920 



SCIENTIFIC AG-RICULTURE 



June, 1922 



presented are of interest since well-known 

 Canadian wheats were used in the experi- 

 ments. 



The data were obtained from the second 

 generation of crosses made in 1919 as fol- 

 lows : 



Red Bobs x Taylor's Wonder 

 Hard Red Calcutta x Taylor's Wonder 

 Hard Red Calcutta x White Bobs 

 Commonwealth x Kitchener. 

 A total of 652 plants belonging to 43 

 second generation (F^,) families were studied 

 in detail with respect to seed colour, seed 

 texture, chaff colour, and awn character. A 

 description of each parent variety is given 

 in Table 1. These descriptions apply only 

 to material grown in the season of 1921 in 

 close proximity to the F, progeny. 



Inheritance of Seed Colour 



Seed colour inlieritance in wheat has been 

 studied for a number of years. Biffin (1), 

 in 190.5. found that crosses between red-seed- 

 ed and white-seeded wlieats produced red- 

 seeded and white-.seeded plants in a 3:1 ratio 

 in F.,. He also noticed that dark red appear- 

 ed to be dominant to light red. In 1911, 

 Nilsson-Ehle (7) reported crosses which, in 

 the Fo, produced 3:1, 15:1, and 63:1 ratios 

 of red-seeded and white-seeded plants, res- 

 pectively. The Howards of India (8), in 

 1912, obtained 63:1 ratios of red to white in 

 crosses of red Indian wheats with American 

 white clubs. Gaines (5), in 1917, found 3:1, 

 15:1, and 63:1 ratios of red to white. He 

 distinguished at least three different shades 

 of red and decided that the degree of red 

 depended upon the number of factors pre- 

 sent. White, being due to the absence of 

 any red pigment, was considered to be the 

 result of homozygous recessiveness of all 

 factors. 



The results obtained for seed colour in- 

 heritance in the present study are given in 

 Table II. 



No attempt was made to differentiate the 

 various reds. The ratio of red-seeded to 

 wiiite-seeded plants in the P\ approached 

 3:1 in some cases and 15:1 in others. From 

 this it is apparent that some of the red- 

 seeded wheats used have one factor for seed 

 colour and others have two. 



In order to obtain a measure of the reli- 

 al)ility of the results it is necessary to know, 

 first, the deviation of each term of the actual 

 ratio of observed results from the cor- 

 responding term of the theoretical (expect- 



ed) ratio, and second, the relationship of 

 this deviation to the probable error of the 

 given term. When a deviation is no greater 

 than the probable error there is a 1:1 prob- 

 ability that it is due to chance, but a devia- 

 tion of three times the probable error would 

 occur only once in 22 times by the laws of 

 chance. For the purpose of determining the 

 significance of the terms of the ratios in 

 this paper, deviations amounting to less than 

 three times the probable error were not con- 

 sidered serious.- The deviations for the 3:1 

 ratios in Table II are rather high yet not 

 large enough to be significant. 



It is of interest to note that in the crosses 

 of Red Bobs x Taylor's Wonder part of the 

 Fo families segregated in a 3:1 ratio for 

 seed colour and part in a 15:1 ratio. It 

 therefore appears that the red-seed parent 

 included two apparently similar strains 

 which differed in their genetic constitution 

 for seed colour, one having a single factor 

 for red and the other having two factors. 

 These two types of segregation were also 

 produced in the Hard Red Calcutta x White 

 Bobs crosses. The genetic constitution for 

 seed colour of a pure line of wheat haying 

 two factors for red would be R R Rj Rj and 

 where only one factor was concerned, it 

 would be R R r, r, or r r R^ R^. Pure line 

 white wheats would be in all cases homozy- 

 gous recessives for seed colour with the 

 constitution r r r^ r,. Since seed colour 

 factors in wheat are evidently inherited in- 

 dependently a cross between two red varie- 

 ties of the constitutions R R rj r, and r r R, 

 Rj^ should produce red-seeded and white- 

 seeded plants in the ratio of 15:1 in the F^. 

 This is precisely the result obtained by 

 Nilsson-Ehle. 



Inheritance of Seed Texture 

 Until recently very little study had been 

 made of the inheritance of seed texture in 

 wheat. In 1915, the Howards (9) found an 

 intermediate condition in the Fj when a 

 vitreous kerneled wheat was crossed with a 

 starchy variety. The F., gave a 1:2:1 ratio 

 of soft, intermediate and hard; Biffin (2), 

 in 1916, obtained a 3:1 ratio in F^, of soft 

 and hard-seeded plants from a cross between 

 a hard-seeded trugidum wheat with a soft 

 Polish variety. Freeman (i), in 1918. se- 

 cured hard, intermediate and soft-seeded 

 plants, from crosses between hard-seeded 

 durums and a soft club. After carrying the 

 cx})eriment through the fourth generation he 



