Physiology and modelling of traits in crop plants: implications for genetic improvement

Crop growth models have excellent potential for evaluating genetic improvem ent, for analyzing past genetic improvement from experimental data, and for proposing plant ideotypes for target environments. Crop models used for th ese plant breeding applications should be sufficiently mechanistic that pro cesses can be investigated in a manner familiar to crop physiologists and p lant breeders. In addition, the crop models must consider a sufficient numb er of cultivar-specific traits descriptive of life cycle phases, vegetative traits, and reproductive growth attributes. In this paper, we discuss how crop models consider genetic variability within a species (cultivar variati on), how varietal characteristics can be determined from variety trial or o ther data, how crop models can be used to evaluate past genetic improvement , and how crop models can be used to hypothesize ideotypes for specific env ironments. We conclude that crop growth models can partially reproduce geno type by environment interactions when considered across broad ranges of wea ther and sites, and that crop models can be used to help plant breeders tar get cultivar improvement for specific environments. However, more physiolog ical insight into primary processes such as source-sink relationships and m orphological development will be needed for enhanced application of the mod els in breeding programmes. (C) 2001 Elsevier Science Ltd. All rights reser ved.