Planting Seeds & Making Selections
Grape Breeding Program Information
Bruce Reisch's Page
NYSAES Home Page
on each image to see an enlarged version.
Authored by: Bruce I. Reisch and
Philip Stewart, 2001.
Male variety in flower
Step 1: Pollen
If the variety to be used
as a male happens to be in flower at the same time as the female
(in grape breeding lingo, they "nick"), then this step
can be easily accomplished by collecting a few of the flowering
clusters for pollen. However, differences in timing require other
approaches. If the male is significantly earlier, it may become
necessary to collect and store pollen. This can be done by drying
the clusters (1-2 days) and shaking out the pollen onto a sheet
of glass or other smooth surface, then collecting it into a vial
by scraping the glass with a razor blade. If, however, the male
flowers after the female, then the pollen must be
collected, dried, and stored in the freezer (at -20 C / 0 F) and
the cross made next year. Stored pollen usually remains viable,
but it is often not as effective as fresh pollen. Another option
where the male flowers before the female is to reverse the cross
- use the male as a female and use the female as a male. This only
works if both parents have perfect flowers.
Cluster beginning to flower
Removal of the "cap" for
Emasculated flower cluster
Step 2: Preparing
Each flower cluster on a grapevine may hold from
dozens to hundreds of individual flowers. All steps described here
must be applied to every flower on clusters chosen for pollination.
The guiding principle in preparing female flowers is to prevent
accidental pollination before the application of pollen from the
selected male parent. Before the flowers open, each one is covered
by a cap, short for calyptra. Though this cap eventually dries and
comes off on its own, it must be removed a day or two before the
cross is to be made to prevent self-pollination with perfect-flowered
varieties. In most cases, the anthers can, with some care and practice,
be removed at the same time as the calyptra, using forceps with
very fine tips. This practice is called emasculation. After the
cluster has been emasculated, you must wait one to four days before
proceeding (more time in cool weather and less time in warm weather)
so that the female parts of the flower mature further and attain
peak receptivity. This is often indicated by the appearance of a
bead of moisture on the stigma. During this time, the cluster is
covered with a bag to prevent fertilization by external pollen sources.
If the female variety produces female (imperfect) flowers, no emasculation
is necessary. The flowers are covered with a paper bag until they
are ready for pollen application.
Pollination with an entire cluster
Applying stored pollen with a brush
Step 3: Making the
Crossing is often simply a matter of brushing the
pollen onto stigmas of the emasculated cluster. If both parents
are flowering simultaneously, the pollen-bearing cluster can be
gently brushed against the emasculated female. However, if pollen
was collected earlier and stored, application with a soft paint
brush is recommended. Care must be taken to sterilize the brush
(and your hands) with 70% ethanol between pollinations.
After pollen has been thoroughly applied to a cluster,
taking care to brush every flower, the paper bag is replaced over
the cluster, both to prevent fertilization by other pollen sources,
and to protect the developing fruit from birds and the elements.
The bags also help to identify the cluster locations at harvest
time, at which time the seeds are removed from the individual berries.
All material Copyright © Bruce I. Reisch, 2001