176 



BREEDING CROP PLANTS 



hybrid segregation. In some crosses, studied independently by 

 McLendon (1912) and Balls, between the dominant fuzzy-seeded 

 and the recessive smooth-seeded forms, evidence was found of a 

 single-factor difference as well as a two-factor difference. Balls 

 also discovered that long fiber was dominant to short and that 

 but one main factor difference existed. Likewise a dominant 

 long petal crossed with a recessive short petal gave in the F 2 

 generation a 3:1 segregation. In a cross between Egyptian 

 (Abassi) and Texas Upland, Balls obtained transgressive segre- 

 gation in height of plants. Similar results were secured in 

 studying the inheritance of date of flowering and weight of seed. 

 The results of the study of weight of seed are of general interest. 



0.050 0.100 0.150 Gram 



FIG. 42. Seed weights of parent varieties, King and Charara, and Fi and Ft 

 generation crosses. (After Balls.) 



In a cross of Afifi and Truitt, where the mean seed weights of the 

 parents were 0.105 g. and 0.135 g. respectively, the weight of the 

 Fi was 0.165 g. Weights in /^varied from 0.08 g. to 0.175 g. The 

 light-seeded forms bred comparatively true in F z although differ- 

 ing somewhat in means. The larger-seeded types bred true in 

 F 3 or segregated, giving both large-and small-seeded forms. An 

 illustration of this sort of behavior for the parents, FI and F 2 

 generations, is given in figure 42 diagrammatically. As has been 

 pointed out, length of lint is also inherited and in some cases 

 segregation approaches a simple 3:1 ratio with long lint as the 

 dominant character. Later generations 'in some crosses gave 

 pure parental types as well as other lint lengths which appeared 



