HYB: Pollen Viability

From: Sharon McAllister <73372.1745@compuserve.com>

Sterling wrote:

>  I did 
>  manage to find a message from Sharon McAllister regarding using a 
>  microscope to determine if the pollen was still good but she did not 
>  mention the length of time. If anyone knows if pollen can be frozen for 
>  6 months or longer, I would appreciate the help.

The main reason hybridizers have frozen pollen is to carry it over from one
bloom season to the next.  I had enough success is using one-year-old
pollen that after a few years I stopped discarding older pollen of
important breeding stock.  After all, a late freeze could wipe out the
current season's bloom of a special cultivar and I thought that
two-year-old pollen would be preferable to none at all.  That's when I
started using the microscope to check the quality of stored pollen, and
started observing how viability deteriorates with time.  Think of it as a
"half-life" process.

After my earlier post about getting seeds from year-old pollen, I checked
my records and verified that I also got seeds from much older pollen -- up
to four years old.  One-year-old pollen, SOP.  Two-year-old pollen, still
useful.  But takes from three-year-old pollen were sparse, so I used up all
of the '93 supply in '97 tests.  Of course, some had to be discarded, but I
got just enough seedlings to convince me that my use of the microscope to
assess pollen quality had been effective.  

So my practice is to use the freshest available pollen.  When is it worth
storing more than one year?  When it's something scarce, vital to an
experimental line, with no top priority use possible the current year. 

For example, I've been testing some theories of cytoplasmic inheritance. 
One type of cross involves a pod parent whose maternal line can be traced
back to a certain species and a compatible pollen parent that carries as
high a concentration of genes from that species as possible.  Needless to
say, these pairs are hard to come by.  When I've had pollen of this type
left as the season comes to an end, I've saved it for the following year
rather than using it with less desirable mates.

John Jones added:

>  I think the real key is keeping the pollen moisture free. Moisture is
the
>  pollen killer.

Yes, it's the main enemy.   We should probably mention, though, that those
who use modern "frost-free" freezers have reported less success in
long-term storage.  Apparently these are more prone to frost-burn and
therefore kill the pollen by dessication.

Sharon McAllister
73372.1745.compuserve.com

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