Breeding: Perennial Tetraploid Watermelon

[Joseph Lofthouse]

Jun 20, 2012 16:17:50 GMT -5 @terracotta said:

how are you determining which are chimera?

I figure that if one part of the plant looks different than another part, then it might be a chimera. Twisted stems or leaves would be another clue.

The watermelon are not growing much yet, it's still very cold in my garden. We had frost again last night.

[Joseph Lofthouse]

Here is what the controls (diploid) looked like a couple days ago:


And this is what the presumed tetraploids looked like:


Don't read too much into the difference though. They are planted on opposite ends of the same field, so there might be differences in soil, and there are definitely differences in how irrigation water was applied, and in weeding, and in soil prep.

[Joseph Lofthouse]

I attempted to convert my daddy's subvariety of Charleston Gray to tetraploid this spring. The presumably tetraploid watermelons are growing more robustly and precociously than the diploids. These results are only preliminary, but it looks like there might be some utility in converting my watermelon breeding program to focus on an open pollinated line of tetraploids.

My cold tolerant watermelon breeding program was direct seeded into the garden. The presumably tetraploid and it's controls were transplanted.

Here is what the diploid controls looked like this evening:


And the presumed tetraploid looked like this: (A couple fruits about 5" long.)


I haven't measured plant parts, but one difference that is fairly striking in the field is the amount of hair on the stems. The difference in whiteness is not an artifact of lighting. It was startling to me because I don't normally notice that watermelon vines are hairy.

This is what the diploid controls look like:


And the presumably tetraploid plants look like this:



The plants are in the same field, but they were irrigated differently and weeded differently, so caution is advised when interpreting results.

The Bryonia Alba that I transplanted to my field didn't thrive, but I'll collect some pollen from other local sources.

[Joseph Lofthouse]

The leaf on the left is typical of my diploid control watermelon: My daddy's sub-variety of Charleston Grey. The leaf on the right is typical of the same variety that were treated in an attempt to convert them to tetraploids. Larger leaves are expected as a sign of a successful conversion.

[oxbowfarm]

Someone correct me if I'm wrong, but if you have a tetraploid and diploid watermelon, can you cross pollinate them to get some triploid "seedless" terminal cross seed? Or do the genetics also have to include other stuff like parthenocarpic behaviors to make a seedless cultivar work?

[Joseph Lofthouse]

Aug 11, 2012 6:47:22 GMT -5 oxbowfarm said:

if you have a tetraploid and diploid watermelon, can you cross pollinate them to get some triploid "seedless" terminal cross seed? Or do the genetics also have to include other stuff like parthenocarpic behaviors to make a seedless cultivar work?

The propaganda coming out of the seed companies is that seedless watermelon is an undertaking that is reserved for the seed high-priest and that it should not be attempted in the home garden. But, I think that you will certainly get seedless triploid watermelon regardless of which cultivars you convert to tetraploids, and which you use as the diploid. Some combinations might have a bit more residual seed-coat than others.

[ilex]

Aug 11, 2012 8:29:07 GMT -5 Joseph Lofthouse said:

Aug 11, 2012 6:47:22 GMT -5 oxbowfarm said:

if you have a tetraploid and diploid watermelon, can you cross pollinate them to get some triploid "seedless" terminal cross seed? Or do the genetics also have to include other stuff like parthenocarpic behaviors to make a seedless cultivar work?

The propaganda coming out of the seed companies is that seedless watermelon is an undertaking that is reserved for the seed high-priest and that it should not be attempted in the home garden. But, I think that you will certainly get seedless triploid watermelon regardless of which cultivars you convert to tetraploids, and which you use as the diploid. Some combinations might have a bit more residual seed-coat than others.

I believe the same ... you should get seedless watermelons. Hope you can do somes crosses and let us know. Maybe send a few to somebody in the real South to grow this winter.

They also say you shouldn't plant seeds from hybrids as they won't sprout or you'll get totally useless plants ...

[Joseph Lofthouse]

Today I attempted inter-generic crosses between Bryonia alba, and watermelon.

I attempted the following:

Tetraploid watermelon X B. alba
Diploid watermelon X B. alba

The B. alba is diploid. I didn't get a tetraploid cross made of it this spring. Also I collected the pollen from a wild plant. The root I transplanted into my garden this year is alive still, but it didn't thrive because I put it too close to a tree that wicks moisture away. When I went to my favorite B. alba patch, it had finished blooming for the season. Luckily it is common around here so I was able to find a patch in a different micro-climate that is just starting to bloom.

And then just to be a smarty pants:

I made the cross of [Tetraploid watermelon (gray) X diploid watermelon (striped)]. Based on how the sibling group is segregating, I think that the striped watermelon is heterozygous for striped fruit, so if the seed gives any striped fruits they aught to be seedless.

It took me a long time, because just about every watermelon blossom in the patch was male. Locating the first female blossom was difficult. But once I found the first then I knew what to look for and it was easier. (Anthers look frilly, styles look like a ball.) All of the female flowers I located were already opened, but I went ahead and used them anyway. I closed them up after I was finished.

The allegedly tetraploid melons are seeming really clever to me this year. There are dozens of fruits on them right now that weigh around 2 to 8 pounds. No fruit has set yet on the diploid controls.

[keen101 (Biolumo / Andrew B.)]

Interesting, i am curious to see if they are indeed tetraploid. Assuming that they are, this means that doubled genetics often created plants which grow better? If so, does this mean all tetraploid watermelons are preferable to diploid if they set fruit earlier in harsh and short season climates? I'm not interested in seedless watermelons, because i find the flavor to be lacking than the seeded varieties, but i find this experiment interesting nontheless.

[Joseph Lofthouse]

Aug 14, 2012 15:55:27 GMT -5 keen101 (Biolumo / Andrew B.) said:

Interesting, i am curious to see if they are indeed tetraploid. Assuming that they are, this means that doubled genetics often created plants which grow better? If so, does this mean all tetraploid watermelons are preferable to diploid if they set fruit earlier in harsh and short season climates?

The allegedly tetraploid melons might be doing better for environmental reasons, because my field is not uniform. The soil and water vary from place to place, and the weeding is different. But the conditions are approximately the same. The allegedly tetraploid plants are doing much better than any of the diploid watermelon plants wherever they are located in my fields.

I attribute this partly to the larger leaf size... A leaf that is 40% larger will collect 2X the sunlight that a smaller leaf collects. And since these plants have had larger leaves since they day they were transplanted into the garden, they have harvested 2X the solar energy all season long. Perhaps it causes some sort of exponential growth curve.

My plan for next year is to take the earliest fruiting plants from my diploid watermelon landrace and attempt the tetraploid conversion on them also. Taking a cultivar that is extra early due to genetic disposition, and giving it the ability to be even earlier by collecting twice as much sunlight would be really clever.

And while I'm at it, I might as well do a diploid to tetraploid conversion on my cantaloupe landrace.

[cortona]

Joseph if you have tetraploid seeds of your watermelons i'm really interested to try it here next year, being hearlier and adapted to harsh climate they will perform nicely here in spring and probably set fruit before the extreme heath cause the abrth of flowers and sometime the death of the entire plant

[keen101 (Biolumo / Andrew B.)]

And while I'm at it, I might as well do a diploid to tetraploid conversion on my cantaloupe landrace.

What would happen if you tried it on squash? Would it make long season squash do better? Seedless triploid squash?

[Drahkk]

OOOooo... tetraploid Costata Romanesco... Gunnera manicata with edible fruit?

MB

[raymondo]

That would be some zuke!

[terracotta]

this is typically done with grain for example wheat is tetraploid or hexaploid. find a good seedless watermelon take some seeds that will sprout and convert them to get hexaploids ( 3N to 6N).
These then will have viable seeds.

Thanks for the great resource Joseph. you could correlate growth results better if you do some internodal distance measurements. measure between leaf nodes, the larger the size the faster the growth typically do to nitrogen inputs (does not work for bush types).