It is a widespread misconception that 'Thompson Seedless' grape is
triploid. I have even seen that misconception in biology textbooks.
Several university websites also say 'Thompson Seedless' grape is
triploid:
http://www.biology.arizona.edu/cell_...iosis/04q.html
http://www.bol.ucla.edu/~bredelin/RDGenes/week3.html
http://fybio.bio.usyd.edu.au/vle/L1/...ems/Unit09.htm

However, they are in error.

The University of California seedless grape review link I posted
earlier mentions that seedlessness in grapes in caused mainly by
stenospermocarpy. It does not even mention the term triploid:

Table Grape Berry Growth and Development: A Review:
http://cetulare.ucdavis.edu/pub/Grape0302.PDF

'Thompson Seedless' grape cannot be triploid (3n) because it has been
used as a parent in breeding of other seedless grape cultivars.
Triploids cannot produce viable pollen or eggs because meiosis
requires an even ploidy number such as 2n or 4n. 'Himrod' seedless
grape is a cross between 'Ontario' and 'Thompson Seedless':

Seedless grapes:
http://www.nysaes.cornell.edu/hort/f...abletext3.html

Embryo rescue would not work with 'Thompson Seedless' if it was
triploid. However, 'Thompson Seedless' has been used as both male and
female parent in embryo rescue research:

http://www.actahort.org/books/528/528_99.htm


David R. Hershey




(MMMavocado) wrote in message ...
While I have not seen an actual report of a chromosome count, it is widely
reported that 'Thompson Seedless', the best-known, historically most important
seedless grape in the US, and from which a major percentage of the fresh grape
market, virtually all raisins, and virtually all processed grapes are produced
in this country, is triploid. Is it the odd exception to stenospermocarpy, or
are such reports in error, I wonder?