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Post by starry on Jun 13, 2013 9:48:56 GMT -5
Any suggestions on how best to plant them for observing potential tetraploids and seed saving for the same?
I was planning on planting them into 2 freshly tilled 3ft x 30ft gardens that are about 30ft apart from each other.
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Post by Joseph Lofthouse on Jun 13, 2013 10:27:27 GMT -5
Any suggestions on how best to plant them for observing potential tetraploids and seed saving for the same? I was planning on planting them into 2 freshly tilled 3ft x 30ft gardens that are about 30ft apart from each other. I already screened the seeds, and sent you what I think are most likely to be tetraploid. (I didn't screen the seeds that I sent out earlier to other people.) I also sent diploid seeds so that you can have something to compare them to. I'd plant the diploid and then chop them out in a month before they start flowering. My plan is to plant seedlings about 1 foot apart in a row, so that I can screen them while they are small. Visual clues that I have come to think of as tetraploid traits are: - Quicker germination.
- Bigger leafs.
- Faster growth.
- Fuzzier leafs and stems.
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Post by Joseph Lofthouse on Jun 13, 2013 10:48:33 GMT -5
... does this mean all tetraploid watermelons are preferable to diploid if they set fruit earlier in harsh and short season climates? If the screening criteria that I'm using this spring are valid, then it appears that the two earliest fruits that I harvested last year were from non-converted diploid plants. |
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Post by gilbert on Feb 11, 2014 19:38:33 GMT -5
Any more news? I am really interested in this project. I would like to see this process used to create new vegetables out of wild edibles, as Carol Deppe suggests.
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Post by Joseph Lofthouse on Feb 11, 2014 19:51:29 GMT -5
Any more news? I am really interested in this project. I would like to see this process used to create new vegetables out of wild edibles, as Carol Deppe suggests. I had a crop failure on the tetraploid melons this summer. @#$%^& irrigation systems! A collaborator grew a successful crop and is returning seeds. [Thanks!] I have plenty of seed from the year before also. Several B. alba plants sprung up in the yard (it's a local weed) so I have a ready source of seed and flowers without having to run off to the woods. |
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Post by gilbert on Feb 11, 2014 19:55:54 GMT -5
A quick question;
Why do two tetraploid plants cross easier than two diploid? I can understand the point of doubling the chromosomes after a wide cross, but what is the advantage beforehand?
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Post by Joseph Lofthouse on Feb 11, 2014 20:22:04 GMT -5
Why do two tetraploid plants cross easier than two diploid? I can understand the point of doubling the chromosomes after a wide cross, but what is the advantage beforehand? I'm speculating that doubling the chromosomes before doing the wide cross is easier: For me, with my crude methods, and philosophy towards growing things. Because I can attempt the conversion to tetraploid, and get stable lines that reproduce normally, thus cleaning up the damage caused by the doubling chemicals before attempting the wide cross. The cross might take care of itself by means of my natural pollinators so all I have to do is plant them close together and then screen for hybrids. And the cross might be fertile right off and produce gobs of seeds. Each step of the process is less muddled. If I attempt the diploid cross first, then my result may be plants which I have to convert, (the regular application of chemicals to a growing plant tip isn't my style), or (limited numbers of) seeds that I have to convert (but I won't have a clue how to screen for whether or not the conversion was successful). Just seems more confusing to me to go this route. |
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Post by Joseph Lofthouse on Jun 22, 2014 11:28:47 GMT -5
I'm still working on this project... Here's what the (purported) tetraploid plants look like compared to the diploid of the same variety. The tetraploid seed was grown out for me by collaborators due to crop failure of my planting. Also on this project, the wild parent for the wide cross planted itself in my garden last summer, so I don't have to travel to the woods to collect flowers for cross pollination. Last week I got some grafting clips. I figure that I'll try grafting the tetraploid melons onto the wild relative... There is some speculation that doing so may increase the chances of wide crosses being successful.  |
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Post by kazedwards on Jun 23, 2014 2:41:08 GMT -5
Ok so I just read this whole thread and I have a lot of questions.
A diploid has 2 sets of chromosomes, a triploid has 3 sets, a tetraploid has 4 sets right?
How can a chemical change the amount of chromosome in a cell? Broad question I know.
If the chromosome amout changes would it technically be a mutation?
Why do you want to convert it to a tetraploid at all? Couldn't you just attempt a diploid cross and still get a perennial watermelon?
Wouldn't you have the same problem trying to cross a tetraploid as you would a diploid? 20 chromosomes to 22 for diploid or 40 chromosomes to 44 with tetraploid?
And what is significant about a tetraploid. Is it so you can cross with diploid and get triploid which would presumably be seedless?
Could you use the same process that you used to convert diploid to tetraploid on the tetraploid and get plants with 8 sets of chromosomes and so on?
I know that is a lot of question but I am very interested and crorious in this project. It has also opened my mind to a new way of thinking and also confused me about a lot things too.
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Post by kazedwards on Jun 23, 2014 2:46:09 GMT -5
Last question.... I think
What is a chimeric plant exactly?
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Post by philagardener on Jun 23, 2014 9:03:36 GMT -5
Great questions! I'll try to answer a few - others feel free to join in!
Yes, diploid plants have two sets of chromosomes; triploids, 3; and tetraploids, 4.
A chemical (and, yes, this can be a natural compound) that interferes with cell division can cause a diploid cell that has duplicated its chromosomes to fail in separating the two sets to separate daughter cells. The cell that results now contains two diploid sets of chromosomes - a tetraploid! Chemical treatments can also result in the incomplete/improper separation of the chromosomes to generate cells with too few or too many chromosomes but not complete sets. That condition is called aneuploidy. Plants often tolerate changes in chromosome number better than animals. An example of aneuploidy in humans is Down's syndrome in which an individual has an extra copy of chromosome 21, and many cancer cells contain abnormal numbers of chromosomes.
The term mutation generally is applied to changes that affect the sequence of the chromosomes (changes in DNA bases as well as events associated with chromosomal fragmentation and repair). These occur naturally at some rate; they also occur more frequently in the presence of certain chemicals (mutagens), radiation, or UV light - all of which damage DNA. (There are also broader definitions of mutation that include any changes in the genome, including aneuploidy, and an aneuploid may have distinct characteristics relative to the individual from which it was derived.)
Tetraploids often show improved vigor, stocky growth, heavier petals, more flowers. Many varieties found in cultivation have been selected for such traits and a number are tetraploids.
As you noted, crossing a diploid and a tetraploid can generate a triploid. That is interesting because the plant is viable but encounters problems making pollen and ovules for the next generation (hence seedless watermelons). This hybrid sterility may be one reason why plant genomes don't keep increasing (tetraploid, octaploid, etc.) although chromosomal doubling followed by chromosomal loss may be important in evolutionary time, resulting in new species.
Finally, chimeras are plants that are composed of cells with different genotypes. Many of the variegated plants found in garden centers are chimeras of photosynthetic (green) and nonphotosynthetic (white, due to a mutation) tissues. New chimeras arise spontaneously but the branch containing them must be propagated by cuttings to maintain the trait or it will be lost; also chimeras do not breed true because that unique mix of cells is not passed along to the next generation. (There are non-chimeric variegated plants, but that's another story.)
In our example, treatment of a seedling with a chemical that can double chromosomal number affects some, but not all, cells in that plant - so it is a chimera. Only the cells that give rise to flowers (more specifically, pollen and ovules) can pass on their genetic information. However, once a tetraploid line is established (so all the cells are tetraploid) it is no longer a chimera and will breed true.
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Post by Joseph Lofthouse on Jun 23, 2014 9:38:40 GMT -5
I prefer to think of a diploid at having one pair of chromosomes, and a tetraploid as having two pairs, and a triploid as having a pair and an unmatched set.
When a plant is growing the DNA pairs are pulled apart by thread like proteins called spindles. They are then duplicated and put back together. Chromosome doubling agents are typically called "spindle poisons" and work by disabling the spindles.
In genetic science a mutation is typically defined as changing the sequence of the DNA base pairs. That does not happen during chromosome doubling.
Nature has very strong mechanisms in place to prevent plants with defective DNA from reproducing. One of those requirements is that in order to successfully reproduce a plant must have matched pairs of DNA. When crosses are made between species with different numbers of chromosomes that creates a situation in which there are unmatched sets of chromosomes. Those kind of plants might grow successfully, but they do not reproduce. (Seedless watermelon and seedless grapes for example). So I could make an inter-species diploid X diploid cross, and the offspring if any would be seedless. If some worthwhile offspring were found they could be reproduced vegetatively. It's my general policy to not grow sterile plants. A tetraploid X tetraploid cross would be fertile and allow the use of normal plant breeding selection methods.
Inter-species crosses between species with different chromosome counts are typically sterile. The chromosome number of the offspring is doubled to restore fertility. Turning a mature plant into a tetraploid is much more difficult for me than turning seeds into tetraploids and then crossing the tetraploids. Turning both parents into tetraploids first allows me to get stable and fertile lines before attempting the cross.
During the conversion process, the spindle poison works equally on diploid and tetraploid cells, so some other ploidys are likely produced. The growing tip of a plant is a cluster of cells, so if some cells are converted and others are not then we'd get a chimera: a plant with a mixture of both types of cells. tetraploid cells are typically larger and grow faster than diploid cells, so a plant that is a chimera manifests itself by having twisted leaves and stems.
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Post by nicollas on Jun 23, 2014 9:51:22 GMT -5
Happy that this project is still on your list, what a beautiful perspective  |
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Post by kazedwards on Jun 23, 2014 11:26:03 GMT -5
So then the advantage to a tetraploid watermelon is that it would have: higher fertility and increase vigor?
Would it be easier to make the cross with B. alba then treat the seeds and change to tetraploid to return fertility?
Why would a tetraploid cross work better than diploid?
Are B. alba and the watermelon variety that you are useing stable lines? Are tetraploids more adaptable to crosses with chromosomal differences in crosses?
Any luck with coverting B. alba to a tetraploid?
Could you convert from diploid to tetraploid (or double the chromosomal pairs) in plants such as garlic to return fertility?
Is this a common practice among plant breeders and big ag?
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Post by kazedwards on Jun 23, 2014 11:33:13 GMT -5
Can environmental conditions or otherwise cause this to happen naturally in plants without human intervention?
Plants from to different plant families have different numbers of chromosomes which is what makes them different right? So in theory you could take 2 plants from 2 different families, then double the number of chromosomes until they have the same number and then they could be crossed easily?
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