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Re: hosta-open DIGEST V1 #12

  • Subject: Re: hosta-open DIGEST V1 #12
  • From: "Bill Meyer" njhosta@hotmail.com
  • Date: Wed, 29 Oct 2003 18:49:11 -0500

Hi Joe,
       One of the things we see in TC hostas that differs from
natural-division hostas is this odd issue of changes in vigor. Another is
apparent ploidy changes and changes in disease resistance. We'll skip the
latter ones for now, but my point is that there seem to be mutations that
are common in tissue culture but rare in natural division. Ben suggests
(correct me if I'm wrong) that TC batches that grow extremely slowly could
be the result of poor hormone balances impacting the health of the plant in
a way that interferes with their normal processes and therefore growth like
a malnourished puppy. This could be the case much of the time, but wouldn't
such effects wear off in a season or two and the plant resume normal growth
thereafter? The growth in these TC batches seems permanently impaired. Some
of the TC 'Great Expectations' are a good example. Even after 3-5 years
(assuming the plant survives), growth never seems to return to "normal". I
saw one batch that after two seasons had yet to make a leaf the size of a
business card. To me, this suggests a mutation has occurred. Unfortunately
in the most extreme cases like that one, it may prove impossible to test
whether this trait is passed on because they may never reach blooming size.
Then there are those TC batches said to be stronger and more vigorous than
their source material. I suppose this could be a result of a ploidy change,
but we're back to the same point with that.
       What I'm thinking here with this is that there are some types of
mutations that are more likely to occur with exposure to auxins and
cytokinins in the TC process. That are triggered more easily in that
environment but rarely in the outdoor environment. I'm not sure it's safe to
compare hostas to other plants in TC because of the much higher frequency
and variety of changes in hostas compared to other genera.
                                                     ........Bill Meyer

> Bill:
> >Treating with above-normal levels of plant hormones does seem to
> >clearly cause a number of mutations in hosta in tissue culture labs.
> High levels of hormones in TC doesn't cause mutations in other plants,
> so it is unreasonable to assume they cause mutations in hosta.  The
> "mutations" we see in hostas is more likely due to transposable
> elements and it's not all that difficult to pick them up without doing
> TC or using high levels of hormones.  Whether or not these are true
> mutations as we normally think of mutations is an interesting debate
> in semantics.  I've made some crosses using Francee sports and didn't
> detect any difference from regular Francee, but the sample population
> was too small to have any significent meaning.  In some hostas you can
> pick up small variations that seem to be fairly stable.  The question
> is how do these variations behave genetically when compared to the
> standard for that cultivar.  I've been trying to make some crosses
> along these lines, but the problem I'm having right now is that hostas
> that seem to produce the most variants are also very infertile.
> An example of how to do this would be to cross the same hosta to
> Patriot and Minuteman and compare the results.  In Francee you can
> easily see two color forms, one is darker green then the other, but
> the difference isn't easily seen unless you are looking for it.
> Patriot and Minuteman are the same variation in color as in Francee,
> but the difference is more easily seen.  Francee will also produce a
> very pale green form that is stable, but appears to be a rare sport.
> The pale green form appeared to act as a typical green Francee in
> crosses, but the fertility is so limited that it's hard to come to any
> conclusion.
> You can also do this type of cross by using a good form of Great
> Expectation and the poor growing form which is easy enough to pick up
> and crossing the two forms to something else and comparing the
> progenies from the two populations.
> Joe Halinar
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