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Re: Hosta Variegation

Robins (interested in this subject),

I offered to Jim Anderson to try to address some views re streaked
hostas.Understanding the mecanisms of their origin and their purpose in
the Genus Hosta remains unresolved as observed in the various posts from
many quarters. My post is not intended to resolve the questions. I am
not making the case that I am right  and someone else is wrong. I simply
will try to express some views not yet presented.

Dr. Halinar has done this to some extent. Although he is relatively new
(several years he says) in hostas, he is as current as any of us are. He
has presented some views in a post this AM for consideration. I suggest
we study them seriously along with views that anyone else presents.

Joe and I have exchanged information on this subject which I hope to
share with this group also. I refer to an article written by Dr. Michael
Marcotrigiano, Associate Professor in the Department of Plant and Soil
Sciences, University of Massachusetts, Amherst, MA 101003 entitled
"Chimeras and Variegation:Patterns of Deceit", published in HortScience,
Vol.32(5), August 1997. This comprehensive 10 page, three column per
page article reviews most known types of variegation and chimeras in
plants. They are of two general types..variegation types categorized as
cell lineage types or as noncell lineage types( after Kirk and
Tilney-Bassett. 1978). In cell lineage types, cells of one color are
clonally related, that is, each colored layer, streak or patch descends
by cell division and differentiation from  the original cell in which
the color change occurred . In the case of noncell lineage variegation,
there is no relationship between the pattern of cell division and the
pattern of colors, rather the geographic location of the cell in the
organism determines the phenotype expression. This sounds awfully
complex and it is. To get an understanding of this concept, it is
necessary to read and study the article ( several times as I have done),
and then go back and do it more times.

I have written about sports in hostas as I have learned about them in my
studies. These are still ongoing altho I am 78 years old. I am anxiuos
to find out all I can before my time runs out. So, when I found out that
Dr. Marcotrigiano was on the plant tissue culture listserver sponsored
by the University of Minnesota, I wrote a post to him, recognizing that
he was now considered a world authority on variegation and chimeras in
plants. I posed a problem to him and asked for his opinion which he
kindly gave.

I noted that his article made no reference to the Genus Hosta or
micropropagation of hostas.I pointed out to Dr Marcotrigiana that the
Genus is notoriously slow using conventional garden methods of
propagation and that commercial tissue culture propagation is
responsible for its rapid increase in popularity as a shade garden
plant. Also,  because of the high incidence of chimeral and other type
bud sports in the Genes, even more new cultivars are appearing on the
scene daily. Among them are chimeral forms that are known as streaked,
splashed, mosaic or striated types. Most appear as longitudinal
green/white, green/yellow or green, white and yellow patterns of L1 and
:L2 tissue in alternating patterns in leaves. Although somewhat
unstable, they are highly prized as "breeder pod parents" because of
their ability to produce a high percentage of variegated seedlings with
different and new characteristics.

I asked specifically if he could describe the causal  factors for these
unique morphological variants found both in the garden and in tissue
culture. He answered and  gave me permission to redirect his answers to
the tc linesever if I wished but he preferred not to do so himself. I am
assuming his permission would extend to this nise lineserver also.
Therefore his quoted words ( very slightly edited to fit the context of
this discussion) follows:

"It's difficult to say since many mutants with the same type of
variegation have different genetic mechanisms controlling the phenotype.
In general, streaked and striated leaves represent unsorted plastids
mutants where some cells have white (or yellow) plastids, some green,
and some mixed. The mixed keep sorting giving a pattern of bloches or
inherited plants the streaked plants produce some eggs which have normal
and defective proplastids and can give rise to a proportion of
variegated sedlings. If the variegated seedlings sort out to a Mendelian
ratio (e.g.3:1) , I would not expect my above explanation but rather a
nuclear gene causing plastid destruction .....(which would modify color
and patterns).

Mosaic types vs chimeras can be a matter of semantics. To me a chimera
is a mosaic where the mutant and non mutant cells coexist in the shoot
apical meristem and continue to give rise to mosaic organs"

Another paragraph discussed the need to use central or axillary
meristems to avoid adventious shoots which may arise in culture which
may be non-chimeral and thus undesrable.

So there you have some views of a world authority. In my opinion, they
correspond very closely with those of Jones(1924) described in the Hosta
Wheel Web page which readers can find at www.HostaSports.com. And they
are also  almost identical to those of Vaughn as defined in Plastid
Mutants in Hostas, in AHS Bulletin 11(1982).

So I will leave readers to look for the Marcotrigiano article,( I could
Xerox a copy of those seriously interested),   the web page article
describing Jones' early classical research on chimeras and Vaughn's
article in Bulletin 11 on plastid mutants

Jim H.

PS. If I recall, one of the types of mutants was called "snow flurry" by
Vaughn.. The photo of H.'Revolution' shows an example of the snow flurry
type variegation pattern in the mutated (non-green) tissue. I have seen
this pattern  several times. I have read that it is associated with
chloroplasts around guard cells of stomata in tissues which are
otherwize comprised largely of  cells without or with a low population
of green plastids.

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