Illustrated Guide to PBGV Color Genetics
This is very much a work in progress and is still rough around the edges. The information herein should be considered tentative rather than authoritative, and is certainly open to discussion.
Introduction to canine color genetics
Color in the PBGV breed standard
The FCI breed standard defines the desired colors by reference to the standard of the Grand Basset Griffon Vendéen, which states: “solid colored: darker or lighter shades of tan, hare-colored, or grayish white; two-colored: white and orange, white and black, white and gray, or white and tan; tricolor: white, black and tan, white, hare-colored and tan, or white, gray and tan.”
The American Kennel Club breed standard defines the desired colors as “white with any combination of lemon, orange, black, tricolor or grizzle markings.” A very similar definition (omitting the mention of black) is used in the rest of the Anglo-Saxon dog world (Canada, U.K., etc.). These standards do not accept the solid colors which, with one notable exception, are now deprecated even in France and rarely if ever seen.
The only PBGVs found today with no white in their coat are the controversial “black and tans” of Mr. René Tixier, a color presently accepted only in France.
The majority of PBGVs show the typical piebald spotting pattern and are therefore probably spsp. The variation in the extent of the white color can probably be accounted for in most cases by plus and minus modifiers, but some dogs with especially little color may be spsw or even swsw. Although rare, solid colors are possible and such dogs must be S-.
Most of the breed’s color variation can probably be attributed to alleles in the agouti series. It is easy to find dogs displaying the classic sable (Ay), saddle (asa) and tan-points (at) patterns, and various intermediate patterns may be due to combinations of these alleles, or to modifiers. While it is likely that dogs referred to as “orange” and “lemon” are merely a variation on the sable theme, the possibility of recessive yellow (ee) cannot as yet be eliminated.
The genetic make-up of black and white PBGVs is not so obvious. Hypothetically, they could be dominant black (As-) or recessive black (aa), although it has been suggested that they might also be tan-points (atat) with so little tan color that it is overlooked, or with a tan color so diluted as to appear white, or possibly with white markings in all areas that might otherwise be tan colored.
If we were dealing with dominant black, one would expect black and white dogs to have at least one black and white parent. My database records 14 PBGVs registered as black and white and for whom the color of both parents is known. Of these, five were born of two parents registered as white, black, and tan; two were born of one white, black and tan parent and one sable parent; and seven others were born of one white, black and tan parent and one white and orange parent. The fact that none of these 14 dogs had even a single black and white parent suggests that we are not dealing with dominant black.
On the other hand, if our black and white dogs were due to recessive black, all the offspring of two black and white dogs should also be black and white. My database records five dogs that were born of two parents registered as black and white. All five were registered as white, black, and tan. This suggests that we are not dealing with recessive black either, and tends to support the “hidden tan” theories.
The breed displays a significant variation in the depth of the tan coloring, ranging from a very pale or lemon color through to a very dark or mahogany color. Whether this variability is due to the action of rufous polygenes alone or in concert with alleles in the brown (B), dilution (D), or albino (C) series will require further investigation. Lighter nose pigmentation suggestive of a bb dog is known to occur, but most often this affects only part of the nose, and occasionally nose pigmentation in these lighter areas will vary in shade depending on the season (winter nose) or will be lacking pigmentation altogether (dudley nose.) Pigmentation of the irises can vary from dark brown to light amber, but dark eyes are not always associated with dark coats, nor vice versa.
As for the remaining genes, the action of the greying (G) and ticking (T) genes are clearly visible in some dogs, but I am aware of neither brindling (Ebr) nor merling (M) occurring in the breed.
This dog is typical of the tan-points phenotype as all the strategic tan-points areas are present: above the eyes, on the cheeks and under the ears, under the tail, and around the anus. Because the extent of the tan areas is quite limited, they are difficult to see even in the full-size photo. There is some sabling present on the head, and this seems to be typical in the breed. (I’m now rethinking this initial evaluation since, in some photos–he doesn’t live with us and I haven’t had a opportunity to examine him in person since starting this project–he looks like a very dark sable: the coat is black along the spine but turns more sable towards the extremities. But he was born a tan-points! Perhaps he’s a sable/tan-points heterozygote???)
This dog is a very clear demonstration of the saddle phenotype, where the young dog appears very similar to the tan-points but the head fades gradually to a tan color as the dog matures. (Same comment as for the previous dog.)
This is nine-month old bitch that displays typical markings for a tan-points, but with some sabling of the head; she may in fact be a saddle. The black areas of her coat already show clearly the effects of the greying gene.
Perhaps she is a tan-points/saddle heterozygote? She also exhibits the effects of the greying and ticking genes, the latter barely perceptible behind the shoulders.