[NAFEX] seedless grapes

mauch1 at aol.com mauch1 at aol.com
Mon Nov 21 16:21:22 EST 2005


<<
Ok, so how do they make grapes seedless? A youngster I know asked and 
I'm at a loss a to what the answer is.
>> 
 
Rondi

What I'm about to tell you combines some knowledge, some observation, and some 
supposition.
 
<Sup>  I don't think that seedless grapes are triploid.  I believe the seedlessness
is a genetic defect in the seed development process of grapes.
 
<Kno & Obs> Seedless grape vines 'come that way'.  In general a grape variety is either 
seedless or not (There is a 'Concord seedless'.  It is not directly related to Concord),
but there are varying degrees of seedlessness, some having a large, but soft seed
(Canadice), to almost non-existant remnants (Thompson seedless).
 
<Kno> To get more seedless varieties, they generally breed seedless grapes 
to seeded grapes.  I did read a number of years ago, that they had discovered that
not all seedless grapes remanants seeds are sterile (i.e. I would assume something like
Thompson Seedless would be, but something that has a larger remnant might grow).
So this does open the possibility of 'seedlessXseedless' crosses.
 
<Kno & Sup> Grapes without fully developed seeds, often don't have large 
berries.  Though there are some natural methods of getting the berries to 
size up better (i.e. cane girdling), the grape you see in the stores have often 
been sprayed with a hormone called gibberellic acid.
 
Here's some other web sites with some other information:
http://www.nysaes.cornell.edu/hort/faculty/reisch/bulletin/table/tabletext3.html
http://www.agri.gov.il/Horticulture/Breeding/MichaelStriemMAS.html
http://students.sivan.co.il/michaels/SeedPubs.html
 
Chris Mauchline
SE PA, zone 6
40° 5' N 75° 51'W
~650 ft elevation
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