Hayes and Garber - Cucurbit Breeding

CHAPTER V
CONTROLLING POLLINATION
Methods of controlling pollination have received considerable
attention. Protecting self-fertilized plants from occasional
natural crosses would seem to be a necessity in careful studies
of heredity.
The lack of technic of crossing may be a cause of
failure to improve a particular crop. This entire field is one in
which actual practice is needed before the worker can hope to
accomplish best results. A few general principles will be given.
Selfing Plants Artificially. Certain methods have already
been worked out for particular crops. As an example, in the
tobacco crop artificially self-fertilized seed may easily and cheaply
be produced. The practical grower can well afford to save
his seed by this practice. Before any of the blossoms have
opened, the terminal inflorescence should be covered with a
manila paper bag. The 12-lb. size has been found satisfactory
for this purpose. If a few flowers have already been pollinated
these may be removed before bagging. After a week or 10 days
has elapsed, the bag should be taken off and all flowers except
from 50 to 60 removed and the dead corollas shaken off. After
sufficient flowers have been fertilized the bag may be removed, as
the seed will mature somewhat more rapidly than when enclosed.
Self-pollination of the tomato may be accomplished in very
much the same manner as with tobacco. Small-sized bags are
needed.
In this case it is necessary to jar the flowering branches
upon which the bags are placed as the tomato does not set seed
freely unless some such practice is followed.
Artificial self-pollination in corn is very easy. The ear and
tassel may each be covered with a 12-lb. manila paper bag.
It is necessary to cover the ear before any of the silks show.
Foreign pollen accidentally enclosed with the tassel will not
function after a period of more than two days. Approximately
two to five days after the ear has been bagged the silks will have
grown out and will be ready for pollination. The most favorable
time for pollination is when the silks are 2 to 3 in. long, although
the silks are receptive when much longer.
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