SIGNIFICANCE IN MAIZE BREEDING 
As the plant breeder begins to reach a point of dimin- 
ishing returns in improving the varieties at hand, he is 
compelled to turn to centers of diversity for new charac- 
ters. The maize varieties of western Guatemala, especially 
the Tripsacoid types, those with high knob numbers, con- 
stitute an untapped resevoir of germplasm which includes 
genes governing the expression of a number of valuable 
characteristics including fibrous root systems, resistance 
to lodging, resistance to smut and perhaps to other dis- 
eases. Here in concentrated form is to be found much 
of the germplasm which occurs greatly diluted in the 
commercial varieties of the United States. 
There are few, if any, varieties in western Guatemala 
which would, as such, be useful for commercial produc- 
tion in the United States. Perhaps a few would have a 
place as silage corn, but even this is doubtful; the stalks 
are too tough to be cut with ordinary machinery. But if 
the breeder is looking, not for varieties but for genes, he 
will certainly find in Guatemalan maize, many which 
may be useful. 
Most of the Guatemalan varieties are characterized by 
extreme lateness in maturity. Whether this character- 
istic is readily separable from others, can be determined 
only by experiment. Unpublished observations by the 
senior author indicate that large differences in time of 
maturity of corn varieties may be governed by a relative- 
ly small number of genes. In crosses of the early matur- 
ing inbred strain P 89 with tall, late varieties of Texas, it 
ras possible in the backcross to P 89 to recover the type 
of ear and productiveness of P 89 with much of the late- 
ness and vigor of the Texas varieties. Also Brunson (un- 
published) has found that the indeterminate growth habit 
of Cuzcoid (a type resembling in its vegetative habit the 
Cuzco variety of Peru) is a simple Mendelian recessive, 
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