Chimeras
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- Subject: Chimeras
- From: B* M*
- Date: Wed, 28 Feb 2001 10:58:15 -0500
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Hi Everybody,
Some may be
wondering about the terms sectorial, mericlinal, and periclinal in reference to
types of chimeras in Hosta. I've prepared a diagram which I hope explains
it well enough. In a sectorial chimera, a section of mutated tissue runs through
the L1 and L2 layers as if there was no boundary. In a mericlinal chimera, the
new tissue is restricted to one layer or the other, so you get part of an edge
or part of a center. A periclinal chimera is the
most stable by far with a complete edge or center.
I've grown
quite a few hosta seedlings over the last few years so may be able to help with
Joe's questions. What I've seen is about 0 to 1.0% of seedlings from
non-streaked parents showing sectorial or mericlinal chimeras, with the
percentage varying from one batch of seed to the next. These are very
unstable and few persist or convert to periclinals. Rarely will one appear as a
periclinal or one of the others convert. Also rarely one will appear as a
streaked sport.
I don't know
what streaked plants are, and I'm not sure if anyone really understands them.
What is clear is that they do not follow the rules about the other types of
chimeras. Their offspring are also streaked in large percentages and these
streaked offspring convert to periclinal chimeras with varying frequency. What
separates them in appearance is bands of tissue in which the two different
colors are mixed together, like mixed jellybeans. I have found the presence of
this mixed tissue to be a reliable predictor of streaked progeny. Some say
the percentages of all-green, all-white, and mixed tissue are
reflected in the seedlings, but I haven't watched for this myself. In past
issues of the Journal, I remember Kevin Vaughn, Herb Benedict, Jim Wilkins, and
Ed Elslager commenting on this.
I have a question
for all------ Does the phenomenon of streaking as we know it occur in any other
genus? I have seen similar patterns, but do these plants yield streaked
offspring?
.......Bill Meyer |
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