Potato Breeding 77 



Improvement by hybridization 



It is hardly advisable for the practical potato-grower 

 to attempt an extensive improvement of his crop by 

 hybridization. While the method has yielded good 

 results in some cases, there are many difficulties in the 

 way and the results are very uncertain. The major 

 portion of a farmer's potato breeding plot should be 

 given over to tuber-unit tests. If the grower feels that 

 he can spare the time and is willing to risk a failure in 

 his enterprise, it would be of interest and possibly of 

 profit to attempt a few crosses between his better strains. 

 Otherwise this method should be left to the experiment 

 station worker, who has the time to make the large 

 number of manipulations necessary, and who can devote 

 large areas to the growing of the seedlings. 



Plants are hybridized primarily to increase their varia- 

 bility and to furnish more material on which to practice 

 selection. In the light of modern mendelian studies, 

 we have come to look upon hybrids as recombinations 

 of characters present in the parents. Care should be 

 exercised to choose parents having as many desirable 

 characters as possible. Subsequent selections should 

 preserve those plants which combine the largest number 

 of desirable qualities from both parents. Hybridiza- 

 tion usually increases vigor and is often useful in restor- 

 ing this characteristic in weakened strains. 



There are certain conditions which make the successful 

 hybridization of potatoes very difficult. In the first 

 place, there is a strong tendency in most varieties not to 

 set seed. In such varieties, the flowers drop off shortly 

 after pollination. This necessitates making a great 

 many pollinations with the hope that a few plants will 



