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536
BRUCKN•R,
Inheritance
o! WhitePlumage
in Phasianus
INHERITANCE
OF WHITE
PLUMAGE
IN
[Auk
L Oct.
PHASIANUS
BY J. H. BRUigKNER
Plate
•r8
TH• data herewithpresenteddeal with the inheritanceof white
plumagein the Ring-neckedPheasant,Phasianuscolchicustorquatus.
in a previouspublication (1939) the author has pointed out the
scarcityof knowledgeconcerningthe geneticsof this speciesand reported on the inheritanceof an incompletelydominant,autosomal
genefor melanin. A generalreviewof the literature on the genetics
of the pheasantis given in that paper and accordingly
will not be
repeatedhere.
The pheasantfancier has long had blue-eyedwhite pheasantsin
his aviary, but the origin of this variety is apparently unknown.
Occasionallyreports are publicizedof pure-whitepheasantsbeing
shot in the wild.
Whether
such birds result from mutations
occur-
ring in the wild populationor haveescaped
from aviariescannotbe
proven,but the latter alternativeseemsunlikely.
White plumageamongwild specieswhich are normally colored
is not uncommonand albinos have been reported in many birds
as well as in mammals,reptiles,amphibians,etc. In very few birds,
however,is the exact nature of the white determinedand in many
casesthe specimendescribedis not a true albino at all but merely
a bird with more or lessdepigmentationof the plumage. In the
bird with completealbinism melanin is absentin all parts of the
body. The eye appearspink in color becauseof the blood in the
capillariesof the iris and retina. In most white birds the eye is
black, brown, orange, or bluish, and all of thesecolorsindicate the
presenceof melanin. True albinism is rare but birds in which a
coloredeye is associated
with white plumageare common.
During the pastnine years,approximatelya million pheasantchicks
havebeenhatchedat the New York Stategamefarmsand amongthese
but one true albino
has been found.
It
is not uncommon
to find
white chicks,but usually thesehave somepigmenteddown on the
wings. Almost without exceptionsuch chicksdevelopsome pigmentedfeathersas theyassumethe juvenaland adult plumagesand
'pied' birds, not white ones,are the final result.
Inheritanceof color in the DomesticFowl, a speciesin the same
subfamilyas P. colchicus,
may give someindicationof what might
Vol.
•8-•
•94•
a
BRUCI•NER,
Inheritance
of WhitePlumage
in Phasianus
537
be expectedof color in the pheasant. In that specieswhite plumage
may be due to any one of three differentgenes. The White Leghorn
fowl carriesa unifactorial,incompletelydominant,autosomalgene
which inhibits the formation of melanic pigment. Fundamentally
the White Leghornis a coloredbird, but the presenceof the inhibiting gene in homozygous
form preventsthe expressionof black. In
heterozygous
individualssomecolor is evident. This type of white
plumageis found occasionally
in other breeds,but so far as is known
is the result of crossingwith White Leghorns.
The secondkind of white plumage is that found in Plymouth
Rocks,Wyandottes,Dotkings, Langshans,and other breedsof fowl.
This white is autosomaland recessive
and is apparentlydue to the
absenceof a genenecessary
for the formationof melanin. Sincethe
eyesare pigmented in both the dominant and the recessivewhites,
neither
is a true albinism
and both
should be considered
as a kind
of white in which the manifestationof melanin is usually restricted
to the eye. Batesonand Punnett (1908) describedanother 'complementary' white in Silkie fowls, but no other workers have been
able to detect it in that breed.
True albinism is so rare in the fowl that in the thirty-nine years
since the rediscoveryof Mendel's laws only one casehas thus far
been reported. The conditionwas found by Warren (1933) to be
a simpleautosomalrecessive
character.
The white pheasantshowsno signsof pigmentationin the plumage, but beak and shanksare a pearl white and the eyesare blue.
It can be seenthat the white plumageof the pheasantmight possiblybe any one of the geneticallydifferenttypesof white reported
above,or possiblystill another, since in thesewhite pheasantsthe
eyeis blue, a conditionnot found in any of the white fowlsmentioned
above. Moreover,the shank color is affectedin white pheasants
but not in mostwhite fowls. It is possible,
of course,that in these
white pheasantsthe shank-and eye-colordilution are due to other
genescloselylinked with that for white plumage.
In the absenceof definite information of the genetic basis for
white plumagein the pheasantan investigationwas begun in 1938.
While it wasunder way anotherreport of 'hereditaryalbinism'was
found. Taibell (1928)concludedthat white is a monohybridrecessive character. He called his white specimens'albinos',but the
descriptionfurnished indicated that they were blue-eyed whites.
Since his studies were somewhat limited,
port the presentexperiments.
it seems advisable to re-
538
BRVCKN•rt,
Inheritance
of WhitePlumage
in Phasianus
[Auk
L Oct.
GENETIC ANALYSIS
The
first crosses were made in 1958.
A male and two female white
pheasantswere purchasedfrom a fancier with the assurancethat
they had bred true for many generations. These birds had white
plumage,blue eyes,and pearl-white beak and legs. There were no
coloredfeathersanywherein the birds nor did they showany after
the adult
molt.
The male was mated with four Ring-neck females and the two
white femaleswere mated to a Ring-neckmale with the following
results:
Progeny
Parents
Number
White cP X Ring-neck 9 9
Ring-neck cP X white 9 9
89
14
Color
Ring-neck
Ringmeek
This is what would be expectedin the Fx generationif the white
plumagewere due to a recessive,
unifactorial,autosomalgene.
If the character were sex-linked and recessive,that would be shown
by differences
in the progenyfrom reciprocalmatings. The mating
of normal, colored,Ring-neckmalesto white femaleswould then
produceF• progenywith normalplumage,but in the reciprocalmating of whitemalesto Ring-neckfemales,the femaleprogenywouldbe
white, while the male progenywould be Ring-neckcolor. Since
such'criss-cross'
inheritancewasnot found, thesefirstmatingsdemonstratedthe autosomalnature of the gene.
At maturitymostof the F• birdswereidenticalin appearance
with
the Ring-neckstock,but an occasional
bird exhibiteda completely
white primaryor tail-feather. Othershad a patchof white feathers
on the throat but in the majority white was not in evidence. All
progenyhad dark-pigmented
eyes,beak and shanks.
F2 GENERATION
In 1959,the F• progenyof the white • X Ring-neck 9 9 were
matedinter se to producethe F2 generation(pen 1-$9). This was
alsodone [or the progenyof the Ring-neck• X white 9 9 (pen
2-$9). In theseF2 generations
the expectation
was$ colored:1 white,
if the white were a simple,recessive
character. Classifications
at
hatching,includingembryosdying late in which color could be
determined, were as follows:
Vol.
•94t •8]
-•
BRUCKNr•,
Inheritance
of WhitePlumage
in Phasianus
Hatched
Late dead embryos
Ring-neck
White
Ring-neck
Pen 1-39
70
25
25
Pen 2-39
44
13
10
Combined
White
539
Combined
Ring-neck
White
6
95
31
4
54
17
149
48
147.75
49.25
total
Expected (3: 1 ratio)
Taken either separatelyor togetherthesematingsyield an unusually
closefit to the 3: 1 ratio expected. About onehundredoœthesebirds
were reared to maturity and in none oœthem did any oœthe white
segregates
assumethe Ring-neckplumageor showthe pied condition.
It wasnotedthat a numberoœthese(adult) birdshad an occasional
dark feather,particularlyon the head. Conversely,
someoœthe F2
Ring-neckshad an occasional
white feather in the wing or a small
white patch of featherson the throat. Doubtlessthesewere individualsheterozygous
for white. Birds oœthat genotypemust have
comprisedtwo-thirdsof the F2 population,but sinceonly a few oœ
the Ring-necks
showedany white feathers,it is clearthat the white
plumageis usuallycompletely
recessive
in the heterozygote.
The symbolc, which is usedto denotethe genefor recessive
white
in the fowl, is assignedto this gene responsiblefor the absenceoœ
color in the pheasant. The normal wild Ring-necked Pheasant
would thus be CC, while the pure-whitebirds would be cc.
BACKCROSSES
The expectationhere, as in any backcrossto the recessiveform,
wasa ratio of 1 colored: 1 white. Backcross
matingsoœFx progeny
were made to the white male and females. One oœthe original
white hensdied during the breedingseasonand, accordingly,two
additional white hens were obtained from the original sourceoœ
the stockusedin the experiment. The resultswere as follows:
Hatched
Pen 3-39
Pen 4-39
Late deadembryos
Combined
Ring-neck
White
Ring-neck
White
Ring-neck
White
33
61
21
66
21
30
15
15
54
91
36
81
145
117
131
131
Combined
total
Expected (1: 1 ratio)
540
Inheritance
of WhitePlumagein Phasianus
IL'Auk
Oct.
There is a deficiencyof white chicksin both these backcrosses.
Application
of theX5 testfor goodness
of fit of observed
andexpected
ratios (in combinedtotals)yieldsa valuefor X• of 2.992and,with
n = 1, the value for p is .083. This meansthat the deviationfrom
expectation
is not significant,
and, therefore,the hypothesis
that a
single gene causesthe recessivewhite is not invalidated. Dunn
(1923) reported a lethal gene linked with recessivewhite in White
Wyandottefowl. The deficiency
of whitesin thesepheasant
backcrosses
doessuggestthat embryonicmortality is higher in cc embryosthan in Cc ones. However,there was no deficiency
of the
homozygous
recessives
in the F• generation
and the discrepancies
in
the backcrossesshould therefore be ascribed to chance. Since the
deficiency
of whiteswasevidentin theembryos
dyinglate,anylethal
effectof the white in the homozygous
conditionmust have been
exertedin embryos
dyingat somestagebeforethe plumagecolor
couldbe determined.It is noticeable
thatthe majordeviationfrom
theexpected
1: 1 ratiowasin pen3-39,whichyieldeda ratioof 54
Ring-neckto 36 whitechicks,whereas
pen 4-39gavea ratio of 91
Ring-neck
to 81 whitechicks.The latteris a reasonably
goodfit
to the normal
ratio.
Some of the white birds from the backcrosses
showedan occasional
darkfeatherand a fewof the Ring-necks
showed
a whitefeatheror
two aswasthe casein the F• matings.
In orderto checkfurtherthe conclusion
as to the geneticbasis
for whiteplumage,the whitesegregates
fromthe backcross
matings,
pens3-39and4-39,werematedintersein 1940. Two suchmatings
were made with the result that 75 chicks were hatched. These chicks
wereall purewhitewhenhatched,
andat maturityshowed
no signs
of coloredplumage.
DISGUSSION
The sourceof the whitepheasants
as bred in captivityis not
definitelyknown,but, ashasbeenmentioned,whiteindividualsin wild
birdsof otherspecies
arenotuncommon.
Someof these
wildspecimensare true albinos,but they are relativelyrare. Gamebreeders
differin theiropinions
asto theoriginof thisvariety. Some
believe
it
to be a true mutationor 'sport'while othersthink that it is the result
of selectionfrom 'pied' or 'spotted'stock. This latter aberrantform
isrelatively
common.Gorrespondence
with observant
gamebreeders
hasindicatedthat white mutationsfrom Ring-neckand melanistic
pheasantshave been known to occur.
Vol.
sS]
1941
.•
BRUCKNER,
Inheritance
o[ WhitePlumage
in Phasianus
541
It is evident from the data presentedin this paper that white
plumagein the pheasant,Phasianuscolchicus,is due to the presence
in the homozygouscondition of a unifactorial, autosomalgene.
Dominanceof the allele, C, for color, is sometimesincompletesince
heterozygous
individualsoften showoccasionalwhite feathers. Conversely,homozygous
recessive
individualsmay showa slight ticking
or a coloredfeather. Recessive
white segregates
from backcross
matingsbreed true when mated inter se.
It would seemthat white plumagein P. colchicusis similar in
characterto the recessivewhite found in White Wyandotte,White
Plymouth Rocks and other varieties of fowls. However, in the
pheasantthe pigmentin the eye, beak and shank is so reducedthat
thesestructuresappearbluish, whereastheseareasare not affectedin
white fowls. This suggeststhat the genesresponsiblefor white
plumagein the two speciesare not comparableor else,possibly,that
the pheasantcarriesa gene,or genes,for the dilution of eye, shank
and beak color closelylinked with the genec responsiblefor absence
of color in the plumage. However, since in all the white birds
raised in this study no exceptionswere observedto the rule that
white pheasantshave blue eyes, beak and shanks, it seemsmost
probablethat the singlegene, c, is responsiblefor the dilution of
melanin pigment in theseareasas well as for its elimination from
the feathers.
SUMMARY
White plumagein the genusPhasianusis due to a single,autosomal,recessive
gene,c, presentin the homozygous
condition. This
is shownby ratios observedin 103 Fx, 262 backcross,and 197 F2
pheasants
followingcrosses
involvingwhite and Ring-neckPheasants.
LITERATURE CITED
BAaW•SON,
W., Am) PuremEant,R. C.
1908. Experimental studies on the physiologyof heredity. Reports to the
EvolutionCommitteeof the Royal Society,4: 18-35.
]•RUCKNER,
J. H.
1939. The inheritanceof melanismin pheasants.Journ.Heredity,30: 45-52.
DUNN, L. C.
1923. A lethal gene in fowls. Amer. Naturalist, 57: 345-349.
TAIBELL, A.
1928. L'eredita
meridaliana
dell'albinism
in Phasianus colchicus L.
Rivista
di
Biologia, Milano, 10: 695-701.
WARREN, D, C.
1933. Inheritanceof albinismin the DomesticFowl. Journ. Heredity, 24:
379-383.
5't2
BRVCKN•R,
Inheritance
of WhitePlumage
in Phasianus
EXPLANATION
[Auk
L Oct.
OF PLATE 18
UPPERF•CURE:
Normal Ring-neckedPheasant,Phasianuscolchicus,used in study
of the inheritanceof white plumage. Fx hybridsbetweenthis bird and pure-white
pheasantscannot be distinguishedfrom the common Ring-neck except in rare in-
stances
whereone or two main tail- or wing-feathers
may be white.
LowER F•CVRE:Pure-white pheasant used in this study. The white segregates
in the F• and backcross
matingsare identical in appearanceand breedingbehavior
with the original white stock.
Departmentof Poultry Industry
Cornell University,Ithaca, New York
THE
PLATE
AUK, VOL. 58
NORiMALLY
I}URE-WHITE
PLUIMAGED RIN½;-NECKI•]D PHEASANT
RING-NECKED
PHEASANT
USED IN THIS STUDY
18