From: samodena@csemail.cropsci.ncsu.edu (S. A. Modena)
Newsgroups: bionet.plants
Subject: Re: plant phys use in breeding
Date: 11 Sep 92 10:02:09 GMT
Distribution: bionet
Organization: Crop Science Dept., NCSU, Raleigh, NC 27695-7620

In article <1992Sep11.090444.6842@gserv1.dl.ac.uk> ajt@rri.sari.ac.uk writes:
>In article <92810050050.MIN-LXDCa20156.bionet-news@uk.ac.daresbury> you write:
>: [...]
>: For sake of illustrative example, this is what a corn (maize) breeder
>: regards as a "quick, easy and cheap" techique:
>: 
>:      Zuber and Darrah (Univ. of Missouri/Columbia -- USDA) have made
>:      excellent progress in selection for and *against* lodging
>: [...]
>
>Perhaps you are missing the point of my interest in comparing the
>anatomy of crop varieties that differ in their succeptability to
            ^^^^^^^^^^^^^^
>lodging.  I am interested in knowing *why* the differences occur and I
>have seen from the literature many qualitative statements about
>differences in anatomy.

OK, fair enough.  Here's my counter point.  Work instead on a composite
population (I can offer some leads) which has gone through cycles of
selection both for and against lodging....and then were brought back
from either extreme by further selection using the crushing strength
technique.  (These populations I seem to recall were moved as much as
10 SDs.)

>
>I am investigating these differences quantitatively.  The knowledge
>obtained should enable us to construct a _structural_ model (cf.
>empirical model) of how alterations in the proportion of different
>tissues in the stem and the distribution of cell types affect both
>lodging and degradability.

Now study these *populations* to build your structural model.

>
>My point is that it may be more productive to identify interesting
>areas by manipulating a computer model than screening fields of plants
>hoping to find something.  The objective, of course, is to produce
>improved varieties.

I have absolutely no problem with the modelling.  But you may be proposing
to construct a "model" based on genetically disparate varieties that
are all at the endpoint of selection.  You are studying them in
"static" mode, aren't you?  Study something that is under selection
and a moving target.  Quantitative descriptology of a static genetic
target might surprise you when you attempt to apply it to a moving
target *heterogeneous* genetic materials.  

I am proposing that modelling would *possibly* be more productive if
you did the same study on germplasm composite populations *known* to 
have the genetic variation needed to 1) produce advanced inbreds for
hybrid production and 2) have potential to *change* their stalk
strength and digestibility characteristics.

>
>Think about it like the Mandlebrot set (as in fractals) which has large
>uninteresting areas but very interesting regions to zoom in on and
>investigate in detail.  The trick is finding the regions of interest.

Exactly, I've suggested indirectly, and now explicitly, a standard
high yield testing techniques (crushing strength) *and* the type of
genetic precursor materials that a breeder might find acceptable as
a starting point (region of interest).

>
>	Tony.
>--
>Dr. A.J.Travis,                       |  Tony Travis
>Rowett Research Institute,            |  JANET: <ajt@uk.ac.sari.rri>
>Greenburn Road, Bucksburn,            |  other: <ajt@rri.sari.ac.uk>
>Aberdeen, AB2 9SB. UK.                |  phone: 0224-712751

And I'll give one caveat: how do you use the term "variety?"  In U.S.
breeding jargon, a variety is a phenotypically homogeneous, but
genetically heterogeneous population.  But in causal talk, a 
"variety" might refer to a particular company's propietary phenotypically
and genetically uniform 1-way or 2-way hybrid.

Steve
---
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|     In person:  Steve Modena     AB4EL                           |
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