Ploid Cross Matix Tool?

I read this ploid focused abstract with interest, and as a layperson. I conclude for my purposes one can cross pretty much any ploids in a plan up to tetra with a margin of success. Without saying anything of the garden merit of the seedlings.

Or does anyone know of a published reference - rather than relying on memory - giving say a simple 4x4 M/F (or 3x3? sans haploid), or larger indicator matrix of ploid combos versus “efficiency / fertility of seed set”, and germination ? Seems like one could construct one from just this abstract as a general guide.

Or assuming the roses in a pair are fertile, why worry, its not practical or predictive, just do the cross and find out (always my default approach).

Abstract from:

“Interspecific crosses between diploid rose species and tetraploid cultivars yield triploids …”


"Using such triploids as pollen parents and tetraploid plants as seed parents resulted in relatively high seed set. Although efficiency was lower, reciprocal crosses with the triploid plant as a seed parent also yielded some seedlings.

Screening of the progeny showed that seedlings obtained after a cross between a tetraploid seed parent and a triploid pollen donor are mostly tetraploid.

In the reciprocal cross, both triploids and tetraploid seedlings are found. These results indicate that triploid rose plants form both haploid and diploid pollen and egg cells.

However, in pollen production, the diploid fraction seems to have a competitive advantage over the haploid. Molecular marker (AFLP) data show that markers can be passed on from the diploid species to a tetraploid F2 generation via a triploid F1."


Interploidy crosses in roses: Use of triploids
September 2005Acta Horticulturae 690(690):109-112

DOI: 10.17660/ActaHortic.2005.690.15

Johan Van Huylenbroeck Institute for Agricultural and Fisheries Research
Leen Leus Institute for Agricultural and Fisheries Research
Erik Van Bockstaele Institute for Agricultural and Fisheries Research

I don’t know about anyone else, but I usually only make crosses under one chromosome number-driven restriction, generally only using the diploid as seed parent when crossing with a tetraploid, just because the chances of reasonable seed production tend to be much higher. Other than that rather specific scenario, ploidy is a fairly minor consideration for me. The fertility of each variety, and the cross-compatibility of each pairing, tend to be far more important, and both are generally not a direct consequence of ploidy.



Txs for the feedback. I am slowly coming to the conclusion that the knowing ploid question is not a rigid straight jacket conformity rule in hybridizing. This is useful as in my searches it seems a challenge to find the ploid data for a good chunk of my rose inventory, and also not yet recognizing the critical need to know it except perhaps seed set output. Or passing through a pursuit line in crossing history.

It still more important at this stage that l recognize those roses that are fertile as either/or parents … that seems to come from garden op observations, trial crosses and experience sharing of trial crosses.

For roses there is no bottom line answer to the question of whether ploidy is the cause of a failed cross because there are other possible reasons for failure. Chief among these is the problem of self-sterility. Moreover, it is pretty much impossible to ensure that any given successful cross is free of selflings.

This is true for the professional rose hybridizers, not just amateurs. Whereas professional apple, cherry, cucumber, lettuce or corn breeders, say, have worked out the complexities of self-sterility, ploidy effects and, to some degree, epigenetic effects they work with a more narrow genetic base than we do and mostly with diploid breeders. Where they do need to consider polyploidy they are in pretty much the same boat as we are.

The best you can do is make the cross, hope for the best and, if you get seeds and they germinate, look for evidence of hybridity. Long-shot crosses do sometimes succeed.

Here is an interesting discussion of a long-shot cross that will give you some idea of what happens when you do manage to mix disparate genomes. In this case it is diploid x diploid so imagine the how much more crazy it gets with interploid crosses.

Thanks Don

Interesting and informative. Believe it buffers a tendency l have to lean towards rote crossing behaviour, but doesn’t discount basic “ploid” knowledge as a good guide for part of a plan to increase true crossed seed take - plan goal(s) have not changed, e.g. bone hardy fragrant vivid coloured climber (Fn?) or rambler (F1?).

However the wild card ploid cross approach continues to appeal (aka tetra and ambloid (sic)) due to the roll the dice technical rite rules ignoring component … appealing … but the recognition skill level maybe missing at this time, as well as calendar time.

Thanks again for motivation push.

Years ago I bought a copy of The Chromosome Atlas by Darlington and Dr. Janaki-Jamal. It is an interesting collection of chromosome count data from a wide range of plants. But when I checked chromosome numbers of plants that Luther Burbank had used in his work, I learned that if he had restricted his crosses to easy crosses (same chromosome numbers) then we might not have Shasta Daisies, White Blackberries, Stoneless Plums and many other useful plants.

In roses, some triploids are quite fertile, some moderately so, and others as close to sterile as plants can be. Rowley (1960) lists an assortment of triploids with their relative fertility. Wulff (1959) shows that temperature can influence fertility. Erlanson (1931) gives an advanced discussion of chromosome crossovers and other hindrances to fertility.

Rowley: Triploid Garden Roses (1960)

Wright: Triploids in Rose breeding (1969)

Wulff: Triploid Cytology (1959)

Erlanson: Chromosome Organization in Rosa (1931)

Txs Karl

Lots info packed in to read and digest … see one tabulation that would be useful as a template to modify for creating a inventory semi quantitative record of observations and public domain ploidy data.

Walter Lewis Rosa foliolosa: free download. Ebooks library. On-line books store on Z-Library
The Southwestern Naturalist, Vol. 3, No. 1/4 (1958), pp. 145-153
A Monograph of the Genus Rosa in North America. II. > R. foliolosa
Walter H. Lewis

Although the mitotic leaf chromosomes from only one plant were studied in detail, several plates from this specimen showed the following karyotype (Figure 3):
1 pair long median chromosomes (aa)
1 pair long subterminal chromosomes (cc)
2 pairs medium median chromosomes (dd, dd)
1 pair medium submedian chromosomes (ee)
1 pair medium subterminal chromosomes (ff)
1 pair short median chromosomes (gg).

This morphology is similar to that for > one form > of > R. Woodsii > Lindl. except that—as observed here—one pair of long chromosomes has a median centromere in > R. foliolosa > and the corresponding pair in > R. Woodsii > has a submedian centromere. The chromosome morphology of > R. foliolosa > is also similar to a second diploid species, > R. palustris > Marsh. The latter has a long submedian pair (bb) and two pairs of medium subterminal chromosomes (ee, ee), while > R. foliolosa > has a long median pair (aa) and only one pair of medium subterminal chromosomes (ee).

As Lewis noted, the list of chromosome forms were observed in a single specimen of Rosa foliolosa. Much more research would be needed to determine whether the same types of chromosomes will be observed over the whole range of the species. Also, he noted that the morphology was similar to what had been observed in one form or R. Woodsii. Not in all.

Variations in chromosome structure are not uncommon within species, and are even more common between species. These differences put distinct limits on the types of reassortment that may be observed in the progeny of hybrids. If we look only at a few traits, we might imagine that Mendel got it all right. But where more traits are considered, some discrepancies appear.

If the form of Woodsii mentioned above were crossed with the Foliolosa Lewis examined, we should expect some non-Mendelian patterns. The difference between a long chromosome with a median centromere (Foliolosa) and one with a submedian centromere (Woodsii) suggests that there has been some rearrangement of DNA in the chromosomes.

Maybe the extra bit on the Foliolosa was borrowed from another chromosome. This works out in the species because each offspring (within the species) gets two copies of that bit. But in the hypothetical Woodsii x Foliolosa hybrids, some might get an extra copy or two, while others come up short by one or two. Depending what sort of genes are in that bit, these changes may be lethal, or produce some puzzling “mutations” to keep us guessing.

Rowley (1960) wrote “The progeny of triploid roses only very rarely include triploids…” There are exceptions.

For example, the original Bourbon was almost certainly a triploid. And triploidy persisted down to 'Souv. de la Malmaison. If the crossings led to a Tea-like plant, it would have been listed as a Tea. A tetraploid seedling would probably lack the delicacy of the Tea/China ancestry and end up more like a Hybrid Perpetual.

We see a similar pattern with the early HTs. ‘Lady Mary Fitzwilliam’ (3x) was reportedly bred from Devoniensis (2) x Victor Verdier. Considering that Victor Verdier is reported as Jules Margottin x Safrano, it may be a triploid.

And Mme Caroline Testout (3x) is Mme. de Tartas (2x) x Lady Mary Fitzwilliam (3x).

There may have been Tea-like siblings that were discarded, or even some that were closer to modern HTs than was then fashionable.