R. moyesii 'Highdownensis'

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Karl K
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Re: R. moyesii 'Highdownensis'

Post: # 65320Post Karl K
Sat Apr 08, 2017 11:35 am

Another thing to consider is whether we may reasonably assume that two diploid species could give rise to a new tetraploid species under natural conditions. Natural hybrids are known in Rosa, of course, but these seem to be rare and short-lived. At least, we do not see new tetraploid species spring up wherever the ranges of two diploid species overlap.

But something different may occur during times of changing climate. It is known, for example, that a mature specimen of a species may survive in a region where its seedlings have little or no chance of surviving to maturity. And when the climate is changing, a lone specimen may hang on as another species moves into the region.

I recently found a paper by Nakamura et al. [Molecular based evidence for a lack of gene-flow between Rosa x hybrida and wild Rosa species in Japan, Plant Biotechnology 28, 245–250 (2011)].
In the present study we analyzed the seedlings of seeds from three wild native Rosa species (R. multiflora Thunb., R. luciae Rochebr. et Franch. ex Crép. and R. rugosa Thunb.) selected from several locations across Japan where the wild rose was growing in close proximity to cultivated rose plants (Rosa x hybrida). To determine whether gene flow from cultivated rose had occurred, young leaves of 1,296 seedlings from the wild Rosa plants were analyzed by PCR for the presence of the KSN locus. This locus originated from a sport of R. chinensis Jacq. var. spontanea (Rehd. et Wils.) Yu et Ku and is involved in the recurrent flowering phenotype observed for cultivated rose hybrids, but is absent in Japanese species roses. The KSN locus was absent in all seedlings sampled, indicating no gene flow to wild Rosa species from the cultivated rose had occurred, and providing evidence that the probability of gene flow from cultivated to wild Rosa species in Japan is low or non-existent.
https://www.jstage.jst.go.jp/article/pl ... 1217a/_pdf

That seems definite enough, but I was reminded of something else.
The Garden p. 136 (Feb. 16, 1878)
Rosa polyantha.—Mr. George Paul having told us of the beauty of this Rose as a vigorous climber in Mr. J. Sisley's garden at Lyons, we, in reply to an inquiry, received the following note from that veteran amateur, who has enriched our gardens with so many good varieties of plants:—
"As to the principal object of your letter, I can say but very little. I have possessed Rosa polyantha since it has been introduced from Japan. It is a very hardy shrub, having stood with me the severe winter of 1870, when we had, in December, 24° Centigrade below freezing point. The flowers are white, small, and single, but they are borne in clusters, like the Lilac. It seeds freely. It needs no pruning; quite the contrary. I have obtained from its seeds several varieties with double flowers, which are about the form and size of those of R. multiflora; they are generally white, but some are tainted yellowish or pink. I must suppose that the mother plant has been fertilised, through insect agency, with the pollen of other Roses, because my son, who is an engineer in Japan, wrote to me that in the neighbourhood where he resides, where the Rosa polyantha grows wild on the hills, it always comes true from seed, but that may happen because there are no other Roses in the neighbourhood."
https://books.google.com/books?id=m9M7A ... &q&f=false

Clearly, the Japanese form of R. multiflora sometimes received pollen from garden roses when a lone specimen was growing in a French garden, but it is much more likely to be pollinated by other specimens of its own species while growing in the wilds of its native Japan.

The same is likely to have occurred during ancient times of climate change, whether of warming or cooling. An old specimen clinging to life could receive or share pollen with an invading species. The hybrid could exceed either parent — perhaps gaining tolerance of local soil conditions from the old one, and tolerance of the new climate from the other. Occasional tetraploid offspring from the diploid hybrid could then continue on where neither of its parents were fully adapted.

Hurst (1932) touched on this subject:
Mechanism of Creative Evolution (1932) pp. 112-113
C. C. Hurst
Several external factors may be the cause or occasion of this duplication of chromosomes. A severe frost, for example, will temporarily suspend divisions in the pollen grains and cause some germ-cells to form (provided the frost has not been too severe), bearing twice the normal number. These on fertilising normal egg-cells will produce triploids or, if the egg-cells have been similarly affected, tetraploids. In gardens where many plants are out of their natural environment, having come from countries with more regular climates, such occurrences are not infrequent. In their own country, once the winter is over, they produce their flowers with no set-backs, but in England, where we get a warm spell in the spring long enough to bring out the flowers, often followed by a severe frost for several nights just as the flowers are forming, many aberrations and abnormalities arise. Similarly in a wild state, an unusual season may upset many of the normal mechanisms of the plant. De Mol has discovered that many of the different chromosome types in bulbous plants have been due to the custom of drying off the bulbs after the flowering season and, in the case of bulbs for commerce, the subsequent forcing to produce early-flowering for culture in pots. These bulbs, being subjected to various degrees of temperature at the time of the formation of their germ-cells (these being formed deep down in the bud during the previous summer or autumn before flowering), produce various irregularities of division. Many of these irregularities fail to carry on but the few that struggle through will give rise to new races, sometimes of great beauty, for our gardens.

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Re: R. moyesii 'Highdownensis'

Post: # 65323Post Don
Sat Apr 08, 2017 2:28 pm

No matter how you spin it Hurst's theory is archaic. It's a distraction that hangs around because it is accessible to the layman both physically and intellectually. It is of no use at all to the rose hybridizer.

Unfortunately there is no modern treatise accessible to the lay hybridizer to replace it.
What doesn't kill them makes them stronger.

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Re: R. moyesii 'Highdownensis'

Post: # 65326Post dgermeys
Sat Apr 08, 2017 6:24 pm

Karl, thanks for the extra information!

Don, one might call the septets a distraction, but would you say that is entirely wrong? Rosa Rugosa (diploid) is clearly totally different than rosa Arvensis (also diploid), and I believe, when one would compare the chromosones in offsprings of them, what would we see during the meiosis? Will the offspring be able to form pollen or eggs? I doubt it... So how would you explain this?

Dane from Belgium

Karl K
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Re: R. moyesii 'Highdownensis'

Post: # 65328Post Karl K
Sat Apr 08, 2017 10:04 pm

There are chromosomal differences even between species that are rather closely allied. Hurst (1941) discussed such a case:
PARSONS' Pink China is still in cultivation in country gardens and there is an excellent figure of it in REDOUTÉ (1817) under the name of R. indica vulgaris. Analyses of its characters show the influence of the Wild Crimson China (R. chinensis) in 16 of these, while the remaining 12 characters show the influence of another species, the Wild Tea Rose (R. gigantea). PARSONS' Pink China may therefore be regarded as a hybrid between chinensis and gigantea. It is not, of course, an ordinary primary hybrid produced directly* between the two species but rather a derivative hybrid derived after generations of crossings in Chinese gardens. Parsons' Pink China is a diploid with 14 chromosomes in the body-cells and 7 in both the male and female germ-cells. Although a diploid, its chromosomes are not regular in their behaviour and weak pairings in the germ-cell divisions lead to defective pollen and embryo-sacs and consequent sterility. In this respect the Pink Chinas behave as hybrids rather than pure species. Among the newer varieties of the Pink China I have found several triploid forms with 21 chromosomes which have no doubt arisen by duplication of the chromosomes in a pollen or egg-cell, as in the case of the triploid Crimson Chinas.

* Genetical confirmation of this is found in the appearance of true-breeding gigantea characters in the original crosses of Noisette and Bourbon with the Blush and Yellow Chinas, giving rise to the race of Tea Roses (R. gigantea Collett).
While researching early breeding of the Teas and Chinas, I was surprised to learn 'Hume's Blush' and 'Knight's Yellow' were the preferred breeders in England because 'Parsons' Pink' rarely set seed there. In France, however, 'Parsons' Pink' was more successful. The imperfect pairing of the chromosomes may account for the Minis and Semi-Minis that have been raised from self-seeds of 'Parsons' Pink'.

Chromosome differences can be found even in a single species, which sometimes indicates hybridization.
The Southwestern Naturalist, Vol. 3, No. 1/4 (1958), pp. 151-152
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).
I think that it is more important to appreciate the relevance of linkage groups to breeding, especially when at least one of the linked traits can be observed in young plants.

Austin (1993) found when breeding from 'Conrad Ferdinand Meyer', Rugosa-ness behaved as a unit character.
"Some of the seedlings from this cross were of typical rugosa appearance, while others bore absolutely no resemblance to a Rugosa Rose. It seemed that some of our hybrids had taken the genes only from the 'Gloire de Dijon' half of 'Conrad Ferdinand Meyer,' while others had inherited those from the Rugosa side. What we had in many instances were in effect hybrids of 'Gloire de Dijon.'
Whether you are looking for Hybrid Rugosa type roses or non-Rugosa types, 'Conrad Ferdinand Meyer' can provide them. And the differences will be visible as soon as a few true leaves have formed.
Iowa State Journal of Science: 35: 255-260 (1960)
Some notes on the use of Rosa laxa as a source of hardiness in rose breeding
Griffith Buck
"Pollen from the 'Crimson Glory'-R. laxa seedling was effective in producing viable seed on a wide range of cultivars of the Hybrid Tea, Floribunda, and Grandiflora garden classes. The seedlings segregate into two sharply defined groups of approximately equal numbers. One group bears a pronounced resemblance to R. laxa in growth habit, foliage and prickle characteristics. The flowers, which are borne only in June, are single, two to three inches in diameter, and are in the lighter tones of pink, salmon, and yellow. All the plants in this group are as hardy as the species parent. The plants of the second group resemble the garden rose parent in floral and foliage characteristics. The plants are June-blooming; the everblooming habit of the Hybrid Tea and the remontance of R. laxa being absent. All plants of this group winter-killed during the winter of 1958-59, even though they had been given winter protection. All the seedlings retained the freedom from powdery mildew and the susceptibility to blackspot of the 'Crimson Glory'-R. laxa parent."
http://bulbnrose.x10.mx/Roses/breeding/ ... a1960.html
In this case, if you need extra hardy plants, you could cull those seedlings that do not look Laxa-ish.

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Re: R. moyesii 'Highdownensis'

Post: # 65332Post dgermeys
Sun Apr 09, 2017 5:17 pm

Hey Karl,
Karl K wrote: Parsons' Pink China is a diploid with 14 chromosomes in the body-cells and 7 in both the male and female germ-cells. Although a diploid, its chromosomes are not regular in their behaviour and weak pairings in the germ-cell divisions lead to defective pollen and embryo-sacs and consequent sterility. In this respect the Pink Chinas behave as hybrids rather than pure species.
This confirms my thinking. Hybrids from different species, with different septets so to say, will result in roses that have trouble forming offspring, because, I believe, somehow the chromosomes will not be attracted to the poles or something like that. I don't know what exactly will be the problem but it seems to me that only when two 'similar' chromosomes (x 7) find each other, they will be able to duplicate and start the meiosis.

But I'll see if I can buy a good book on plant genetics later this year. (For reading during winter time ;-) )

For now, I bought Rosa Moyesii 'Highdownensis' and I'll try to breed with it. I hope it will give me the pollen I want to use. I might also try to cross it (as a seed plant) with a rugosa. Problem here is that I don't have any rugosa species, only hybrids. Well, we'll see what will come out of it :-)

Dane from Belgium

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Re: R. moyesii 'Highdownensis'

Post: # 65336Post dgermeys
Mon Apr 10, 2017 2:43 am

But then again, how is it possible that a cell can perform the mitosis but not a meiosis?
Dane from Belgium

Karl K
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Joined: Sat Jun 02, 2012 4:49 pm

Re: R. moyesii 'Highdownensis'

Post: # 65339Post Karl K
Tue Apr 11, 2017 11:48 am

I found a short animated video that shows the difference between meiosis and mitosis in non-hybrid cells.
https://highered.mheducation.com/sites/ ... tosis.html

In hybrids where the chromosomes do not match up properly, mitosis still proceeds with little difficulty because the chromosomes do not pair. Each chromosome is replicated, and the two copies are dragged to opposite sides of the cell before it divides.

In some hybrids the chromosomes do not pair up normally, sometimes due to various rearrangements in the chromosomes (segmental interchange, translocations, inversions, etc. In such cases the "pairing" may involve parts of three or more chromosomes. Erlanson (1931) found that 'Orleans Rose' has a segment that is located on two non-homologous chromosomes. Call the segment "+". It is present on one copy of chromosome A (A+) and one copy of B (+B). During meiosis, A may pair with A+, which then pairs partially with +B, and the latter can still pair with B. That's A A+ +B B, all tangled together by the cross-overs. This group takes longer to untangle than normal pairs, which can result in gametes with extra or missing chromosome. In addition, some gametes may have the right number of chromosomes, but with 2 or 0 copies of the segment +. I.e., A+ +B or A B. Whether these are even viable depends on what genes are in +.
http://bulbnrose.x10.mx/Roses/breeding/ ... me1931.pdf

An inversion occurs when a segment of a chromosome become reversed in its orientation. This is not a problem in mitosis, but can be troublesome at meiosis. If one chromosome carries a large inversion but its partner does not, the two chromosomes may start to pair within the inverted region, then "try" to match up one or the other end. Again, the tangling can take longer to pull apart, resulting in a gamete with two copies of the chromosome, or none. And again, whether a resulting aneuploid (with a chromosome too many or too few) can survive depends on which genes are located on it.

There are too many other possible complexities to list here, but they are all potentially relevant to evolution and plant breeding.

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