Abstract
The performance of seven linear crop-water production functions was evaluated for wheat (Triticum aestivum L.) in Paraná State, Brazil. Regression parameters for relationships between crop yield and water stress index were obtained by linear regression using data from field experiments conducted over three years. Three seasonal and two growth-stage functions showed significant correlations and similar performance for predicting wheat yield. Those functions were considered appropriate for use in further studies on assessments of risk of water deficit, and crop response to irrigation in the region.