Abstract
This investigation has been attempted to obtain some knowledge of the inheritance of root color in the radish. Five color types are treated in this paper, i.e. white, red, purple, yellow and black. These results may be summarized as follows:
1. In the cross between red and white, and the reciprocal, the F1 is purple, and the F2 consists of 9 purple: 3 red: 4 white (Table 2). Consequently two factors are assumed; (1) R, a factor for production of red pigment, and (2) B, a factor which produces no color alone, but acts in conjunction with R factor to produce purple pigment.
It seems that the genotype of red may be represented by RRbb and that of white by rrBB.
2. When purple is crossed with white, the F1 is purple, and the F2 is in the ratio 3 purple to I white. The reciprocal also supports the single factor concept (Table 3). These facts suggest that the genotype of purple may be designated by RRBB.
3. In the combination between yellow and white, yellow is dominant over white in the F1, and a 3:1 ratio of yellow to white appears in the F2 (Table 4).
4. The F1 of the cross between white and black is black, and the F2 consists of 3 black: 1 white (Table 5). A close 1:1 ratio of black to white is obtained in the back cross generation of the F1×white (Table 6). It is evident that black is a simple dominant to white.
5. In the cross between red and yellow the F1 is purple, and the F2 conforms to the ratio 9 purple: 3 red: 3 yellow: 1 white (Table 8).
6. Upon selfing variety Cincinnati Market gives a few yellow seedlings which soon fail to develop. The F1 of the cross between Cincinnati Market and Golden Ball is normal green, and the F2 consists of two distinctly different families, one of which gives an approximate 3:1 ratio of green to yellow, and the other breeds true for normal green (Table 9). Xa, a factor for normal green and xa, a factor for yellow are assumed. Thus the genotype of Cincinnati Market may be represented by Xaxa.
7. The F1 of the cross between yellow and purple is purple, and the F2 is in the ratio 12 purple: 3 yellow: 1 white (Table 10).
8. Purple is dominant over red in a monohybrid relation (Table 11).
9. The F1 of the cross between red and black is blackish purple, and the F2 ratio is 27 blackish purple; 9 purple: 9 blackish red: 3 red: 12 black: 4 white (Table 12).
10. In the cross between purple and black the F1 is blackish purple, and the F2 is in the typical dihybrid ratio 9 blackish purple: 3 purple: 3 black: 1 white.
11. Black is dominant over yellow in the F1, and a close 3 black to I yellow ratio is obtained in the F2 (Table 15). Black, yellow and white are so related genetically that any two of them taken together give results conforming to a unifactorial scheme. Consequently it seems probable that the factor for black constitutes a set of multiple allelomorphs with two factors for yellow and white.
12. The probable genotypes of root colors in the radish are assumed as follows:
rrBByy white
RRbbyy red
RRBByy purple
rrBBYY or rrBbYY yellow
rrBBYbYb black
In addition to these formulae, C factor for chromogenic substance may be assumed respectively (Table 16).
