North American Fruit Explorers mailing list at ibiblio

["Lon J. Rombough" <lonrom@hevanet.com>]

The Sloe plum is P. spinosa and there are natural diploid and tetraploid forms of it.  P. insititia and P. domestica are hexaploid (or allopolyploid or just alloploid ) species.  The ancestry of P. domestica is tetraploid P. spinosa x diploid P. cerasifera (the cherry plum) which gave a triploid offspring, which was sterile.   At some point the triploid form produced what was probably a limb sport that had double the number of chromosomes.  That limb was fertile and it's seedlings were the first P. domestica.   In fact, such hybrids were produced artificially, to get the triploids, and then treated with colchicine to produce something that is indistinguishable from P. domestica and which will cross with it.  P. insititia has a similar origin, but instead of P. spinosa x P. cerasifera, the second species was something else.  The Russians used this information to produce alloploid plums using cold hardy species like P. ussuriensis and the hybrids are cross-compatible with P. domestica in an effort to get high quality cold hardy plums.  It's very hard to cross P. domestica with most other plums because of the difference in chromosome number, but it's possible to create these sort of alloploid species using most other diploid plums.
I'll add that P. domestica probably arose several times, which is why there is so much variation in it, as there were different forms of the parents involved, such as yellow cherry plums, etc.
-Lon Rombough
Grapes, writing, consulting, my book, The Grape Grower, at http://www.bunchgrapes.com  Winner of the Garden Writers Association "Best Talent in Writing" award for 2003.
On Dec 9, 2006, at 7:58 AM, Donna &/or Kieran wrote:


On the fruit front, I think that sloes also are hexaploid, like 
domestica.  I have often wondered to myself if there wasn't some way to do a 
cross to get some of the late bloming genes of the European plums 
transferred into diploid plums.  They made crosses between tetraploid and 
diploid roses, and though the results were mostly sterile they did 
eventually get some fertility and lines of tetraploids.  The thing is, that 
with 3 copies from a European plum and one copy from a diploid plum, you'd 
get a tetraploid plant, which seems to be fine for other species in the rose 
family..... but I never heard of any tetraploid species or varieties in 
Prunus.  Have you?