Matthias,

I'd like to give a short answer focusing on the following question you posed:

Is it really the model that needs to be
adapted first, or is it actually the
genotype that shows some degree of flexibility
in adjusting to the new environmental
conditions ?

Yes, I agree that genotypes have flexibility in adjusting to new
environmental conditions, but the real genetics of the variety have not
changed from one site to the next.  Just the phenotypic expression.  The
question is whether the model and the genetic coefficients as configured in
the model, allow or provide that flexibility or phenotypic expression,
called G x E.  That is the part of modeling that we are not particularly
good at, or finished with, at the present state of crop modeling.  Examples
could be genetic differences in aluminum tolerance or somewhat lower base
temperature or heat tolerance for grain set.  That means more genetic
coefficients than we currently use in the models.  It is easy to say all
this, but it will be difficult to obtain such more detailed coefficients,
as we are short on data and on real understanding of some of those issues.

Good luck with this,
Ken Boote




At 11:30 AM 2/4/04 +0100, you wrote:
>Ken,
>
>if cultivar coefficients are not site
>or environment dependant we could perform
>following comparative study:
>
>A new wheat variety has been developed
>in Sweden under temperate maritime climate
>and terminal moraine soil conditions. To
>be able to run the CERES-Wheat model
>I would get in touch with some official
>institution which performs standarized
>breeding testing programs and ask for
>their data. Such experiments are typically
>carried out under optimum management
>conditions, provide a wealth of data and
>are thus suitable for performing the
>calibration procedure (GENCALC). I would
>re-run the calibration procedure to cover
>experimental repetitions and different seasons.
>If genetic parameters are not season specific
>I would then possibly be able to obtain
>relatively stable genetic parameters.
>They would likely differ from those stated
>in the "WINTER-EUROPE" standard set.
>
>Now, only a few hundred kilometers apart
>a Polish farmers association, located let's
>say at Lodz, got interested in the high yield
>potential feature of this new breed and asks
>me to determine how this new breed will
>possibly perform under their environmental
>conditions. Since these conditions
>are entirely different from those in Sweden
>I would make the necessary modifications in
>the soil.sol file and carefully check
>the data that must be entered in the *.whx
>file. Now, if genetic coefficients for
>the new breed are universally applicable,
>as you say, I would be able to run the
>model under Polish conditions and base
>my advise on these simulation outputs.
>
>Can we have faith in such predictions ?
>
>In case we don't, were should we start
>adjusting ?
>
>Is it really the model that needs to be
>adapted first, or is it actually the
>genotype that shows some degree of flexibility
>in adjusting to the new environmental
>conditions ?
>
>
>Matthias Langensiepen
>Modelling Plant Systems
>Institute of Crop Science
>Faculty of Agriculture and Horticulture
>Humboldt-University of Berlin
>Germany