Date: Sun, 04 Jan 1998 18:57:23 -0500 From: Alexander and Annick Salomon <asalomon@bigfoot.com> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg42$foo@default> Subject: Re: Sexual Reproduction of Cultivars
Carl Mazur Wrote:
>Okay, time for me jump in. I'm not a specialist in genetics, however, if
>you self a plant, like S. flava for instance, don't the seedlings of that S.
>flava x self have the same genetic makeup of the original plant? If this is
>the case wouldn't any plant selfed reproduce an exact copy of itself? I was
>always under the impression that if you created a nice cross you could self
>it to maintain its identity. If this is not the case, a red vft x a second
>of the same clone = a genetically new plant? Can someone straighten me out?
When discussing genetics one refers to the phenotype and the genotype.
The first is the expression of a certain pair of genes; the second is
the actual pair. Since we have dominant and recessive genes, the
expression of a dominant gene does not tell us which pair of genes (two
dominants or dominant/recessive) an offspring contains. I do not know
whether the red gene is dominant or recessive(probably recessive)but
lets say it is dominant and call it R. Lets say green is recessive and
call it little r.
If we cross a red vft by itself and it is actually a heterozygote Rr we
get the following offspring RR 25% red
rr 25% green
Rr 50% red
and this is only for one trait. There are many chromosomes with numerous
traits and infinite combinations are still possible by selfing a plant.
Even if you cross a homozygous recessive by itself, you are only
ensuring the expression of one particular gene. The ONLY way to get an
exact genetically identical plant of a cultivar is by asexual
reproduction i.e. cuttings, or tissue culture. Therefore a selfing of
Aku ryu would be expressed as D.musc. "Aku Ryu"x self. No sexuall
produced offspring can be called by the cultivar name.
-Alexander E. Salomon, M.D.
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