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[mauch1@aol.com]

<<

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