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RE:Hyb: Cytoplasmic inheritence was disease resistance


Variagated foliage is a good example of this. It needs a nucleaus gene plus a cytoplasmic gene. The cytoplasmic gene can come from either mother or father. I'm not sure if nucleous gene is dominant or recessive but seems to be dominat. The cytoplasmc gene is a dominant.  Usually the maternal parent is the cyoplasmic recepter but it can come from the pollen paarent. This is a very complicated situation and when my  test crosses of using green maaternal parent are complete I'll comment further.

The cytoplasm is fertilized by one pollen cell and the nucleous by another. This is the situation with all plants classified as angiosperms which are almost all  plants with seeds with an ovule. Gymnosperms is the  other classification and these are represented by coniferous trees. 

This presents intersesting questions for plants from wide croses between species. Sometimes it would be possible for either the cytoplasm or the overy to be fertilized by different parents or to be parthenogenic (reproduce without fertilization sort of a virgin birth) thus cytoplasm or nucleous could be entirely from pod parent. This may explain some strange interspecies crosses were foliage looks like  mother but flower may look interspecies or where flower looks like mother but foliage looks interspecies.

It also suggests a use of mixed pollen. Thus if trying to make  a crosss of say setosa X pseudacorous, use several differnt pseudacorous clones and mix the pollen and then daub. And vice versa. This could increase the probability of a take.

A lot of early hybridizers used mixed pollen. There very well could be some of these mixed parentage cutivars out there.

Still its clear that the cytoplasmic inheritence favours the pod parent. And not all genetic material is in the nucleous.

A point to ponder.

Chuck Chapman 

Date: Sat, 29 Jan 2005 19:04:06 -0500
From: "Neil A Mogensen" <neilm@charter.net>
Subject: [iris] HYB: disease resistance

Walter Pickett mentions in his post on Iris-photos the difference in the
seedlings in the first couple of generations in reciprocal crosses in
peanuts.

It is important to remember that not all DNA is in the nucleus, and in the
chromosomes.

There are a series of structures in the cytoplasm (those parts, collectively,
that are not inside the nuclear membrane).  Among these are the mitochondria,
made famous in human studies tracing human dispersal out of East Africa
beginning by at least 60,000 years ago.  All (or perhaps most) of all human
populations alive today are descended from that out-migration.  How do the
experts know this?  Because in the DNA found in the <mitochondria>, which are
derived ONLY from the mother, a steady rate of mutation occurs.

Using those accumulating mutations, unique for each branch of the human
population as it dispersed, it is possible to draw a family tree with the
migrations showing for all humans on earth.

Another famous use of mitochondrial DNA came up in the question of whether
"Anastasia" was in fact a survivor from Czar Nicholas' family when the
Communists executed the entire family.  Both the genuine Anastasia and I
believe Philip, husband of Elizabeth II in England, share a maternal ancestor
in common--Queen Victoria.  Did they match? No.  So Anastasia was not the
genuine article.

Why does this kind of thing work?  Simply because <everything> outside the
nucleus comes from the mother in the reproductive process.  Animal spermatazoa
and plant pollen contents come from the nucleus alone.  The paternal parent
contributes nothing to the cytoplasm of the offspring.

So there are certain functions and processes that are inherited from the
mother alone.  Do these make a difference in the offspring--occasionally yes,
but usually in no significant ways. There are significant exceptions,
however.

Genetic traits originate from within the nucleus, which is a combination of
the contributions of both parents.

The structures outside the nucleus are "housekeeping" functions--such as the
chemical factories that follow the codes on the DNA and manufacture various
proteins according to the DNA blueprint instructions.  There are others that
have to do with pigments and energy exchanges--the plastids or chloroplasts.
What happens inside those with the pigments, however, again are according to
blueprints from nuclear DNA.

One place where maternal DNA in the cytoplasmic structures has been observed
is in the first generation hybrids between arils and Eupogons (pure
"true-bearded"--which is what Eupogon means-- European diploids and the
tetraploids of the AMAS sort).  Hybrids using the Eupogons as maternal
parents, I believe it was observed by C. G. White, tended to show a
predominance of bearded ancestry traits.  Those with aril maternal ancestry
were the reverse.  All of the famous diploid hybrids such as William Mohr, or
C. G. White's OYEZ and others of similar origin have the oncocyclus parent as
the pod parent.

There may be some aspects of growth, such as disease resistance, vigor or
other matters that are maternal in origin in our modern hybrids.

Neil Mogensen   z   7 western NC mountains


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