Potato Breeding 57 



require little else of the grower than their multiplication ; 

 and third, by crossing plants to combine the best qualities 

 of two or more parents in a new and improved variety. 



Improvement of the 'potato by selection 



The principal method of improving the potato is by 

 bud-selection. Potato hills are very variable, and im- 

 provement is made by planting tubers from the best 

 hills. Many of these apparent improvements may be 

 due to some advantage in growth, such as increased fer- 

 tility, more light or moisture and so forth. Of course, 

 this increase is only transitory, and not being inherited, 

 produces no permanent advancement. 



The potato, however, presents variations which are 

 inherited. These are of two kinds, — smaller differences 

 whose inheritance produces a gradual change, and large dif- 

 ferences or so-called "bud-sports" or bud-mutants which 

 immediately become the starting point of new varieties. 



Potatoes differ from most farm crops in their manner 

 of reproduction. They are propagated vegetatively 

 without the intervention of a sexual process like corn 

 or wheat. Each hill of potatoes comes from one tuber or 

 a part of a tuber which was the product of one bud of the 

 mother plant. Hence the entire hill becomes a unit, and 

 hill selection is, in reality, bud-selection. Single tubers 

 cannot be said to be units from the breeder's standpoint. 

 Therefore, it is of supreme importance to take into ac- 

 count the yield of an entire hill and not the presence in 

 it of two or three large tubers resulting in low total yield 

 for the hill. 



So far as man is concerned, the origin of the initial 

 variation is largely chance, but this start or variation 



