it in a safe place... Ooops. Because it is perennial I don't have to get seed from it the first year, the roots will overwinter. So I may still attempt that this growing season.
I think that garlic is mostly sterile because of chromosomal damage accumulated through eons of cloning. Creating tetraploids would not resolve the underlying genetic damage.
Big Ag uses these sorts of techniques to make seedless plants like grapes, watermelon, citrus, potatoes, etc. There is a big amateur hobby making tetraploid daylillies.
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Post by blueadzuki on Jun 23, 2014 16:23:43 GMT -5
Couple of questions of my own
If you DID get a triploid that had a characteristic you found worth saving, couldn't you use the colchacine (that's the spindle poison I assume you are using, as it is the commonest) to try and double it and get a hexaploid, which would be fertile again? and from there, couldn't you cross the hex back to a diploid and get back to a tetra (albiet a tetra with three copies from one parent and one from the other?
Actually, given the goal you seem to have, I'd think that would actually make more sense down the road (after you'd actually gotten di and tetra bryony/watermelon crosses), since presumably what you are trying to get out of this ultimately is a vine that has bryony's perennial roots, but is otherwise all watermelon in morphology, particualry in the "not having fruits full of bryonin" way (after all, what use would a pernnial watermelon be if the melons were actually poisonous)? I assume you are also hoping for a plant that has watermelon sized fruits, not byrony sized berries (bite sized watermlons might be fun, but given how much of the volume is rind, I doubt there'd be much food value in them.)
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Post by flowerweaver on Jun 23, 2014 17:15:31 GMT -5
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Post by Joseph Lofthouse on Jun 23, 2014 19:10:29 GMT -5
I originally chose Bryonia alba because it is closely related to domestic watermelon being in the same sub-tribe, and because it is extremely winter hardy here, and because it grows feral and abundant in the surrounding woodlands. I may eventually branch out to trying other perennial species that are not so closely related. I keep trying to grow Cucurbita foetidissima, which is a more distant relative with a perennial habit, but it hasn't germinated for me, or got lost amongst weeds or eaten by bugs/disease before reproducing. It is not winter hardy here. Based on it's phenotype, Texas Globeberry is more closely related to domestic watermelon than a lot of the other cucurbits. Citrullus colocynthis has the same chromosome number as domestic watermelon, and is a perennial in the same genus so it might be useful to someone in a warmer climate. It is not winter hardy this high up in the northern mountains. |
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Post by Joseph Lofthouse on Jun 23, 2014 19:30:46 GMT -5
Blueadzuki: I am using oryzalin as a spindle poison because I can buy it at the local nursery and it is less toxic to mammals. I hope to attempt to make the tetra melon X diploid B. alba triploid this summer. That would produce a plant with 2/3 watermelon background and 1/3 poisonous nasty B. alba. In theory a triploid could be converted to a hexaploid to restore fertility... It might make selection for non-poisonous fruit easier than with a 50:50 cross. Thinking about a hexaploid X diploid cross makes my head spin... I think that it would create (at least one unpaired chromosome), but the plant might eliminate the extra.... I suppose it depends on how complementary the two species chromosomes are.
Yup. A perennial watermelon isn't much good to me if it's inedible or takes too much labor to pick.
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Post by flowerweaver on Jun 23, 2014 20:05:40 GMT -5
How will you test potentially poisonous watermelons for their toxicity?
So, perhaps the Texas Globeberry would be useful in my locale if I wanted to breed a winter hardy watermelon?
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Post by blueadzuki on Jun 23, 2014 20:59:21 GMT -5
Blueadzuki: I am using oryzalin as a spindle poison because I can buy it at the local nursery and it is less toxic to mammals. I hope to attempt to make the tetra melon X diploid B. alba triploid this summer. That would produce a plant with 2/3 watermelon background and 1/3 poisonous nasty B. alba. In theory a triploid could be converted to a hexaploid to restore fertility... It might make selection for non-poisonous fruit easier than with a 50:50 cross. Thinking about a hexaploid X diploid cross makes my head spin... I think that it would create (at least one unpaired chromosome), but the plant might eliminate the extra.... I suppose it depends on how complementary the two species chromosomes are. Yup. A perennial watermelon isn't much good to me if it's inedible or takes too much labor to pick. Blueadzuki: Thinking about a hexaploid X diploid cross makes my head spin... I think that it would create (at least one unpaired chromosome), but the plant might eliminate the extra.... I suppose it depends on how complementary the two species chromosomes are. Yup. A perennial watermelon isn't much good to me if it's inedible or takes too much labor to pick. Actually, it usually doesn't, at least for a case where the actual set is the same, i.e. where all you are playing around with is the ploidy (which presumably will be the case for you post hybridization unless the cross's genes mutatate REALLY fast (to the point where it goes from behaving like a 6x to behaving like a 2x in one generation) crossing two plants of differing ploides gives and offspring with the average of those ploides. Odds are sterile, evens are usually fertile. 6x x 2x =4x crosses are done pretty often, as are even wider differnces (there are 5x, 7x, 9x and higher ploidy plants) Hexplods aren't really all that uncommon. Most commecial Stawberries are hexaploid as is pretty much all modern wheat (i.e. everything beyond emmer which is 4x and einkorn which is 2 [sort of]). actually that is a good question. Will you go chemical assement, or do that "taste it and if it burns spit it out" thing (I actually don't know how toxic bryonin is so I have no clue if the taste thing would be safe for them). And since melons cross on thier own, would a taste of the maternal tissue of the fruit really give you an accurate assement of the qualities of any of the seeds contained therin? There's almost an argument to the idea that, when you finally find a cross that meets your needs (right kind of root system, fruit with desired safetey and flavor) to take cuttings and propigate it vegitatively, so as to get some colnal siblings to intercross and give you "pure" seed of what you want. |
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Post by imgrimmer on Jun 24, 2014 7:16:52 GMT -5
Joseph Lofthouse, are you interested in european Bryonia alba seeds? It is a common plant, not to say weed around here. In some week there will be plenty of seeds.
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Post by Joseph Lofthouse on Jun 24, 2014 13:22:17 GMT -5
Joseph Lofthouse, are you interested in european Bryonia alba seeds? It is a common plant, not to say weed around here. In some week there will be plenty of seeds. I can't ask for them. And I can't be held responsible for unsolicited birthday cards that people send to me... I'd feel happy about birthday cards from Europe. |
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Post by Joseph Lofthouse on Jun 24, 2014 13:34:26 GMT -5
flowerweaver: I'd test potentially poisonous watermelons for their toxicity in the same way that I currently test other poisonous cucurbits like cucumbers, pepo squash, and melo fruits. Cut it with my knife, put a hint of juice on my finger, wipe it off, then lick my finger. One nice thing about cucurbit poisons is that they are well behaved and bitter as I have ever tasted. The thing about casting a wide net looking for new genes is that from time to time some of the poisons from the wild strains are reintroduced into the population.
With B. alba I might be able to smell the poison without actually tasting it. I don't know if I have skin that is sensitive to the toxin, but some people do. The lethal dose is said to be around 40 berries (unconfirmed Internet myth), but I need less than 1/100th of a berry for tasting, so I could taste 40,000 berries before I croaked. I'm unlikely to grow more than a couple hundred plants at any one time.
p.s. Yes I actually managed to introduce poisonous melo fruits into my muskmelon patch. I abandoned the seed from that patch. Poisonous cucumbers and pepo squash are more common so I do regular screenings.
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Post by kazedwards on Jul 11, 2014 0:25:51 GMT -5
Any updates?
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Post by Joseph Lofthouse on Jul 11, 2014 8:01:00 GMT -5
Update: The allegedly tetraploid melons and the diploid control were planted into the garden a few weeks ago. They are getting watered appropriately this year. They have gotten established and with the hot weather are starting to grow fast. As previously noted the supposedly tetraploid melons have larger leaves.
I planted a round striped yellow fleshed melon in the middle of the patch. Hoping that this will produce some naturally pollinated triploid crosses.
Still haven't discovered the supposedly safe-keeping location where I stashed the B. alba seeds. Plenty growing in the nearby woods.
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Post by Joseph Lofthouse on Jul 27, 2014 17:04:20 GMT -5
Here's a couple of photos to show the huge leaves of the (allegedly) tetraploid watermelon compared to the control, which is the same variety which was not treated with the chromosome doubling chemical. Diploid Control: Paradise Utah sub-variety of Charleston Gray.  Tetraploid Melons:  It turns out that I have two patches of tetraploid melons growing this summer. I am going to allow the isolated patch to grow as tetraploids in order to preserve and increase the seed. The other patch was inter-planted with seeds from a fruit that had yellow flesh and green stripes. I am intending to remove the male flowers from the tetraploid melons in this patch so that they can be pollinated by the diploid melon and hopefully produce seedless triploid melons next growing season. |
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Post by nicollas on Jul 28, 2014 12:34:24 GMT -5
I'm a bit lost, so you may succeed to create a seedless watermelon by crossing your tetraploid with a diploid, but what are the step to make them perennial ? Thanks for the inspiring project  |
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Post by Joseph Lofthouse on Jul 28, 2014 20:22:55 GMT -5
I'm a bit lost, so you may succeed to create a seedless watermelon by crossing your tetraploid with a diploid, but what are the step to make them perennial ? Thanks for the inspiring project The seedless watermelon project is using germplasm from the perennial watermelon project, but they are otherwise unrelated projects. If seedless watermelons show up next year, it will be another indication that the conversion to tetraploid was successful. This has been a slow project... Too bad I, my family, and my landlords have so many personal foibles and struggles that have interfered with the project. The next step is to collect more seed from the wild perennial relative, which I expect to do towards fall. The seed I previously collected is still lost. Note to self. Separate the collected seed into multiple packets and stash it in several different locations. Then the collected seed should be converted to tetraploid. Probably stabilized/selected for a few years, then crossed with the tetraploid melon to see what emerges. After that who knows? Back-crossing? screening the segregating offspring to be non poisonous and perennial... I intent to try a watermelon X wild relative diploid-diploid cross again this summer, just to see what comes of it... I expect it to be a dead end but it might give an early indication of what to expect. Another related project that I would like to undertake is to convert one of the better diploid watermelons into tetraploid -- especially one with yellow flesh. It would be nice if I could find one to convert which has plain non-striped skin so that it would be easy to tell in the field which are triploid (if the diploid pollen donor is striped). |
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