204 MUTATION AND PLANT BREEDING 



1937. Resistance of sorghums to the chinch bug. U. S. Dept. Agr. 

 Tech. Bui. 585. 



35. Snowden, J. D. 1936. The Cultivated Races of Sorghum. London: 



Adlard and Sons. 



36. Stephens, J. C. 1937. Male-sterility in sorghum: Its possible utiliza- 



tion in production of hybrid seed. Jour. Amer. Soc. Agron., 29: 

 690-696. 



37. . 1946. A second factor for subcoat in sorghum seed. Jour. 



Amer. Soc. Agron., 38: 340-342. 



38. . 1956. A breeding method to eliminate tall mutations 



in combine grain sorghum. Texas Agr. Exp. Sta. Tech. Article 

 2522. 



39. and Holland, R. F. 1954. Cytoplasmic male-sterility for 



hybrid sorghum seed production. Agron. Jour., 46: 20-23. 



40. , Kuykendall, G. H., and George, W. W. 1952. Experi- 

 mental production of hybrid sorghum seed with a three-way cross. 

 Agron. Jour., 44: 369-373. 



41. , and Ouinby, J. R. 1938. Linkage of the Q B Gs group 



in sorghum. Jour. Agr. Res., 57: 747-757. 



42. Tullis, E. C. 1951. Fusarium moniliforme, the cause of a stalk-rot 



of sorghum in Texas. Phytopathology, 61: 529-535. 



43. Vinall, H. N., Stephens, J. C, and Martin, J. H. 1936. Identifica- 



tion, history, and distribution of common sorghum varieties. 

 U. S. Dept. Agr. Tech. Bui. 506. 



44. Wagner, F. A. 1936. Reaction of sorghums to the root, crown, and 



shoot rot of milo. Jour. Amer. Soc. Agron., 28: 643-654. 



Comments 



Gabelman: You assumed the wild-type genes for maturity were prob- 

 ably all recessive and that the selection in the tropics was in favor of 

 the dominant genes. Under what photoperiods would this natural selec- 

 tion have taken place? Do you assume that this is selection brought 

 about by domestication, or was it natural selection? 



Quinby: It seems reasonable to suppose that late maturity and large 

 size resulted from domestication. Photoperiodic response is influenced 

 by temperature and floral initiation would be delayed even with 12-hour 

 days at some temperatures. Snowden, in his book "The Races of Sor- 

 ghum", presents evidence that leads him to believe that present-day 

 varieties evolved from grassy types. However, my opinion in regard to 



