82 BREEDING CROP PLANTS 



generation a ratio of 3 red-seeded plants to 1 white-seeded plant 

 is often obtained. Nilsson-Ehle (19116) was the first writer 

 who reported crosses which in F 2 gave 15 to 1 or 63 to 1 ratios of 

 red- and white-seeded plants. The Howards (1912), in India, 

 have obtained 63:1 ratios in crosses of American Club with pure 

 lines of Indian wheats, and Gaines (1917) in Washington, has 

 obtained similar results from a cross between Bluestem (red seed) 

 and Brown's Glory (white club wheat). Nilsson-Ehle obtained 

 a ratio of 15 red-seeded plants to 1 white-seeded plant from a 

 cross of two red-seeded varieties. The inheritance of this seed 

 color has been explained by one or more Mendelian factors, 

 each when present giving red and when absent white. The 

 factors are separately inherited, each when homozygous produc- 

 ing somewhat darker color than when heterozygous. They are 

 also cumulative, two factors giving a darker color on the average 

 than one of these factors alone. It is impossible, by inspection, 

 to determine how many factors are responsible for a particular 

 varietal seed color. 



Texture of seed has also been used in varietal classification and 

 is a character which determines to some extent the market class 

 in which the variety will be placed. Biff en (1916) found im- 

 mediate effect of pollination in a cross of Rivet, a hard-seeded 

 turgidum with pollen from a soft Polish variety. The FI genera- 

 tion plants produced hard seed and the F% segregated into 

 hard- and soft-seeded plants in a ratio of 3:1. The Howards 

 (1915) obtained an intermediate condition inFi plants and a 1 : 2 : 1 

 ratio in F 2 in crosses between hard- and soft-seeded strains. 

 Freeman (1918) crossed hard-seeded durums with T. vulgare, 

 variety Sonora, a soft-seeded wheat. The FI plants produced 

 hard, intermediate, and soft seeds. The hard seeds of the FI 

 tended to give more hard-seeded plants in F 2 , and the soft-seeded 

 tended to give more soft-seeded plants. Freeman carried the 

 study through ^4. He explained his results on the basis of two 

 factors for starchiness, each inherited independently. He 

 supposed each to produce half as much soft starch when hetero- 

 zygous as when homozygous. As the endosperm is the result of 

 the fusion of two polar nuclei with one of the male generative 



FIG. 19. Representative spikes of F 3 families of the cross between Durum 

 and Marquis. Upper 4 groups, Fa families which were classified as durums. 

 Note that they represent all types of spike density. Lower left, spikes of an 

 awnless F 3 Emmer family. Lower right, four spikes of an F 3 plant which re- 

 sembled common wheat in spike shape and which proved rust resistant. 



