Maclean et al. - 2002 - Rice almanac source book for the most important e

eing developed at IRRI. Similar biosafety
committees have been established in other ricegrowing
countries in Asia.
One of the principal biosafety issues is the
assessment of the movement of foreign genes by
pollen dispersal from transgenic rice to other rice
varieties and wild rice. In 1995, IRRI began
operating a greenhouse designed to prevent pollen
dispersal from transgenic plants in the early
stages of evaluation. This 320-m 2 greenhouse
enables researchers to grow and multiply
transgenic plants and to evaluate them for
resistance to insects, disease, and other stresses.
A recent study using transgenic IR72 with Xa21
in a screenhouse revealed that there was no
functional transfer of transgenes from transgenic
IR72 to nontransgenic control plants, a finding
that ensures the potential use of this technology
in improving rice germplasm.
Crop modeling to integrate
knowledge
Crop modeling enables researchers to integrate
knowledge from different disciplines in a
quantitative way. That, in turn, helps researchers
to understand the underlying processes that
determine the behavior of complex agricultural
systems. Mathematical models are representations
of systems made from mathematical equations.
Integrating and solving the equations
enable a numerical description of the system to
be produced. During the first phase of a
modeling exercise, the modeler seeks to give
names, magnitudes, and units to the component
parts of the problem. In the second phase of
modeling a problem, the processes are described
as mathematical functions. In the final phase,
“what-if” questions can be asked about the
functioning of a system and numerical answers
provided. Mathematical models that contain no
clear logical link with the basic processes governing
the relationship between the system inputs
and outputs are unlikely to contribute much of
significance to any debate concerning strategic
decisions in relation to research management.
Models at different levels of detail are
developed to meet different objectives, ranging
from a thorough understanding of an existing
system to the prediction of crop production in
untested conditions. Four types of crop production
systems can be distinguished:
1. Potential production, where production is
determined by solar radiation,
temperature, and crop and varietal
characteristics.
Transgenic greenhouse at IRRI.
International issues 43