That's a great question. I doubt it. Probably Rubus would cross better with Rosa because they are more closely related. In fact protoplast fusion hybrids have been reported with rose and raspberry, also cherry and rose too. Such hybrids look very rose like and if there are any non-rose chromosomes there probably isn't a complete genome. Anyway, more characterization of such hybrids needs to be done. Fragaria (strawberry) and potentilla are close enough and hybrids have been generated. The pink flowered ornamental strawberries are crosses with pink/red potentilla and strawberry and then probably backcrossed to strawberry.

In very wide crosses pollen can sometimes stimulate seed formation and successful endosperm, but often if chromosomes from the divergent male fertilize the egg they may be eliminated. For instance wheat x corn crosses can generate haploid wheat. Oat x corn has generated haploid oat as well as haploid oat plus a chromosome or two of corn that gets through and stabily in the oat genome.

Perhaps your potentilla seedlings are haploid? Perhaps they are apomictic? Perhaps they are mostly potentilla with a chromosome or so of rose that got through? Do they look odd in any way?

Thanks for sharing your experience.

Sincerely,
David

David, thank you for the detailed information of which I really appreciate! I'm very much an amateur so unfortunately, some of it kinda went over my head! I did not notice much of difference with my seedlings though, I kick myself I had not kept them longer for further observation. But, I'm definitely gonna be trying the cross again!

I believe the 'Lipstick' ornamental strawberry came about as a cross between fragaria ananassa X potentilla palustris. This one has been very GOOD for me in my zone 3 garden and always coming though winter even without snow protection! 'Pink Panda' on the other hand is NOT hardy here!

Thanks David!

Terry

There is a published scientific paper titled "The Phylogeny of Rosoideae (Rosaceae) Based On Sequences Of The Transcribed Spacers (ITS) Of Nuclear Ribosomal DNA And The TRNL/F Region Of Chloropast DNA".

Published in: Int. J. Plant Sci., volumn 164, pages 197-211, (2003).

Authors: Torsten Eriksson, Malin S. Hibbs, Anne D. Yoder, Charles F. Delwiche, and Michael J. Donoghue.

Abstract located at: http://www.journals.uchicago.edu/IJPS/journal/issues/v164n2/164022/brief/164022.abstract.html

As you can see from the abstract the Roperculina clade includes Rosa, Sanguisorbeae, and Potentilleae so your crossing does have some support.

In the body of the paper (page 209) it states that Roperculina includes Hulthemia. It also specifically mentions that it includes Rosa cinnamomea, Sanguisorba officinalis, Fragaria vesca, and Potentilla reptans.

The full paper has a number of "trees" that show what is closely related to what. When I first read this paper I put doing some crosses based on it on my "must do" list; but as often happens, I never got around to doing them.
:

Here is a link that might be useful: link for above

Henry, thank you for the additional information. I shall go ahead and again repeat my rose x potentilla crosses ... nothing ventured, nothing gained! With others crossing fruits such as pears x mountain ash, then maybe, I'll try saskatoons x apples in which are in the same family. Half the fun is in the trying! Thanks!

Terry

This old thread (use the next command on the first page of this link to look at the next item in the thread, do the same for the next, etc.)probably is of interest to those that are interested in this thread:

http://www.rosemania.com/_disc3/000002de.htm

Here is a link that might be useful: link for above

Henry, I'm ENJOYING reading and researching as much as possible about rose breeding and such. THANKS for the additional link ... it's appreciated!

Terry

Luther Burbank reported getting sterile hybrids of Rubus and Fragaria, though I've never found much info on these plants. Another scientist I spoke to tried the cross and thought he had something, but in the end concluded that the plants were actually haploid strawberries.

I think it might be theoretically possible to cross Rosa and Potentilla...but it would probably mean thousands of pollinations and a lot of sorting through the accidental open or self-pollinations and parthenocarpic haploid seedlings.

I scanned Burbank's article on the raspberry x strawberry hybrids. It includes a picture. His were definitely not haploid strawberries as they produced underground stolons and smooth canes.
http://www.bulbnrose.com/Heredity/Burbank/Burbank_raspXstraw.html

Karl

Here is a link that might be useful: Raspberry x Strawberry hybrids

Keking - Thanks...Believe it or not, I actually came across that page just two days ago myself. Definitely actual hybrids. Makes me tempted to try it myself, I have to say. The hybrids were probably pentaploids, since they were a cross of octoploid strawberries and (likely, anyway) diploid raspberries. I'd like to take a shot at using diploid strawberries and diploid blackberries (both of which I have on hand here), or maybe octoploid strawberries and tetraploid blackberries, to see if I could get something with even ploidy number and maybe set fertile fruit.

In the Rosaceae, the real forgiving bunch is the Maloideae subfamily...lots of intergeneric crosses have been successful there, particularly with mountain ash (Sorbus). People have crossed apples, pears, quinces, medlars, mountain ash, hawthorns and aronia in all kinds of permutations, although many of these don't fruit or when they do don't produce anything worth eating.

Terry:
Karl has mentioned the Burbank hybreds and in another mail suggested that perhaps Burbank had given up too soon because as hybreds age they can become more stable. Another possibility is that your plants were partial hybreds . Karl could better describe that.
Jerry May

Though I've not seen anything regarding Potentilla, there are numerous cases I know of when diploid strawberries in interspecific or intergeneric crosses, have yielded haploid strawberries. These are generally similar to the mother parent but smaller, and rarely survive to maturity. Since Potentilla are very similar to Fragaria, I wouldn't be surprised to see it behave similarly.

My feeling on letting hybrids age to become more stable is that unless it is something you are deadset on using as a parent, or of some value itself, from a breeders standpoint its probably not worth the space it takes up and the care it will require. Yes, many times 'sterile' hybrids have a change of heart and become at least partially fertile somewhere down the line, but often, perhaps 95% of the time, they just stay sterile, and do no one any earthly good. As a breeder, the single greatest factor controlling success is the number of seedlings that can be cranked through. Every dud you save reduces your chances of finding the truly good seedling by the amount of time, space, and resources it requires.

(That said, if I had an intergeneric hybrid, I'd probably hang onto it a while for the novelty value...I never claimed to be an incredibly efficient breeder).

Elakazal wrote: "I'd like to take a shot at using diploid strawberries and diploid blackberries (both of which I have on hand here), or maybe octoploid strawberries and tetraploid blackberries, to see if I could get something with even ploidy number and maybe set fertile fruit."

The genus Rubus has some "ideas" of its own. In the past, crosses of diploid raspberries with diploid blackberries gave no diploid hybrids at all, only the occasional triploid and tetraploid. I don't know that this would apply when strawberries are involved, but even they can do odd things. I have reports of diploid x octoploid strawberries giving diploid and octoploid seedlings, as well as the expected pentaploids.

I'm guessing here, but I'd prefer to aim for higher ploidy, especially for the pollen parent. Tetraploid x octoploid could give a balanced hexaploid, for example. Diploid x decaploid should also give hexaploids, but with one some of the chromosomes forced to pair against their preferences. That is, a diploid raspberry x decaploid strawberry could inherit four paired sets of strawberry chromosomes; the remaining 7 raspberry and 7 strawberry chromosomes would be forced to pair or be lost.

Karl

Elakazal wrote: "My feeling on letting hybrids age to become more stable is that unless it is something you are deadset on using as a parent, or of some value itself, from a breeders standpoint its probably not worth the space it takes up and the care it will require. Yes, many times 'sterile' hybrids have a change of heart and become at least partially fertile somewhere down the line, but often, perhaps 95% of the time, they just stay sterile, and do no one any earthly good."

You make a good point. But sometimes there are few options. Either we stick within the known fertile crosses, which can get boring after a while, or aim higher.

I just want to emphasize that good things may come to those who wait. Michurin could not have bred his amazing 'Orchid Lily' if he had not waited 8 years for a Lily hybrid to become fertile. I have recently learned that many Peony hybrids start out sterile then become partially fertile as they age.

Early in the last century Arthing Worsley wrote in The Gardeners' Chronicle Feb 11, 1928 (p. 99):
"In a new bigeneric hybrid, maturity in an individual plant is not necessarily the same thing as sexual maturity in the group. We have had many cases in which the earliest hybrids to flower were listed as sterile, but, after years had passed, the hybrid was found to be fertile. This has been the case both with the Brunsdonnas and with Ismene festalis, and also, I understand, with the Zephyranthes x Cooperia hybrids."

Once the initial sterility is overcome, a whole world of new opportunities can be opened to the patient breeder.

Karl

Thanks, Jerry. Yes, partial hybrids are fascinating and probably more common than most people realize. Time and again I've read reports at attempted hybrids that turn out to be "purely maternal"... except. And these exceptional traits are dismissed as "mutations" with no explanation as to why such a mutation just happened to occur following failed cross-pollination.

Sometimes fertilization occurs as expected, but chromosomes of one or the other parent are lost after a few cell divisions. And sometimes the chromosomes behave as though they had been bombarded by X-rays, breaking and fusing. In such cases, some bits of paternal chromosomes are incorporated with the maternal chromosomes, while most of the paternal chromosomes are discarded. (Or the maternal chromosomes may be discarded, though this seems to be rare except in Hordeum).

The result is an almost-maternal plant that does in fact inherit a little paternal heredity.

And sometimes the loss of DNA from the chromosomes does not occur unless the chromosomes are doubled. This has been observed in some grain hybrids, as well as in some brassicas.

Helianthus hybrids (diploids) regularly produce partial hybrids that generally resemble the seed parent overall, but inherit small quantities of paternal DNA.

Worsley's attempts at crossing Isoloma (Kohleria) x Gloxinia (Sinningia) may fall into this category.

Karl

Here is a link that might be useful: Partial hybrid gesneriads

Yeah, I'd definitely think the higher ploidy material would have the best chance of generating fertile Fragaria x Rubus hybrids. Basically, I'd guess more genomes = more chances of chromosomes finding matches to pair up with. Somewhat of an oversimplification, I know, but not a bad assumption, I think in lieu of actual information on what's going on. I've done a fair amount with both Rubus and Fragaria and there are really very few crosses (within the respective genera) that will never work, though getting fertile progeny is another thing. But colchicine can fix a lot of those issues.

Certainly good things have been accomplished by waiting for plants to get over their initial sterility. But in general a lot more has been accomplished through standard fertile crosses. While every breeder has a different approach, I still think a more productive course, especially for hobby breeders with limited space and time (not that the professionals aren't limited on those counts, too) is to keep unproductive material for as little time as possible. Every non-useful seedling takes up resources that could be dedicated to a new seedling of untested potential. Obviously each case has to be weighed on it's own merits, of course.

That's just me, though. I've known a lot of breeders, and some are of the "well, let's keep it around for another season" school, and some are more of the fast-moving production line approach. There are good breeders of both schools, and both have their pros and cons, but my preferences generally lean towards the later.

Elakazal,

Have any of your plant breeding friends found sterile hybrids that became fertile with age? I'd like to get more information on the subject -- and more cases. I'm hoping that we may find details that will allow us to predict which are likely to recover.

Not all will, of course. There's a sterile cycad colony in New Zealand that is thought to be around 40,000 years old. That's a bit too long to wait.

There is also theoretical interest in this subject. If a sterile hybrid can become fertile in 5 or 10 or 30 years, why was it sterile in the first place? What changed to allow fertility?

Also, it is well to note whether the whole plant becomes fertile, or just the occasional flower.

The more we learn, but better the chances that we will find a way to overcome some kinds of sterility. At any rate, ideas about "bad genes" or mismatched chromosomes just won't fly, because the fertile old specimens generally have the same chromosomes and genes they had when they were young and sterile.

It's worth noting that the rose 'Paul's Scarlet Climber' is a triploid, and is sterile when grown on its own roots. But when grafted to a suitable rootstock it becomes fertile.

The same is sometimes true of species grown outside their native environment. J. H. Nicolas reported that Rosa hugonis was sterile in his garden on its own roots, but fertile when grafted -- same as 'Paul's Scarlet'. Other varieties were sterile in some soils, fertile in others. Obviously the genes and chromosomes have not changed in these cases.

Karl

Here is a link that might be useful: Anomalous Heredity

I will enquire with folks as to particular cases of sterile hybrids becoming fertile. I've had a few related to me in Rubus, but I don't really recall the particulars.

A much more common, but not necessarily analogous, situation is the plant which doesn't flower for years and years, and then suddenly begins doing so. In such cases it may be an extended juvenile period or a plant which was just not happy. There are also instances of sex changes. In grapes we had a male vine (some wild American species, I don't remember which) which set a whole cluster of small fruits one year (I planted the seeds but only two seedlings came up and neither lived long). I've also seen this in male hardy kiwi vines.

In many cases perhaps the sudden appearance of fertility might be some sort of sporting. Certainly a spontaneous doubling of chromosomes would alleviate problems with pairing and odd ploidy numbers. But this wouldn't explain all cases.

Other idle musings on the topic: Some may involve the relatively poorly-understood effects of gene-silencing, too, particularly in polyploids. For example, since excessive expression of a gene can result in the degradation of all such transcripts or transcripts from one parent or the other, a polyploid might easily wind up silencing genes important for reproduction. There appears to be a certain threshold level to trigger silencing, so it's possible that if levels of expression fall below that level, gene silencing would cease and the remaining low levels of the transcript would be enough to allow normal reproduction. Gene-silencing effects (at least artificially induced ones) have also been shown to cross between scion and rootstock as well, which might explain the 'Paul's Scarlet Climber' issue. Anything which effects gene expression (which is everything) could conceivably effect silencing.

I also think that certain species may be more inclined towards sexual reproduction when stressed. Certainly if your genotype makes you do well in a given environment you'd be better off multiplying vegetatively than rolling the dice with recombination...but if you're poorly suited to your situation, a reshuffling of the genes might work out better. I don't know of any cases where this happens in the form of lost or regained fertility, but it makes some sense from an evolutionary point of view.

Anyway, just thoughts. (It's 3 am, so they may not make quite as much sense to me tomorrow when I'm awake, but anyway...)

By the way, I really enjoy your website, Karl.

Elakazal,

It is not immediately obvious why gene silencing would be involved in making a "sterile" triploid fertile. Whatever the precise effect, it is apparent that triploidy alone is not sufficient to explain the sterility.

It might be that something else is being transmitted in the sap that alters the crossover frequency -- reducing it enough to limit the number of trivalents formed. Pollen and ova could then receive 7 or 14 chromosomes (or nearly) rather than 10 or 11 that might be expected if trivalent formation were more common.

An increase in temperature may have a similar effect. See Wulff's article on fertile triploid roses linked below.

Sex change in Kiwi fruit vines reportedly involves changes in gene activation, specifically a loss of methylation. Loss of methylation can be induced by ethionine and 5-azacytidine. To increase methylation one may use vitamin B12, folic acid, choline or betaine.

It would be an interesting and inexpensive experiment to combine methylating or demethylating substances with caffeine, which can induce somatic meiosis. Such a treatment might produce an assortment of "mutations" without the chromsome damage associated with X-rays or Cobalt-60 exposure.

Glad you like my web page. I like posting the sort of articles that I would have enjoyed reading when I was a teenager just getting started. Textbook Mendelism is just too boring and pointless.

Karl

Here is a link that might be useful: Cytology of Two Fertile Triploid Roses

Good point. I actually wasn't thinking triploidy in particular when I was discussing the gene silencing angle...I apparently just glossed over that fact about "Paul's Scarlet Climber" when I was reading. (In my defense, it was 3am). The cases I was thinking of were more those where "sterile" offspring such as those which might result from a wide cross but are of even ploidy. Gene silencing would probably be more of an issue in higher ploidy levels, anyhow.

I will confess to a relative ignorance of roses (moving into my new house in November I now own my first three, though, and may make a cross between them this season, just for kicks), and my knowledge of cytogenetics is a little spotty. After reading about meiosis in dog roses, though, I'm prepared to believe all kinds of goofy things go on in their reproduction.

I guess one big question is how fertile is "fertile"? Theoretically, even given relatively standard models, triploids ought to create normal gametes once in a while (though the odds are very small). How much of a deviation from this is required before something is called fertile? If a species produces zillions of ova and tons of pollen, relatively low rates of normal gametes can pass for semi-adequate fertility (I don't know that such a species exists, I'm just saying its a theoretical possibility). In something like, say, peaches, the same relatively low rates might appear as complete sterility.

The other question, which I see is mentioned in the link you attached, is whether apomixis counts as fertility. Is it possible 'Paul's Scarlet Climber' is apomictic? Inducing apomixis would certainly be a lot easier to explain than inducing regular meiosis in a triploid. Are its progeny diploid, triploid, or tetraploid (or any other ploid)?

I'm interested in your suggested experiment. I've had the caffeine idea on the back burner of my brain for a while, looking for some interesting way of implementing it. (My mother, who waters her plant at work with her excess coffee, wondered if she should be on the lookout for odd growth when I told her about it...) Any suggestions on concentrations? I may dig around a little.

Textbook Mendelism is hardly pointless, just a gross over-simplification. I think it would be a little silly to think that something as incredibly complex as a higher organism would be governed, without exception, by such simple rules.

The articles you've posted are the sort of things that often escape notice these days. Molecular breeding has resulted in a lot of breeders who barely notice anything published pre-1990, and many of the more traditional breeders remaining stick to pretty established routines. Strange results get dismissed as errors or declared not worth investigating. I was thrilled to find something of a repository of these sorts of accounts. It is not easy to come across such papers without doing a bit of digging, if you don't have some one to point you to them or a familiarity with the older literature. It's not impossible to find them, but it generally requires a trip back through several generation of references before you can find them.

Anyhow, thanks.

Elakazal,

One time several of us on a rose group assembled a list of 'Paul's Scarlet' progeny. Most of them are reblooming Floribundas, and all are distinctly different from PS. Some, at least, are tetraploid.

Fertility of triploids is at least partly related to crossover frequency. In some cases of rose triploids most gametes have 10 or 11 chromosomes, which doesn't work well. Remember, egg sacs and pollen tubes are multicellular organisms that rely on the "genes" contained in the chromosomes to function. Weird chromosome numbers can harm them.

In other cases rose triploids give chromosome numbers approximating a multiple of 7, then discard the one or two extras.

===
I am not keen on Mendelism because it tells us nothing useful about what happens in wide crosses -- until after the fact. And then only to "explain". It lacks predictive power. There are instances of crosses within species, between geographical "races" that do not differ appreciably, that give considerable variation among the offspring.

I won't run on about that just now -- it's 4:30AM.

Besides, I'm continually annoyed by the dogma that Mendel discovered something by analyzing his data. This is nonsense. He was not a statistician. If he understood probability at all he would have raised more than 10 seedlings when he was trying to determine whether a plant was heterozygous for a recessive trait. This means that while his numbers look good, they actually contradict his assumption. He was getting too many heterozygotes and misidentifying some of them as homozygous dominants. Or he was very, very, very lucky.

In the real world one must raise 24 seedlings in order to identify 999 heterozygotes out of 1000.

===
Fertile is as fertile does. You're quite right about the relativity involved. A rose hip might contain 100 seeds. But if a hybrid produces only 1-3 seeds per hip we call it weakly fertile or nearly sterile even though it is doing at least as well as a peach with its one seed per flower. 'Penelope' and 'Paul's Lemon Pillar' are a couple of fertile triploids that produce only one or a few seeds per hip. But the hips of 'Penelope' are a beatiful coral pink while those of 'PLP" are very large and yellow -- so conspicuous that we tend to think of the plants as fertile even before we start counting seeds.

I got hooked on old journals back in my college days. They were there so I started reading them. Often there is a cummulative index covering a year or a decade, which helps a lot. But time and again I've looked up a specific article only to find something even more interesting in the same issue. The thrill of discovery offsets the drudgery and old book dust. When I visit a library I take a pocket full of change to make copies. Often I have something in mind, then find references in the articles that lead me off in a different direction. Then I walk out with half a ream of copied articles.

It is important to look to the old stuff for what has been overlooked. Just last year, or the year before, someone discovered a "new" mechanism to insure crossing within a species. A ginger was found to have two morphs, each with perfect flowers. One morph released its pollen in the morning while keeping its style curved upwards and out of the way. In the afternoon the style bends downwards and the stigma became receptive. The other morph reverses the sequence, functioning as female in the morning, male in the afternoon. Pretty exciting stuff! Soon it was found that the same mechanism had been reported for an unrelated plant (filbert?) in the late 19th century, but no one paid attention to the discovery. These details have to be observed in living plants, by the way, because the differences wouldn't be noticed in herbarium specimens.

And in the early 19th century a French hybridist was counting the male and female plants that came from gourd seeds, and noted that males and females had fairly definite locations within the fruit. Correns rediscovered the phenomenon in Lychnis (Melandrium) in the early 20th century, and DeVries discussed something similar in regards to double-flowered Stocks.

By the way, DeVries and Correns were not as excited about Mendelism as one might assume, and Tschermak was only interested in the segregation -- not the magic numbers. In fact, Tschermak visited DeVries while both were conducting their experiments but neither brought up the subject. DeVries was far more interested in his studies of "mutations" and eversporting varieties. Correns then began studying "segregation distortion" while academics around the world were finding ways to doctor their data to get "good numbers".

It's this magic number business that I regard as pointless. And the independent segregation doesn't always work out due to linkage -- something Mendel could not conceive. Thus, the ratios of segregation cannot be calculated in advance. When you get right down to it, there isn't much originality in Mendel's work after you sort out what he got from Naudin. And what was genuinely original is not very helpful to a practical breeder.

Karl