Production Practices and Quality Assessment of Food Crops. Vol. 1

Modelling Fruit Quality 77
than in the situation of reasoned chemical control, and only five for the pest-independent
case.
In conclusion, the Catiote model showed it is worth considering an integrated
modelling framework combining ecological and agronomical concerns to compare
the effect of various protection strategies on fruit quality. Here we focused on
reasoned crop protection with the view of its possible environmental impact, roughly
indicated by the number of chemical applications. Studying Catiote raised questions
about the necessary conditions for pest control. Catiote relies on assumptions
that should be carefully examined before concrete use. The Lokta-Volterra model
belongs to the class of ecological theories of population regulation that focuses
on density-dependent factors, knowing that other classes focus on densityindependent
factors such as climate, or consider a mixture of both (Dajoz, 1974).
By using situations and models that are both speculative, we only aimed at getting
an insight into the ability of future models to meet IFP requirements.
7. CONCLUSIONS AND PROSPECTS
We presented several biological models dealing with fruit quality. It is clear that
most of the models are mainly restricted to fruit growth, focusing on dry mass,
and that research in modelling must now focus on other essential aspects of fruit
quality such as acidity, firmness, vitamin content, etc. Indeed, a lot of work has been
done by physiologists and technologists on these aspects, but the resulting knowledge
has not been integrated in ecophysiological and agronomic models.
The structure of the Catiote model presented in this chapter, shows how it could
be possible to consider an ecological approach to deal with environmental problems
additionally to fruit quality. But here also, a lot remains to be done, mainly integrating
ecophysiological, agronomic and ecological knowledge into a model able
to simulate several aspects of quality in response to cultural practices, environment,
and pest and diseases. Such an integration has been done previously by
Gutierrez and colleagues, and mainly exemplified in cotton and cassava (see
Gutierrez, 1996, for a synthesis focusing on the ecological point of view, with
numerous referenced papers). However, the agronomic aspects were not completely
considered and the quality was not the aim of their models.
We are now developing an integrated model applied to the peach (‘Alexis’ project)
which combines some of the models presented here (SWAF, SUGAR, CaShoo) to
build a model able to simulate the quality of each fruit in a peach orchard in response
to cultural practices and to the occurrence of diseases. Such a model will be objectoriented
in order to facilitate its design and its evolution. The advances in computer
power make it possible to consider simulation models much more complex than
ten years ago.
ACKNOWLEDGEMENTS
We thank G. Vercambre and G. Rigou for their advices and corrections to the
manuscript.