SOYBEAN REPRODUCTIVE DEVELOPMENT - ADAPTING A MODEL FOR EUROPEAN CULTIVARS

The objective of this study was to simulate reproductive development a nd yield potential of new soybean [Glycine max (L.) Merr.] lines that might be grown in different European locations. The SOYGRO model was a dapted to European crop conditions with respect to genetic parameters for pod set, pod growth, seed set, and seed enlargement. The structure of reproductive development in the model takes into account the hiera rchy in assimilate partitioning for pod addition, shell growth, and se ed initiation. This aspect was described in relationship with canopy p hotosynthesis, temperature, and photoperiod. A sensitivity analysis wa s conducted on yield variations with 11 parameters representing phenol ogical traits, characteristics of pod and seed development, and foliag e growth in order to identify the main genetic parameters. Field deter minations of pod numbers computed from R5 to R7 on current cultivars a nd new Lines belonging to indeterminate and determinate types showed t wo kinds of fruiting processes, which appear to be independent of grow th habit and maturity group. Based on the comparison of the dynamics o f observed pod addition for the reference cultivars, a simple procedur e was proposed to calibrate the genetic parameters for new cultivars. This new procedure allowed validation of pod production and yield and provided good agreement with field data collected in several locations in Europe.