Krys,
I have worked with buff orpington and from the results I obtained, I do not think the buff birds I had were dominant white. I also came to the conclusion that my buff orpingtons were wild type. That does not mean that other buff birds do not contain dominant white or are another E locus. In Carefoots study of buff rock bantams, he found that the birds he used were Db, Co and heterozygous for dominant white. I have only seen the abstract on this study.
Brumbough and Hollander determined that the buff minorca was ey/ ebc or ey/ey, s+/_ or s+/ s+, Mh/Mh, Co/Co, Di/Di, Cb/Cb. They crossed the buff minorca with a red jungle fowl so all of the offspring were heterozygous wild type/recessive wheaten or wild type/ buttercup. He did not do crosses with eb brown(partridge) birds.
I have not seen any studies dealing with the delaware. But have hypothesized that delaware are eb/eb, S/S Co/Co, B/B or B/_ based upon Smyth's observations and comments. None of the Smyth's studies dealt with silver in their crosses all of the birds were sex linked gold.
In crosses I have performed using rhode island red female and on barred rock males, then back crossing the F1 males to rhode island red females: columbian restricted, recessive wheaten and silver females and males segregated in the back cross offspring and a few other color patterns. The amount of red pigment in the female birds ranged from almost none (heterozygous Mh/mh+)to over 1/2 of bird being red (Mh/Mh). Hutt and other researchers refer to this red as autosomal red.
Delawares may contain undocumented genes that inhibit the expression of autosomal red, if delaware did not have these genes then they would have red in their plumage. Another example is the difference between silver duckwing OEGB and gold duckwing OEGB. That gold in the wings of the male is autosomal but you can not tell the difference between a female gold duckwing and a female silver duckwing. Either that or they do not have autosomal red in them. I believe that the lack of autosomal red has something to do with the eb allele. My autosomal red, silver, and columbian restricted birds carried mahogany, heterozygous or homozygous, but were homozygous recessive wheaten and did not carry eb. I hypothesized that the delaware and buff orpington cross would produce offspring that were eb/ey or eb/e+.
I said that the females would be like the delaware. It would have been better to have made the statement that the females would be barred, silver and columbian restricted. But that may not mean anything to the forum members that are not well versed concerning chicken genetics.
It is possible that the female offspring will contain very light buff in their dorsal plumage. My thinking was the eb gene plus the undocumented gene(s) would effect the expression of the autosomal red. But then again I may be wrong.
I have limited space and can only perform experimental crossing on a limited bases. This fall I will be doing a cross of the female silver, autosomal red, columbian restricted birds with their sibling males to see what happens with the autosomal red.
Tim
Smyth. J.R., Jr., Somes. R.G.,Jr., 1965. A new gene determining the Columbian feather pattern in the fowl. J. Hered. 56: 151-156
Smyth. J.R., Jr., 1976. Genetic Control of Melanin Pigmentation in the Fowl. National Poultry Breeders Roundtable. p69-86.
Brumbaugh JA, Hollander WF, 1966. Genetics of buff and related color patterns in the fowl. Poultry Science. 45:451-457
W. C. Carefoot., 1995 Evidence that the eumelanin restrictor genes (Co) and (Db) are present in the genome of the Buff Rock bantam
British Poultry Science, Volume 36, Issue 2 May , pages 205 - 207