BASIC COLOUR GENETICS By Robert Bennion
Basic Pigeon Colour Genetics By Robert Bennion The starting point for colour genetics is the blue bar or wild type as depicted by the European Rock Dove, Columba livia, generally accepted as the ancestor of the domestic pigeon (other races of the Rock Dove have plumage variations.) This is the point of reference for all mutations of the domestic pigeon, they are dominant, partially dominant, recessive or partially recessive to this colour and pattern. In these notes only genes relevant to the Roller pigeon, flying or show, in the Ash-red – BA * Brown – b * Almond – St * Faded - StF * Dilute – d * Recessive red – e Indigo – In Dominant opal - Od Spread – S T-pattern chequer - CT Dark chequer – CD Light chequer - CL Chequer - C Grizzle - G Tiger grizzle - GT Sooty - so Dirty - V Kite - bronze - K Wild-type blue bar is assigned the symbol + Upper case lettering indicates dominance to wild type and lower case indicates recessiveness to wild type, this scenario is confused slightly by some genes being only partially expressed in the dominant or recessive spectrum. The genes with an asterix, are located on the sex chromosome and referred to as sex-linked genes, the others are autosomal genes – not sex-linked and are located on other chromosomes. The list indicates that some of the sex-linked genes are dominant and some recessive, consequently their method of inheritance varies. The male pigeon has two sex-chromosomes and the hen one. The male pigeon can be two sex-linked colours, for example, he can have two ash-red genes or one ash-red and one brown. He will pass one of these colours to his offspring; if the hen he is paired with is blue (she has only one sex-linked gene) and he has two ash-red genes all their offspring will be ash-red and all the young cocks will carry (be heterozygous for) blue. An ash-red cock carrying blue, paired with a blue hen, would produce ash-red and blue sons and daughters. If the ash-red cock carried brown (paired with a blue hen) the sons would be ash-red, heterozygous for blue and his daughters would be ash-red or brown. If the hen is ash-red and the cock blue, all the sons will be ash-red/blue and the daughters will be blue. Cocks carrying blue can be identified by black flecking, or if carrying brown, brown flecking. Almond is a sex-linked dominant gene, it’s genetic symbol St, assigned it by Christie & Wreight in 1925, actually refers to the characteristic flecking - gesprenkelt; The ‘classical almond’ colouration of the short-faced tumbler is generally what people envisage when ‘almond’ is mentioned. However, ‘almond’ can be extremely variable depending on the genes and modifying factors present. The “classical” almond is generally a combination of kite bronze, heterozygous recessive red, chequer, sooty, dirty and other selected polygenes, it is a complex combination to emulate. Faded (StF) is an allele of almond and is found at the same point on the chromosome, and is also sex-linked and dominant. Homozygous faded cocks are not afflicted by the same eye disorders as homozygous almond cocks. Dilute is a sex-linked recessive gene; a dilute cocks daughters will be dilute, his sons will all carry dilute. A dilute hen will not produce dilute offspring unless her mate is dilute or carries a dilute gene; her sons will inherit the dilute gene from her. Recessive red (e) is an autosomal recessive gene, it is also epistatic, meaning it is capable of covering most of the pigeon colour and pattern genes. Indigo (In) A partial dominant, non sex-linked gene. Heterozygous indigo combined with spread blue (black) will produce “andalusian”, patterned indigo are bronze coloured, homozygous (pure) indigo bar/chequer resemble ash-red. Dominant Opal (Od) A partial dominant non sex-linked gene which has a range of expressions; with blue it can produce white/bars cheqs, at the other end of the colour spectrum minimal bronzing of these areas occurs. Flight and tail feathers show varying degrees of “washing-out” or bleaching. With ash-red variable pinkish expressions can be produced, with brown pale cream colours result. Homozygous dominant opal is not viable, the embryo dies during incubation or the young die shortly after hatching. Spread (S) A dominant epistatic gene. With wild-type blue produces black, with ash-red it produces various shades/expressions of ‘lavender’ and with brown an even brown colour. Spread masks the pattern genes, but they can often be seen through the spread. Good-coloured blacks are dark cheq/T-pattern cheq with colour modifiers such as sooty and dirty. Polygenetic selection in some breeds has resulted in glossy beetle-green blacks. Pattern series The order of dominance is: T-pattern cheq> dark chequer> light chequer> chequer> bar. There may be some identification issues between the different chequers when sooty is present. Grizzle(G) Partial dominant, non sex-linked. Heterozygous grizzle with blue bar produces a ‘salt and pepper expression’. Homozygous grizzles are predominantly white. Tiger grizzle (GT) Partial dominant non sex-linked. Grizzled juvenile feathers moult to white giving a distinct colour/white pattern, homozygous tiger grizzles are predominantly white. ‘Tortoiseshell’ is a combination of grizzle and blue chequer; it may be grizzle (G) or tiger grizzle (GT), the variable bronzing being dependant on other modifying genes. Sooty (so) Recessive non sex-linked gene, produces a pseudo-chequer expression on the shield, probably causes some confusion with the identification of chequer and may not be evident in the juvenile plumage. Dirty (V) Dominant and not sex-linked produces a darkening effect to the plumage. Kite/Bronze (K) Most commonly associated with T-pattern or dark chequer blues, not as evident on ash-red and recessive red although will intensify these colours. Some bars will have varying shades of bronzing. There are various piebald genes controlling white flights, white tail, head markings, etc. The résumé for this article was to “keep it simple”, consequently detailed analysis of the genes discussed was not possible. The internet has a multitude of websites pertaining to pigeon colour genetics; a good starting point is Frank Mosca’s site: http://www.angelfire.com/ga3/pigeongenetics/ Which will link to Tom Barnhart’s and Ron Huntley’s excellent sites. Pigeon colour genetics books: Joe Quinn - Pigeon Breeders Notebook Axel Sell - Breeding and Inheritance in Pigeons Paul Gibson - Genetics of Pigeons WF Hollander - Origins and Excursions in Pigeon Genetics 
MOSAIC