HYB: re why choose one thing over another
- To: Iris Talk List
- Subject: HYB: re why choose one thing over another
- From: C* S*
- Date: Fri, 12 May 2000 11:10:25 -0700
From: amyr@jump.net
Subject: TB: HYB: Crossing to improve vigor / branching / bud count
>> 5) Cross with best available iris (in color) with some similarity in
>> parentage.
>> This cross should return better results than 2), and be similar to
>> 3)
>Why do you think that a cross with a 'distant cousin' would be
>substantially better than a sibling cross? If a sibling and a cousin
>both show better branching, I'd think the sibling might be more
>likely to retain the 'recessive' gene that produces good flower form
>and pass it on to the next generation, than a 'distant cousin.' Yes,
>inbreeding increasing the chances of passing along two recessive
>genes that can cause weaknesses, but can also cause good things to
>happen. I'd think that a sibling cross would produce some of each,
>but that a 'distant cousin' cross might not produce the desired
>effect, since you are even less sure that it would carry the 'recessive'
>gene for the good flower form you are seeking.
>
>This is just from strict biological principles, and I have NO
>iris hybridization experience, so PLEASE feel free to correct me
>here.
>
>--Amy
Amy,
I think we agree, I'm just not good at expressing myself. When I
said a cross would be better, I mean overall. In reality we only save a few
things from a cross so as long as we get at least one iris with the traits
we want we don't care what the rest look like.
Here is my 'wild ass' theory. I believe that there are thousands of
genetic factors responsible for any single trait (form,branching,vigor etc.)
that we observe. I also believe that there are MANY different combinations
of gene factors which can express a similar trait. From this assumption then
I believe that a cross between related plants is more likely to preserve the
particular combination of genetic factors that was originally selected for.
For example, if two Iris both have good branching, but arrive at this trait
through different and possibly conflicting combinations of gene factors,
then when crossed the results will be more random than if two very
genetically similar Iris were crossed. Similarly if a major fault exists,
then all related individuals have a high probability of showing this fault
in their offspring from siblings.
When I was thinking of how to remove a bad trait, it seemed that it
would be difficult to do so with siblings that also carried a similar
combination of gene factors which would lead to the same fault being
expressed. Mr. Chapmans suggestion to use a sibling which has no sign of the
bad trait is a good one, as long as such a sibling exists. I really like his
idea of intercrossing siblings that show good quality's to try and get the
form (or other trait) shown by one of the siblings, again if you are so
lucky as to have such nice siblings :)
I know line-breeding can be dangerous, but without some 'sifting' of
the genetic combinations, it seems to be just guesswork. If you want to
predict some outcome you need parents with a known or similar genetic
background.
Chad Schroter
Los Gatos CA
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