Hayes and Garber - Cucurbit Breeding

284 BREEDING CROP PLANTS
METHODS OF SEED PRODUCTION
After obtaining the better variety for the locality, the seed
grower has the problem of keeping this variety in the same high
state of production and if
possible to improve it. The purpose
of this chapter is to outline methods for the various crops which
may be used by the seed grower or by the average farmer.
Farm crops may be placed in four groups according to their
modes of reproduction. There is a close relation between this
characteristic and the farmer's methods of seed production.
The four groups mentioned are as follows:
Group 1.
tobacco.
Group 2.
Group 3.
Group 4.
Generally self-fertilized: Barley, wheat, oats, peas, beans, flax,
Often cross-pollinated: Corn, rye, most grasses, root crops.
Cross-pollination obligatory: Red clover, sunflower.
Vegetatively propagated: Potatoes, sugar cane, sweet potatoes.
Among farm crops,
the production of seed generally depends
on a union of the male reproductive cell, contained in the pollen
grain, with the female reproductive cell the egg cell.
The pollen grains of corn are produced in the tassel and each
thread of silk leads to an ovary which contains the egg cell. In
order to produce seed, the male reproductive cell must pass down
through the silk and unite with the female cell. This process is
called fertilization.
If pollen and silk are borne by the same plant
the process is self-fertilization, and if
by different plants, cross-fertilization.
As the egg cell and the pollen grain of self-fertilized
plants are, as a rule, alike in their inherited characteristics, the
progeny of a single self-fertilized plant, such as barley, wheat, or
oats, have the same inheritance. There of is, course, considerable
variation in all characters, owing to environmental effect, but all
evidence shows that these differences are not truly inherited.
Occasional crosses occur in self-fertilized crops which cause inheritable
variability. Mass selection serves to eliminate these off
types.
SEED GROWERS METHODS FOR SELF-FERTILIZED PLANTS
For self-fertilized plants the grower can, as a rule, obtain a
The
is to save seed in such
pedigreed strain which is nearly adapted to his conditions.
only thing that he can do with this variety
a way that mixtures of other strains or occasional crosses are
eliminated, together with obnoxious weed seeds and diseases.