452 Plant-Breeding 



Red pericarps may conceal purple aleurone. 

 Purple in aleurone over red in aleurone. 

 Starchy over non-starchy. 



EXERCISE 22 

 A Study in Potato Selection 



Purpose. 1. To teach the essential characteristics of a good 

 tuber and a good tuber-line. 



2. To teach the principles of selection by a study of variability 

 in pure tuber-lines. 



3. To demonstrate the tuber-unit method of potato selection. 



4. To study variability by means of biometrical data, and 

 the interpretation of constants and curves derived therefrom. 



5. To fix in mind how the hills of different weights look. 



6. To calculate the theoretical weights per acre when given 

 certain weights per hill. 



First Exercise 



Materials. Printed directions and sheets for recording data. 

 Manila paper bags, size 12, for containing product of each hill. 

 Cloth bags for carrying a number of these small bags when filled. 



A breeding plot planted by the 4-hill tuber-unit method, 

 that is, each four hills having the same progeny-number should 

 come from the same mother tuber, and they should be planted 

 and staked so that the progeny of each hill and unit can be 

 distinguished. 



This plot should be planted in good soil and given excellent 

 care throughout the season as its usefulness to the class will 

 depend entirely on the condition of the crop at harvest time. 

 The rows and tuber-units should be labeled carefully and accu- 

 rately in a convenient way, so that they may be made an object 

 lesson in record-keeping. 



