Clonal breakdown

John Bryan
Tue, 21 Nov 2006 13:19:18 PST
Dear All:

Hybrid vigor, while evident in plants raised from seed, does not last
for ever if continued asexual reproduction of a plant is continued over
many years. The classic example perhaps is to be found in the strawberry
Royal Sovereign, which  just failed after many years. At one time it was
far ahead of other cultivars, but then lost many of the qualities for
which it was renowned. To my knowledge such loss of desired qualities
were simply lost due to the continued asexual propagation. Just what
happens when such does take place I do not know, but such has been
refereed to as Clonal Breakdown. Possibly the desired arrangement and
composition of the cells in the plant(s)  was changed.

John Lonsdale asked how TC fix this. Again a definitive answer, to my
knowledge, as not been determined, but it does work. Perhaps this method
of propagation is taking advantage of cells that are, for want of a
better explanation, stronger and closer to the original cells of the
first crosses and better replicas of cells carrying the desired

I should have mentioned the plants of Enchantment did not show any
visible signs of virus, to all intents and purposes the plants appeared
to be the same, except for size of flowers and bud count. 

Here it must be stated, those plants used for asexual propagation, were
selected in the field, the strongest, those with good flower size and
bud count were those selected and these plants showed no color variation
in the foliage at all. Selecting those plants that are the most vigorous
is an ongoing practice of good growers. When growing many hundreds of
Dahlias, I used to tag those tubers for propagation in the field and
they were lifted first prior to the lifting of others.

John Londsale asks if reduced flower size and count are not classic
signs of viral infection, perhaps they are, but are not such accompanied
by other signs as well, such as changes in the foliage? Does this mean
such changes as clonal breakdown do not exist? When examined in the 60's
for virus, using the techniques available at that time, no virus was

Rodger Whitlock almost choked on his bagel, when he read my comments
regarding growers in the Netherlands, if you have found such poor
practices s you describe, I hope you have reported such to all
authorities who could challenge the practices and do something about it.
Is this perhaps a reason why such strict regulations are now in place
with importation of plants from overseas and which are decried by so
many? Perhaps the USDA are correct! In any profession there are rogues,
but firms such as Hoog and Dix, to mention but one, strive to maintain
the highest standards in nomenclature and health of the products they
sell. To label all growers as being, in effect, dishonest is not only
untrue but, in my opinion a libelous statement. such as Dahlias loaded
with nematodes. To which grower(s) are you referring?  Have you reported
them to authorities? If not, why not? As to the selling of wild selected
bulbs, I presume you are aware of the rule governing such and these
rules are and have been imposed by the authorities in the Netherlands.

Alani Davis asked how can one know if it is clonal breakdown and not
environmental or pathanogenic? I do not know, but the term clonal
breakdown was the term we used, other factors may well have played a
part, but let us not blame virus for all such occurrences, especially
after tests were made to see if virus was present. But as I mentioned,
this was way back in the 60's and more recent procedures might be able
to answer this question.

The posting of Jim McKenney was interesting. I had not heard the term
Clonal Drift before, but obviously this must be the same. jim, as
mentioned above, steps were taken to keep the product within the
expectations of the consumer. this is why that, during the last years I
was with Oregon Bulb Farms, we were relying on 'strains' as such, being
seed of crosses between established clones as were the seed parents, had
vigor and the variation in height, color, size and number of flowers
were between very narrow limits. Black Dragon Strain took the place of
the clone Black Dragon, and Golden Splendor Strain took the place of the
clone of the same name, etc.  Jim, could you explain somatic mutations? 
How do such differ from other mutations/ 
Cheers and Happy Thanksgiving to all I hope your turkeys are tasty, and
good eating and would there be clonal breakdown in such birds brought
about by inbreeding?

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