RE: streakies from greenies
I cannot help but throw in my two cents.
First of all, it is very possible to have nuclear genetic control of
variegation. These are NOT chimerae. However, I have not seen this (yet)
in hostas. Kevin Vaughn worked with Snow Flake --- see AHJ #11 (or was it
#13?). In any case, the speckled variegation is NOT the medio (central) or
marginal types that are generally selected for by hosta breeders.
Second, the preferred medio (central) and marginal types ARE chimerae. They
don't breed true.
Third, the L1 & L2 nomenclature is nothing more than a botanist's
convenience. It is a system that adequately explains observed phenomena.
Don't get confused trying to make the L# convention into a cause-and-effect
relationship --- it is not, and was never, intended to be causal, only
Fourth, please realize that there are many interactions between genes in the
nucleus, and the biochemistry in the plastids (and mitochondria, and any
other organelles), and the genes that may (or may not) exist in these
organelles. There are many examples of protein complexes where part of the
complex is produced in the nucleus, and part is produced in the organelle.
Mutations in the nuclear DNA would inherit as nuclear genes; mutations in
the organelle (including the plastid) DNA would inherit as cytoplasmic
Fifth, in the New Age of Genetics (NAG, for short), the entire idea of a
gene has been turned upside down. It is possible (indeed likely) that what
I learned to think of as a "gene" 30 years ago may not exist. The
"beads-on-a-string" concept of genes on a chromosome may indeed explain many
phenomena very well --- but it is a very incomplete concept. DNA sequences
as genes overlap, so that the same DNA sequence may get read as different
"genes" depending on where the actual "start" begins. Inheritance of all
phenomena controlled by the various "reads" would appear to be related.
Whew! That thought still brings headaches.
Joe, Jim --- it is my understanding that the partitioning of plastids in the
cytoplasm during cell division of the zygote and embryo is a totally random
event. You need mutant plastids to be present to generate a chimera;
therefore, the highest likelihood of obtaining a chimera in a cross is to
use a chimera as a seed/pod parent, since the seed parent contributes a
higher percentage of cytoplasm (and therefore more plastids) to the zygote.
There are relatively few mutant plastids in a green plant, therefore, there
are relatively few variegated chimeral seedlings produced on a green pod
In some genera (Pelargonium, for one), the pollen DOES transmit a small
number of plastids, and pollen-transmitted plastidal inheritance has been
doucmented. But again, this has not been known to occur in hostas.
That's enough for now.
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