Hayes and Garber - Cucurbit Breeding

CONTROLLING POLLINATIO.\ 71
All but the outer florets of eight of the central spikelets are removed.
The upper and lower spikelets are cut off with shears and the
central floret of each remaining spikelet is removed by grasping
it near the top with the forceps and giving a downward pull.
The forceps are then carefully pushed between the palea and
lemma and the flower opened. The three stamens are removed
in one operation,
if possible. Care is taken not to pinch the
anthers too tightly and break them open. Spikes are used in
which the anthers are just beginning to turn yellow. Anthers
from the variety to be used as the pollen parent are removed from
the florets. Experience has shown that it is best to use only
anthers which are ready to dehisce and which open after being
held in the hand or soon after being placed in a watch glass in the
sun. A single ripe anther is introduced into each floret.
Where greenhouse facilities are available, crosses may advantageously
be made in the winter or early spring months.
This method is used extensively by the Plant Breeding department
of Cornell University. When all conditions are favorable,
between 50 and 100 per cent, of crossed seeds may be obtained.
Barley and oats are handled in nearly the same manner as
wheat. With barley it is often necessary to emasculate before
the spikes have entirely protruded from the leaf sheath. The
work is somewhat more difficult, as the flowering parts are much
more tender than in wheat. For this reason forceps and shears
with very fine points and thin blades are needed. Apparently
under certain environmental conditions (Arlington Farm, Va.,
Norton, 1902) and likewise at University Farm, Minn., oat
flowers nearly all bloom in the late afternoon. Artificial
pollination under these conditions is more easily performed in
the afternoon from one o'clock until mature pollen is no longer
easily collected.
Among the difficulties of artificial crossing in the field are unfavorable
weather conditions.
rains prevent work.
Too much rain or long-continued
Jellneck (1918) compared two methods of
crossing wheats: (1) emasculation and pollination by placing a
ripe anther in the floret; (2) emasculating spikes as usual and
tying these with spikes of similar maturity belonging to the
pollen parent and covering with a paper bag. In 1916 method
(2) gave twice as great setting of seed as method (1). In 1917
conditions were very unfavorable and no seed was produced by