8 MASS. EXPERIMENT STATION BULLETIN 316 



A comparison of progeny from matings 5 and 6, where production males and 

 exhibition males were mated to Fi females, indicates a dominant tendency of the 

 light color carried by the production male. Here sex-linked relations do not 

 stand out, however. 



In progeny from matings 7 and 8, where production males and exhibition 

 males were mated to F2 females, the dominant nature of modifiers for light 

 color is very evident. There again appear to be no sex-linked relationships. 



Class 9 hybrids came from such matings as Fi X F2, Fi and parental stock, 

 and others. The plumage color of this progeny was essentially the same in both 

 sexes and in general was similar to that obtained in the F2 generation. 



In general, these data on plumage color suggest dominance of light modifiers 

 for color. The character of the progeny indicates further that color may be 

 restored to the Fi level by mating pure exhibition males on either Fi or F2 females. 

 The general plumage color of Fi hybrids is about intermediate between that of 

 production-bred and exhibition-bred stocks. 



Surface Color and Under Color 



The under color of Rhode Island Reds should be of the same rich red color as 

 the surface plumage. In breeding for color it is important to know whether 

 different shades of surface color are associated with different shades of under 

 color. Table 4 summarizes the combinations of surface and under color found in 

 the exhibition stock and in the hybrid offspring from various types of mating. 



The exhibition stock used in this experiment showed a rather intimate associa- 

 tion between standard surface color and dark under color. In the males 74 per 

 cent of those with standard surface color showed dark under color compared with 

 about 79 per cent of the females. Of the total males, 70 per cent had standard 

 surface color, and of the females 67 per cent. 



In the class 1 progeny, 11 out of 15 standard-colored males also carried dark 

 under color, and the single standard-colored female carried dark under color. A 

 marked tendency is also observed for medium surface color to be associated with 

 medium under color in both sexes. None of the light-colored males or females 

 showed dark under color. 



Fi hybrids of class 2 were characteristically lighter in surface color than Fi 

 hybrids from the reciprocal class as noted in Table 3. There is here considerable 

 association between surface and under color in both sexes. 



If both sexes of F2 hybrids are combined in studying under color, it will be 

 observed that there were 30 light, 150 medium, and 68 dark, or a ratio of approx- 

 imately 1-5-2. By combining the light and the medium classes, a 3 to 1 ratio 

 appears. These facts suggest that under color may show a blending inheritance 

 and that both the light and the dark phenotypes may be homozygous while the 

 medium class is heterozygous for genes affecting under color. An examination 

 of the Fi progeny from exhibition males with dark under color mated to produc- 

 tion hens with light under color showed essentially nothing but medium color, 

 again suggesting a blending inheritance of under color. Several genes appear to 

 be concerned in the inheritance of under color. An association between dark 

 surface color and dark under color still appears in this generation. 



From what has been said regarding the behavior of light and dark under color 

 in crosses, the majority of class 4 progeny would be expected to be medium or 



