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  • Subject: [nafex] Re: Kiwifruit Pollen Viability
  • Date: Sun, 28 May 2000 03:17:58 +0000


This spring we have had cool weather that resulted in an
extended the bloom period of A. kolomikta. Presently,
these cold-hardy kiwifruit plants have been blooming for
two weeks now and this will likely continue into next
week. Normally, the flowering period lasts a week to 10
days. The lowest temperature encountered (at the
beginning of) flowering this spring was 29 degrees F
under breezy conditions. Temperatures steadily fell
during the night. Fortunately, this low occurred at
sunrise and temperatures quickly rebounded above the
freezing mark so little damage was done except to the
tips of some potted A. chinensis plants. Sustained and
prolonged cool, wet weather will likely restrict bee
flight and may limit pollination by these insects.
However, research suggests that pollination during cold
temperatures may in some instances help overcome
incompatibility problems and produce fruit set.

Pollen Viability
If dry, pollen from male kiwifruit plants will remain
viable at sub-freezing temperatures and can be kept for
more than a year. You can use a desiccant such as
calcium chloride (Damp Rid) or anhydrite (Drierite) to
remove the moisture. The latter is a more effective
desiccant. Here in Minnesota, kiwifruit pollen is
extracted, dried, and stored using the following
procedures. This approach can be modified to store
pollen from other fruit plants as well.

1) Pick newly opened flowers from male plants. The late
afternoon on a sunny day is a good time to remove these
blossoms as the pollen has generally reached sufficient

2) Snip the anthers from opened blossoms using manicure
scissors. A non-stick (weighing) paper placed on a
saucer plate is a useful receptor/catcher for the

3) Place the plate in a Ziplock-type bag containing the
calcium chloride. Seal, and store overnight.

4) Transfer the dried anthers to gelatin capsules. The
weighing paper can be used as a “funnel” to facilitate
the transfer.

5) Spoon the Drierite into the bottom third of a 40-ml
vial. Place a polyester “cotton ball” swab on top of
the granular desiccant to keep it in place. Fill the
remainder of the space with the gelatin capsules, cap
and seal.

6) Label and date the vial(s) and place them in a small
Ziplock-type bag. Store the bag in the refrigerator for
one day to remove any residual moisture. Then transfer
the vials to the freezer for long-term storage.

Most of the materials mentioned above can be obtained
from your local discount store or pharmacy. Gelatin
capsules may also be available at veterinary-supply
stores or health food-type shops. The weighing paper
and Drierite is available through laboratory-supply
stores or catalogs. Drierite can be regenerated by oven
baking to convert the moisture-containing gypsum back to
anhydrite. The 40-ml vials can be obtained from
environmental laboratories and possibly from some
environmental consulting firms as they are used in the
collection of groundwater samples used for volatile
organic compound (VOC) analyses. Politely ask for any
unused vials that were brought out into the field. As a
word of caution, many of the 40-ml vials usually contain
three drops of concentrated hydrochloric acid as a
preservative. With gloves, carefully rinse the vials
out with water and dry thoroughly. Incidentally, the 40-
ml vials are great for seed storage too!

Controlled Crosses
In Minnesota, A. kolomikta is the first Actinidia
species to bloom and is the focus of fruit-breeding
efforts due to its cold-hardiness. Due to its early
flowering period, interspecific crosses involving A.
kolomikta (as the seed parent) must use either shipped
pollen or dried, frozen, year-old, pollen. Controlled
crosses can be made with kiwifruit by bagging female
blossoms prior to opening (e.g., popcorn stage or
before) to keep bees, flies and other pollinators out.
White, wax-lined “donut” bags available at some bakeries
and party-supply shops work well for this purpose and
hold up well in rainy weather. The bag is slipped over
the unopened blossoms, folded at the opening, and sealed
by stapling. Clothespins can also be used to cinch
openings to the cordon and to help support the bag.

Remove the frozen pollen from the freezer and allow it
reach room temperature before opening the 40-ml vial.
Remove one or more gelatin capsules and reseal the vial
and place it back in the refrigerator or freezer. Empty
the contents of the gelatin capsule into a separate
unsealed 40-ml vial so the pollen can rehydrate for an
hour or two. Recap the vial before bringing out to the
field. To pollinate female kiwifruit blossoms in
controlled crosses, carefully remove the bag from the
(now opened) flowers. Shake (side-to-side) the dried
anthers in 40-ml vial to liberate the pollen. The
pollen will appear as a dust coating on the sides of the
glass vial. Dip a small watercolor-paint brush into the
vial to collect the pollen and then gently dab on the
female flowers. Repeat as necessary (Note: making a
buzzing sound is optional). After pollination, the wood
is color-coded using acrylic paint and flagging ribbons
for future identification. A white “donut” bag is then
once again placed over the female blossoms and stapled
until berry set. Crossing information is then recorded
into a field notebook. The paper bags are removed
following berry set.

The preceding methods can be adapted to other fruit
crops. For self-fertile plants anther removal
(emasculation) may be needed. Most kiwifruit plants are
either male or female so this additional step is not

I hope this information is of some use. Hope you get
great yields with your kiwifruit (A. deliciosa-?) plants.


Bob Guthrie

> Does anyone know the temperature at which kiwi pollen is viable?
> It is cool and wet outside today 11°C (52°F).
> I've read that in apples, the temp must be 14°C for the apple pollen to be
> viable.
> Thanks,
> Derry
> Derry Walsh & Bill Chase
> Aldergrove, B. C., Canada
> phone/fax (604) 856-9316
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