Diploid vs Tetraploid - a crossroads

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Plazbo
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Diploid vs Tetraploid - a crossroads

Post: # 67960Post Plazbo
Sat Jun 09, 2018 8:03 pm

I've been reading and gotten myself in a loop. I know there are people with far more scientific/technical understanding and familiarity here than I do so just looking for opinions/thoughts.

Being in Australia, a generally favourable climate except those few weeks or summer with 40C+/100F+ temps. I've been looking more at the warmer climate species and classes and well diploids seem the norm. Add in a lot of references to resistance to PM (something I've been getting a lot of....don't need Fedtschenkoana to make ghostly foliage here) and I'm left wondering what are the real pro/cons of diploid vs tetraploid?

IE
diploids = more frequent cross over
diploid = higher rate of expressing recessive traits
tetraploids = thicker parts

I would assume tetraploids have more complex/dense pigment and perfume simply due to cells having more going on in them.


Mostly just wondering why tetraploid dominates the work being done, may just be the whole "breeding back to the current best" thing at play but I feel like I'm missing something.

Thank you

Larry Davis
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Re: Diploid vs Tetraploid - a crossroads

Post: # 67964Post Larry Davis
Sun Jun 10, 2018 6:15 pm

My best guess, thinking of some other species that have been recently advanced by intensive breeding is that tetraploids have certain features that are advantageous in rapid reproduction/propagation for retail trade. Daylilies, iris, napa cabbage(which may have hybrid vigor being an allotetraploid) just pop into mind at the moment.

There is also what evolutionists call contingency. Kind of like an accident that send you down one road rather than another. Really most of the big breeding programs with roses have been in the last 150 years. How many generations is it from Austrian copper (or Persian yellow) to PEACE? The rose used to generate a yellow HT depended on HP background for repeat blooming. If the mutation of FLC happened in an ancestor of roses brought from China, what other choice of parent was there if one wanted repeat-flowering HT or HP roses? So despite being an impediment to getting homozygous FLC mutant which promotes free repeating, tetraploidy was about the only option. van Fleet made a triploid with diploid wichurana that certainly doesn't lack vigor. But repeated crossing and selection gives tetraploid offspring. Even fewer generations occurred between New Dawn (a sport) and most of the descendants.

Once there were some good colors, and good plant and flower form, competitive commerce drove the use of whatever could produce the fastest production of novelties, even before patents demanded it. Crossing the FLC mutation into diploids was very hard by classical genetic methods. It adds generations to the selection process.

Florist roses, pesticides, fungicides, fashions and styles constantly pushed work with the already well-positioned tetraploids to make novelties for teh insatiable market.

I hope someone can argue me out of this sort of fatalist position. Actually I'm optimistic that giving up pesticides and insecticides will drive the market in different directions. Plus application of CRISPR technology ought to soon allow us to get FLC mutants at will in diploid or tetraploid species. The issues are two. Actually doing it (selection), and successful plant regeneration. I would bet on floral dip being easier than callus tissue regeneration if we work with species that have large numbers of seeds per flower. Our stumbling block may be concern that the outcome could be labeled GMO.

Plazbo
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Re: Diploid vs Tetraploid - a crossroads

Post: # 67968Post Plazbo
Mon Jun 11, 2018 2:29 am

The end of the opening paragraph is a bit...questionable. Polyploidy for daylilies comes at a cost, significantly reduced seed set (often around 6 seed per tet cross but over 30 per dip cross) so advantageous reproduction possibly not. The flowers are generally more showy/larger/thicker with tets but both tet and dips are still intentionally bred, tet's don't do the Spider/UFO form well due to the thicker petals and pink (at least currently) works better in the dips. I can't really comment on iris too much, the bearded don't grow here well (they rot so easily), the non bearded classes (Lousiana, Pacific Coast, Siberbian,etc) are predominantly diploid though (there are a few tet lousiana and siberbian but they aren't the standard or where breeders seem to be working) but that market is far tinier...Tomas Tamberg has demonstrated some significant benefits in going tetraploid with non beardeds (fertile offspring from wide crosses, would open up warmer/humid climates than beardeds...just probably take a hundred years of breeding to look as equally interesting as beardeds currently are and to select for fragrance from the few non bearded species with it) but no one really seems to be working on that (possibly because it'd probably take more than 1 life time).

New Dawn seems to have been primarily bred back to HT's and a few Floribunda, can't really be surprised that tetraploid is the result, kind of an inevitability if always breeding back to tetraploid.

Between this and the other thread http://www.rosebreeders.org/forum/viewt ... =2&t=41594
I'm left thinking that tetraploid of the modern classes was more the result of breeding back to the best, chance and to retain cold hardiness (before the diploid cold tolerant species were considered) more than a significant advantages in being polyploid. I really feel like I'm on the outside looking in and something just isn't clicking in my head :\

On a slight tangent though, I would assume at least in part that FLC incorporates juvenile blooming? Do polyanthas, tea, china's, hybrid musks and noisettes (maybe?) not demonstrate juvenile blooming (I haven't really dug around in those classes enough to know).

donaldvancouver
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Re: Diploid vs Tetraploid - a crossroads

Post: # 67969Post donaldvancouver
Mon Jun 11, 2018 11:45 am

What is an FLC? Can we please define three-letter acronyms if we must use them? Thanks.
Zone 8, with warm dry summers, cool wet winters. Southern Gulf Islands, BC

Larry Davis
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Re: Diploid vs Tetraploid - a crossroads

Post: # 67970Post Larry Davis
Mon Jun 11, 2018 8:46 pm

Sorry for the acronym if that's the proper word. I wrote a long article on it in the newsletter a few years ago. It stands for Flowering locus C in the model plant arabidopsis. In roses it has a different name I suppose, but the principle is the same. When normal it allows flowering only after a winter. When mutated, the plant flowers as soon as it has the energy, so every few leaves up the stem. Probably the mutation was noticed only once and all the interesting (repeat-blooming) roses are descended from that once event. No real proof but circumstantial evidence. IN the wild the progenitors of various classes of roses do not rebloom. Only in the last roughly 200 hundred years have we in the west had them. That includes the existing CV of noisette, polyantha, china, tea and musk that do rebloom. To get repeat flowering in New Dawn offspring they had to be crossed to repeat-blooming plants, or multi-generation blind selection had to be used. Being market-driven, breeders took the shorter path.

About daylily and iris reproduction I meant vegetative, not sexual. Bigger sturdier, faster growing for cultured gardens, not survival in natural conditions.

Sorry, out of time for now. Off to tennis.

Larry Davis
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Re: Diploid vs Tetraploid - a crossroads

Post: # 67972Post Larry Davis
Tue Jun 12, 2018 8:55 am

To Plazbo. Yes you are correct. Tetraploids beget tets. So of course New Dawn x HT = tet. But if there had been reblooming dips, it would have given a lot of dips. It is my understanding that if one has a decent stable of dips and tets, one can make crosses to generate interesting trip offspring. And they are basically sterile so they become bloom machines. It has been commented on this board some years ago that some European breeders use that strategy to generate their most successful products. Certainly the KO roses are in much the same position re self-pollination, though I don't quite understand the cause of that self-incompatibility.

So we are always juggling different needs when breeding for the market. Working with low fertility triploids is a real pain when less than 10 % of pollinations yield seed. Either you need a lot of plants and a lot of people, or a lot of years per person to get something. But in most rose plants repeat blooming tends to shut off once there is a significant hip load, whether dip or tet based.

Pick your pain.

Karl K
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Re: Diploid vs Tetraploid - a crossroads

Post: # 68013Post Karl K
Wed Jun 20, 2018 12:28 am

Plazbo wrote:
Mon Jun 11, 2018 2:29 am
Between this and the other thread http://www.rosebreeders.org/forum/viewt ... =2&t=41594
I'm left thinking that tetraploid of the modern classes was more the result of breeding back to the best, chance and to retain cold hardiness (before the diploid cold tolerant species were considered) more than a significant advantages in being polyploid. I really feel like I'm on the outside looking in and something just isn't clicking in my head :\

On a slight tangent though, I would assume at least in part that FLC incorporates juvenile blooming? Do polyanthas, tea, china's, hybrid musks and noisettes (maybe?) not demonstrate juvenile blooming (I haven't really dug around in those classes enough to know).
Much of the earlier (19th century) breeding took place in relatively mild climates. Teas and Tea-Noisettes and Bourbon hybrids with Teas and Noisettes, were favored ... along with the older classes that remained popular. But then came 1816, the year without a summer. And then the devastating winter of 1837/38. The tender varieties were not driven to extinction, but their popularity faded just a bit. The hardier derivatives of Gallicas and Damasks crossed with the reblooming types became favored. That some of these were larger than Gallicas, as fragrant as Damasks, and as free-blooming as Bourbons made the emerging Hybrid Perpetual class a winning combination. Exhibition blooms on plants that rebloomed ... more or less.

Later, after much hand-wringing, the HTs became recognized as a class that was neither HP nor Tea. The Shows made these popular even after the Floribundas emerged as (generally) superior garden plants.

Juvenile blooming is independent of the "gene for rebloom".

De Vries: Juvenility in HT Roses (1976)
http://bulbnrose.x10.mx/Roses/breeding/ ... 1976a.html

De Vries, Dubois: Juvenile Period in HT Roses (1977)
http://bulbnrose.x10.mx/Roses/breeding/ ... e1977.html

RBaxter
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Re: Diploid vs Tetraploid - a crossroads

Post: # 68014Post RBaxter
Thu Jun 21, 2018 11:20 pm

I understand the progression to higher ploidy, it's like entropy.

Would a chromosome doubled diploid species still be fertile?

And I don't yet understand the fertility of tetraploids after a few generations. For example Max Graf
R. rugosa × R. wichuraiana, too incompatible for meiosis.
R. kordesii an allotetraploid of the above should be and is fully fertile.
But what happens when R. kordesii is crossed with other roses? I'd bet it was tough at first.

Do fertile tetraploid modern roses carry at least one pair of chromosomes that match up with each other when it's time for meiosis?

Take fertile Hybrid Teas for an example:
Is there perhaps a fully settled set of chromosomes from a combination of R. fedtschenkoana, Rosa moschata, R. gallica, and R. chinensis, that allow at least half of them to pair up orderly? Otherwise, I see complete chaos during meiosis resulting in infertility, And if the fertile moderns do carry that common set on one half, how can we use that knowledge to our advantage?

And if you are big time, how could you use that knowledge to protect your IP?

I love roses, the more I learn, the less I know.
Katy TX Zone 9A

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