INCREASING THE SUPPLY OF PARENT CORN— the third step 
A fter new pioneer hybrids demonstrate and prove their 
superiority throughout the testing period lasting from three to 
five years, they are ready for commercial production. 
But before a new hybrid can be produced on a large scale, an 
increase must be made on the supply of seed for the inbreds which 
make up its parentage. 
Each of the four original inbred strains is planted in isolated fields 
located 40 or more rods from the nearest corn field to protect the 
plots from foreign pollen. 
The seed harvested from the four fields is used to plant the four 
inbreds we will call A, B, C and D. These are then cross-bred in pairs 
to produce two "single crosses.” 
To produce a "single cross,” Pioneer corn breeders alternate one 
row of Inbred A (male) with two rows of Inbred B (female) all 
through a field. The female is detasseled to prevent self-pollina¬ 
tion. The pollen from the tassels of male Inbred A cross-pollinates 
the silks of female Inbred B. 
Inbreds C (male) and D (female) are hybridized in the same man¬ 
ner. Seed picked from female rows B and D grows two different 
"single crosses” which are then crossed to make the final "four-way” 
hybrid crosses. 
lOP—A FIELD SHOWING TWO STRAINS OF INBREDS, A AND B, BEING CROSSED 
BOTTOM—A CROSSING FIELD OF TWO OTHER STRAINS OF INBREDS, C AND D 
