QUINBV: MUTATIONS IN SORGHUMS 199 



Other Useful Genes 



Seed color is an important economic characteristic of sorghum. 

 The colors are varied and occur in different layers of the caropsis. 

 (7, 41, 32, 37). The contrasting colors, such as white, yellow, red, 

 and brown, occur as a result of the color content of the epicarp, 

 the thickness of the mesocarp, the presence or absence of a brown 

 testa, and the dominant or recessive condition of a gr e ne designated 

 as S that controls the presence or absence of brown pigment in the 

 epicarp when a brown testa is present. Six genes, exclusive of the S 

 gene, have been reported to cause color in the epicarp. The genetics 

 of seed color in sorghum has been summarized by Quinby and 

 Martin (31). 



All of the possible pericarp colors are not represented by 

 varieties in the United States. Most of the grain produced in the 

 United States is genetically red or pink. Small amounts of white 

 grain are produced. White grain frequently is used as poultry feed 

 as chickens seem to prefer white grain for some reason. True yellow 

 is not represented by a commercial variety in the United States 

 but may soon be as the yellowest yellow endosperm varieties or 

 hybrids have a yellow pericarp. 



Brown seeds result when a brown testa or undercoat is pres- 

 ent along with a dominant spreader gene that allows the presence 

 of brown in the epicarp. When the seeds are dominant red or pink 

 also, the seeds are dark reddish brown. The brown color is caused 

 by the presence of tannin and the astringency of developing" brown 

 seeds is some protection from birds. In Africa, brown-seeded 

 varieties are used to make beer. In the United States brown-seeded 

 varieties are grown only in the humid areas or where birds are a 

 problem. 



Most sorao varieties have brown seeds and the brown color 

 is associated with high tannin content. Atlas and Tracy, two widely 

 grown sorgo varieties that have no brown testa in their seeds, orig- 

 inated as selections from crosses involving brown-seeded and non- 

 brown-seeded varieties. 



Most discolored spots on sorghum grain result from injury 

 caused usually by sucking insects or diseases. When sorghum plants 

 are damaged, any dead tissue becomes pigmented. The spots become 

 blackish brown, reddish brown, or tan in color, depending upon 



