INBREEDING— THE first step 
INBREEDING A STALK OF CORN 
P IONEER CORN BREEDERS employ every scientific method known in plant breeding 
to produce hybrid seed corn of outstanding quality. 
Inbreeding selected open-pollinated corn to itself uncovers varied plant types, some 
offsprings turning out strong and vigorous and others weak and useless. Pioneer breeders, 
each year, discard thousands of weak plants, saving only desirable types for further 
development. 
After many years of careful inbreeding, w'eak and undesirable characteristics become 
weeded out. Only the strongest plant varieties survive the rigorous inbreeding period 
which usually lasts from five to eight years. 
The result is a pure inbred, small and frail in appearance, but uniform and true to 
definite characteristics, such as disease resistance, plant height, stiffness of stalk, heaviness 
of root systt m, size of ear, ear height, and color of leaf. 
An inbred strain remains pure, and breeds true to its characteristics as long as foreign 
pollen does not contaminate it 
InbreGcling separates weak and strong plants. These plants are descendants of 
the same original ear of open-pollinated corn. Only healthy offsprings are saved. 
The Pioneer Company owns the largest and most valuable supply 
bred seed stocks. Shown below are some of the inbred parent strains. 
of in- 
A Pioneer inbred strain showing uniformity of plant 
size and ear height after six years of rigorous inbreeding. 
A FEW PIONEER INBREDS 
