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Genetics Books


Bill Shear wrote:

:  Most genetics texts these days are heavy on the biochemistry and fairly
:  light on classical Mendelian genetics, which is what most iris breeders
:  would be interested in.   So it would be a good idea to stick to older
:  "outdated" texts if what you want is a general intro to genetics. 

Thanks.  Sometimes I feel rather "outdated" myself....

:  I'd
:  suggest looking into any fairly voluminous Introductory Biology text first,
:  for a boiled-down version of how chromosomes, etc., work.

And thanks for pointing this out.  I'd sort of taken it for granted.

:  One thing missing from most texts but important to irisarians is tetraploid
:  genetics.  World of Irises has a good account of it, as well as an intro to
:  genetics in general, with iris examples.

For the more advanced, there's usually at least a passing mention in texts on
genetic statistics.  Most examples are diploids, of course, but once you master
the basics it's not hard to adapt the principles to tetraploids.

:  I suspect a lot of breeders get along very well with a minimum of knowledge
:  about genetics--after all, the old-timers who established the ancient
:  breeds of cattle, sheep and hogs as well as originated wheat and maize
:  hadn't a clue.  They simply used their eyes and other senses and selected
:  offspring with the traits they wanted.

Right!  There's a great deal of fun to be had with any of the fertile families. 

:  Somewhere I
:  read that Ray Schreiner boils down more than 10,000 seedlings to 15 or so
:  that have the potential for introduction.  Seems as if the creative process
:  here comes in the selection, perhaps more so than in the choice of
:  parents.......

I think both are essential.  There are advantages in growing large quantities of
seedlings.  I produced thousands of seedlings before selecting my first
introduction, and learned a great deal in the process.  Including the fact that
the choice of parents can improve the odds -- but it can NOT substitute for
well-thought-out selection among the resultant seedlings.

For example, in 1986 I made dozens of crosses between tetraploid RCs and
halfbreds. One of those crosses (BALLALAIKA MUSIC X SUNRISE IN GLORY) produced
CLASSIC ELEGANCE, DARINGLY DIFFERENT, and GENUINE GEMSTONES.  One (PERSIAN PANSY
X ROSE OF SHARON)  produced DOUG GOODNIGHT and another (PERSIAN PANSY X KOKO
KNOLL) produced INSCRUTABLE.  But many others produced nothing worthy of
introduction.   The lesson I learned?   BALLALAIKA MUSIC produces a much wider
variety of color/pattern combinations than PERSIAN PANSY.  You might be able to
spot a clue to that by analyzing the pedigrees of my introductions -- but you
couldn't miss it on a stroll through the seedling patch.   

To continue the sage, in 1989 and 1990 I made use of what I'd learned from the
maiden bloom of the 1986 seedling crop and made more 3/4-bred crosses with the
seedling later introduced as BALLALAIKA MUSIC and its pod parent, a seedling I
subsequently introduced as WERCKMEISTER'S BEAUTY.  The result:   THINGS TO COME,
four 1997 introductions, and several more on track for 1998.  I've continued to
experiment with other tetraploid arils, of course, but  BALLALAIKA MUSIC and
WERCKMEISTER'S BEAUTY remain the most reliable.  

Another hybridizer, looking at my pedigrees or examining my seedling patch,
might come to one of two conclusions:

1.	 BALLALAIKA MUSIC and WERCKMEISTER'S BEAUTY are great parents, I'm going
to try them with other halfbreds.  (A good strategy for someone wanting to get
something good from a limited number of seedlings.

2. 	 This type of cross looks interesting, but there's no point in
duplicating what Sharon has already done.  (A good strategy for someone with
resources to grow lots of seedlings because it could lead to something quite
different.)

Please note that neither is right or wrong.  Both are effective.  Just
different.

BTW, I've run into the 1 in 1000 rule of thumb many times -- always quoted as
applying to experienced hybridizers of TBs, not beginners.  The corresponding
rule for arilbreds is 1 in 50 to 1 in 100.  That's one reason I encourage people
to experiment with them.

I like to run these stats AFTER I've finished evaluating the seedlings produced
in a given year., to see how I'm doing compared to the experts without letting
the numbers influence my selections.  For the first five years, I averaged about
1 in 1000 -- all arilbreds, so my effectiveness rate was about 5 to 10% of that
of the experienced hybridizers.  After ten years, I broke the "magic" 1 in 100
mark.  And have ranged between 1in 50 and 1 in 100 since then.  I really don't
expect to break the 1 in 50 mark.  If I ever do, I'll certainly take a long,
hard look at the selection process.  

Sharon McAllister (73372.1745@compuserve.com)
Long-winded lunch-break -- sorry 'bout that!





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