24 



BREEDING CROP PLANTS 



There is a dominance in FI of the red seed color (brownish red 

 pigment in one of the bran layers) over the white and a partial 

 dominance of the awnless over the bearded condition. The FI 

 plants will therefore, have red seeds and a slight extension of 

 the awns near the top of the spike. 



The inherited factors may be considered to be R for red seed, 

 W for white seed, B for bearded, and A for awnless. W and R 

 are considered to be located in homologous loci of one pair of 

 chromosomes and B and A in homologous loci of another pair of 

 chromosomes. The FI plants may then be considered as ABWR. 

 The gametes of these FI plants may contain either A or B in 

 combination with either W or R. The different combinations 

 are supposed to occur in equal frequency. 



Wheat (Triticum vulgare) has eight pairs of chromosomes. 

 The factors for bearded or awnless spike and for color of seed are 

 independently inherited. Therefore they may be considered to 

 be located in separate chromosome pairs. In the diagram only 

 two chromosome pairs are shown. 



SOMT/C Ceu 



PAKEHTAL GAMETES 



F, ZYOOTC 



F t GAMETES 



PAREHT }. 

 dwn/ess spiff? 

 White seed 



Bearded spike 

 Red seed 



DIAGRAM 2 



The F 2 plants obtained by the self-fertilization of FI crosses 

 will then be the result of all possible combinations of the gametes. 

 The combination will be illustrated by the Punnet square. 



