HYBRIDIZING WITH CONVERTED
TETRAPLOIDS - PART III
Text and drawings
by Oscie B. Whatley, Missouri
Safe (controlled) hybridizing doesn't come easily. It is inconvenient,
time consuming and, in its process, resembles ornaments on
a Christmas tree.
Every breeder exercises some degree of control. It may be no
more than selecting good parents based on surface qualities
while giving little regard to genetic background.
There may be little or no effort to ensure a cross against
contamination and records will be only a matter of memory.
Successful hybridizers who use this unsophisticated method
must have an intuitive gift, in which case they can rival the
most scientific breeders.
However, those of us less fortunate in not being gifted, must
learn to play the game with accurate information. Not only
must we note trends of our lines but also have reliable records
of what caused them to happen. Building good insight to control
your hybridizing choices must come from detailed observations
and accurate data. Feed your brain junk and junkie directions
are what you can expect in return.
Working with converted tets is challenging and therefore demands
control to avoid being misled. However, the method suggested
here, for controlling your crosses, is not limited to conversions
but applies wherever accuracy may be beneficial.
One might argue that the disadvantages of contamination and
abstaining from pollen storage can be overcome with quantity
and that the lines will not be hurt. However, small hybridizers
(and maybe the large ones as well) will be hurt when they experience
• Where exceptional line improvements
have vague records that cast shadows of doubt as to where
they came from. Knowing the genetic background gives in-crossing
and back-crossing fruitful direction.
• Where one unique seedling
stands out among its siblings and you wonder which bull jumped
• Where seedlings from a converted cross do not show the expected characteristics.
Was it a contaminated cross that took years to determine?
• Where weather, more than your goals, dictates your
• Where good pod parents are used up searching
for viable pollen.
No one can assume that the difficult parents
are the best for future improvements. However, they are much
less explored than the easy parents. Hopefully, some much
needed characteristics are lurking in the recessive genes of
these difficult parents and controlled hybridizing will make
those improvements more accessible.
Refer to the following illustration and let's question each step and the reasons
for using them.
Q-I. Why should we collect pollen, expose it to lights,
and store the ripe pollen 12 hours (perhaps more in some cases)
before the flower opens?
A-1. The highest viability
of pollen occurs when the pollen sac
begins to open. Many
varieties in the garden will have exposed their fluffy pollen
to the elements long before dawn. Collecting before the pollen
is ripe eliminates any chance of loss or insect contamination.
A-2. You will have control of the time for pollen ripening;
even late pollen in the garden can be expedited by exposure
to cool fluorescent lights.
A-3. It will be more convenient to observe when the pollen
sac is opening. Collect and store the pollen immediately
after ripening in a cool dry container which will slow down
the deterioration of its viability. Garden pollen has been
observed to lose half its viability in less than 3 hours
at temperatures above 80 degrees.
A-4. Rare pollen collected and stored properly with cotton
can effect 10 times as
many crosses as using it directly from the stamen.
A-5. To avoid risk of losing your pollen to rain. A water
soaked pollen sac does not
have to be open to be lost.
Note: Pollen can be stored on
opening flowers for one day in the refrigerator without serious
loss of viability. Longer storage on an open flower is not
Q-II. Why use MID [microscopic identification] on the pollen
the night before?
A-1. The morning period for the most receptive conditions
on the stigma is probably limited to a few hours. If you
choose to test by MID at the expense of that time, you more
than likely will miss a lot of good crosses.
A-2. Not only can we determine the ploidy by doing MID in
the evening but viability percentages can also be evaluated.
(This method will be explained in Article IV). Knowing the
ploidy and viability prior to hybridizing can keep a lot
of bad pollen off the stigma of good pod parents.
Q-III. Why store pollen in gel capsules with cotton?
A-1. Gel capsules are readily available from your pharmacy;
they are easy to handle and allow moisture to be transmitted
from the pollen when stored in a dehydrating container.
A-2. It is easy to mark their identity with a felt-tip marker.
A-3. The cotton wad holds the pollen in a manner similar
to snow on an evergreen tree, and releases the pollen to
the stigma in frugal amounts while giving adequate coverage.
Also, the cotton prevents caking when exposed to humidity
during the crossing.
Q-IV. Why protect the stigma with an aluminum foil
A-1. It will provide post-protection from rain
for the time needed to germinate the
pollen tubes that enter the style (approximately one hour).
A-2. The pre-protection from insects with dusty feet is probably
the least considered and most likely the main cause of contamination.
Seeing pods form that I did not pollinate and radical seedlings
among fairly uniform siblings convinced me that contaminated
crosses are far more frequent than we dare to admit.
It would be impractical to use this controlled method on every
cross but surely some crosses can be worth the effort. I temper
my excitement when I know a pod has not had this method of
control, because I must await the bloom to verify the accuracy
of the cross. However, when a rare and difficult cross sets
a pod and safe hybridizing methods have been employed, I get
confident and start counting my chickens a little earlier.
Our final Article IV on Pollen Viability will share a study
and method not previously covered in the Journal. I believe
there will be some new and interesting revelations about
pollen-tube growth and pollen-viability peaks and deterioration
under garden and storage conditions.