Royal Court Jester
This is Royal Court Jester. He is not an Arabian horse (no panic yet). He carries less than 0.2 percent pinto blood from a single cross at the 10th generation. The remaining 99.8 is general list Arab blood.
Tobiano is a dominant gene, so at least one parent need to carry it. I wonder, through, whether this is the same gene as that responsible for extra white markings? My question reflects my ignorance of equine genetics.
This question is more complicated than it looks, because “gene” in this kind of discussion can refer to either of two things: the tobiano _mutation_, or the original gene location at which that mutation occurred. The tobiano mutation can be recognized at the DNA level as well as phenotypically, and it is not seen in Arabians.
There are a number of genes (genetic locations or loci, singular locus) which influence the development of white markings, and I know of no research into how to recognize the DNA-level cause of the kinds of Arabian phenotypes Edouard has been posting. It is possible that some of them result from other changes at the same genetic location as tobiano, but then again there’s no evidence for that, either.
Here is a quick summary of the association of white markings with domestication;
https://www.sciencedaily.com/releases/2014/07/140714100122.htm
if the Arabian is at least one of the oldest domesticated horse populations it is not surprising to read of extensive white markings in the old Arabic literature, or to see them coming out again in modern horses where, as Jeanne points out, the anti-markings selection has come to be less uniformly applied. By this reading they are the reverse of indicating crossbreeding. Their visual difference from tobiano and other spotting patterns supports that–these are coming to be distinctively Arabian phenotypes.
The short answer is no, tobiano is not the same gene as the one(s) controlling white markings in Arab horses.
The slightly longer answer is that a number of white spotting patterns are be associated with mutations in the KIT gene, including tobiano and (some of) the white spotting found in Arabians. Tobiano, as a pattern, has white which crosses the topline, and typically has smoother edges to the white markings. There is a particular mutation within the KIT gene, plus a chromosomal inversion, that are found in tobiano horses; the gene is named T.
White spotting in Arabians is a different beast from tobiano. So far, the white markings identified in Arabians have all been associated with what was once called dominant white. Where tobiano is dominant, and thus requires just one copy of the gene to produce the pattern, the various W genes appear to be incompletely dominant, so that a heterozygous Ww horse has less white than a homozygous WW horse. (Some versions of W are homozygous lethal, though, but not all.)
The W genes are also mutations in KIT, and last I checked there were something like 27 identified W patterns, named W1 through to W27. Quite a few of them are novel mutations – KIT seems prone to spontaneous mutations – so in Arabians, white spotting patterns that originated in the twentieth century with a single horse are W3 (R Khasper), W15 (Khartoon Khlassic), W19 (Fantasia Vu), and W23 (Boomori Simply Stunning). These specific white spotting patterns were not present in the population before, and are only found in the descendants of these horses.
W20, on the other hand, is an older KIT mutation, which is found in multiple breeds, including the Arabian. It is interesting, because it seems to be able to combine with other KIT mutations and boost the amount of white they display. W20 produces patterns once called sabino (now sabino-like because of genetics and naming conventions), i.e. big blazes, white stockings with sharp points, belly spots, jagged edges to white. My guess is that W20, or a KIT mutation very like it, is behind the white in Mesaoud, Rodania, and other Arabians with sabino-like markings. A horse like Marbon Masterpiece or Fenwick Orion could be homozygous for W20, or might have W20 present as a white booster in combination with another KIT mutation. Without running a test for white spotting, there is no way of knowing.
But! Tobiano is different from white spotting in Arabians, and if a horse has tobiano, then it is not an Arabian horse. The gene is not present in the population.
There’s a horse that I recently came across who had similar markings.
Fantasy Fashion
https://www.allbreedpedigree.com/fantasy+fashion
Right side: https://public.fotki.com/hypoint/arabians/arabian_album_sabin/fantasyfashion.html
Left side: https://public.fotki.com/hypoint/arabians/arabian_album_sabin/fantasyfashion75786.html#media
No known tobiano that I’m aware of, just a lot of ancestors with various forms of white spotting.
Kate, just addending that W28 was recently identified in German Riding Ponies, A new KIT mutation, designated W28, has been identified in a German Riding Pony! Tosso Leeb’s group from Uni Bern and colleagues identified “a heterozygous 1273-bp deletion spanning parts of intron 2 and exon 3 of the equine KITgene (Chr3: 79 579 925–79 581 197).”
The mutation is de novo with the foal, Phantasio, by Coelenhage’s Purple Rain (a bay stallion with four small socks and a stripe) and out of Rolexis (a red mare with one sock and a stripe.)
You can see photos of him here: https://m.facebook.com/story.php?story_fbid=491858774710722&id=100016598101731
Interestingly enough, the GRP gene pool has a high % of Arabian influence. Would be interesting if there was a correlation.
Kate- What study are you getting this information from?
W3 (R Khasper)
W15 (Khartoon Khlassic)
W19 (Fantasia Vu)
W23 (Boomori Simply Stunning)
These horses are all part breds infected with Skowronek.
You are drawings conclusions based on genes about Arabian ancestors (Rodania and Mesaoud) from known part breds. Does that make sense?
I’m not sure YOU know what this means, Lyman. All of these named White Spotting mutations are from families of horses that have a known founder — the horses named. Skowronek wouldnt have any of these specific mutations because they didnt exist when he was alive.
What we are inferring, is that (the general) we are discovering new KIT mutations as we go, and it’s likely that horses like Mesaoud and Rodania had some OTHER form of a KIT mutation because it’s obvs not Tobiano and its not any of the identified KIT mutations.
If it helps, think of those horses as the Whalebone of KIT mutations.
So I took Edouard’s question to mean this: Here is a horse with just a trickle of non Arabian blood, .2% according to allbreed and he looks like he does.
Marbon Masterpiece or Fenwick Orion also have small amounts of non Arabian blood. Let’s say under 1%. Can such a small amount of non Arabian blood cause such prominent markings?
Lyman, what I understand now, and it’s been an immensely enriching discussion (thank you Michael, Moira, Kate, others) is that the tobiano gene in Royal Court Jester (where the white goes around the back of the horse) is: a) not present in Arabians, and b) different from the genes that Marbon Mastarpience and Fenwick Orion and others display.
Lyman, what I understand now, and it’s been an immensely enriching discussion (thank you Michael, Moira, Kate, others) is that the tobiano gene in Royal Court Jester (where the white goes around the back of the horse) is: a) not present in Arabians, and b) different from the genes that Marbon Mastarpience and Fenwick Orion and others display.
Also, the tobiano gene is dominant. One of the two parents has to be tobiano. One of two parents of the tobiano parent has to have it, and so on.
Here you will find photos of Awestrukk, one of the most extreme sabino stallions i have seen in pictures so far.
https://www.facebook.com/pg/blackdiamondarabians/photos/?tab=album&album_id=522655991134428
Moira- I would love to read the study. Post a link to it.
No, Lyman. The tobiano gene is a dominant mutation that can be traced right back through the pedigree.
The idea that “impure breeding” can be detected by the later occurrence of coat color variations (as opposed to something like tobiano which is introduced by the cross itself) is a pre-scientific model, not a biological one.
Michael-
I understand the tobiano issue, but can you explain this a bit more:
“There are a number of genes (genetic locations or loci, singular locus) which influence the development of white markings, and I know of no research into how to recognize the DNA-level cause of the kinds of Arabian phenotypes Edouard has been posting. It is possible that some of them result from other changes at the same genetic location as tobiano, but then again there’s no evidence for that, either.”
How do you know that the small level of non Arab blood in their pedigrees is not responsible for the white markings they display? Biologically.
I just wrote: The idea that “impure breeding” can be detected by the later occurrence of coat color variations (as opposed to something like tobiano which is introduced by the cross itself) is a pre-scientific model, not a biological one.
I literally do not have time for this.
IIRC, Fenwick Orion was W20/W20.
As others have mentioned, white markings are complicated. It would be interesting to start compiling some photo pedigrees for comparisons of markings and color among ancestors.
Beth – allbreed kinda has that feature, but the pedigrees need to be accurate, and photos need to be uploaded.
So here’s my takeaway from this whole discussion:
Modern genetics can basically tell us absolutely nothing about which ancestor of Marbon Masterpiece or Fenwick Orion is the source of their discoloration.
RFR The Iceman – the last time that I talked to this horse’s owner, tested negative for sb1 and he did not test positive for any of the known white spotting genes. Possibly in another mutation. He has two blue eyes.
Lava Ridge Poteka – http://www.grm.net/~pandemo/punc/tiki/tiki.html
Moonlight Money Maker had some really intense foals, but iirc there was a scandal with one of the breeder’s horses papers being pulled, so, this could be questionable. I believe the breeder of was also arrested for animal cruelty charges, and a lot of these places are lost or deceased, in any case.
Approaching this from the opposite corner: where did the idea that “too much white” is an indication of non-Arabian ancestry come from?
I don’t think being W20/W20 is the only reason behind Fenwick Orion’s white markings. W20 works has a “catalyst” for white markings. Some homozygous W20 horses show very standard amount of white. There is quite likely another gene involved here that we don’t know off yet. KIT gene is only part of puzzle. It could be something on MITF or PAX that is not yet identified.
Jenny-
I think the simple answer to your question is that it is a reaction to Skowronek.
The notion of “too much white” comes from the observations among breeders of horses considered “Asil” in many countries, but especially those countries where the influence of Skowronek was especially high that white markings are a sign of impurity.
It’s an overreaction in my view. It is a question of degree.
This feeling appears to be especially entrenched in the SE community. If you read the books of Judith Forbis and Hans Nagel you will see views like this. The Egyptian Alternative books also mention this, and push back a bit on it, but still reflect a large bia away from chestnuts and towards grey horses where white markings are not as noticeable.