456 Plant-Breeding 



7. Make a transmission curve from the data on the accom- 

 panying sheet. Which progeny units would you select for breed- 

 ing purposes? How do you account for the apparent discrep- 

 ancies which occur, such as the cases where the offspring give a 

 very different yield from their parents ? 



8. Taking into account the number of tubers per hill, weight 

 of tubers per hill, number of marketable tubers per hill, and 

 weight of marketable tubers per hill, select the best 25 four- 

 hill-units. Tabulate these, giving their progeny number and 

 data for number of tubers per four-hill-unit, number of market- 

 able tubers per four-hill-unit, weight of tubers per four-hill-unit, 

 and weight of marketable tubers per four-hill-unit. 



9. Give briefly your reasons for selecting the above four-hill- 

 units. Draw Galton curves for these 25 four-hill-units, showing 

 variation in the number of marketable tubers per four-hill-unit 

 and weight of marketable tubers per four-hill-unit. 



10. Determine the possible yield of marketable tubers from 

 an acre of the highest and lowest yielding of the 150 four-hill- 

 units, also for the highest and lowest and for the average of the 

 25 selected units. 



11. Give a short summary of results as shown by the con- 

 stants and curves and their bearing on your final selection. 



12. Give direction for starting a potato breeding-plot. 1 



Potato Data for making a Transmission Curve 



The following data have been obtained by the method out- 

 lined above. They represent the weights in grams of parent 

 hills and the average weight of their corresponding progeny. 

 The parent hills have been listed in the order of their weight 

 from lowest to highest (forming a Galton curve). 



1 Reference : H. J. Webber, "Plant Breeding for Farmers." New 

 York Agr. Exp. Sta., Cornell University, Ithaca, N. Y., Bull. 251 : 

 162-171, 1908. 



