Abstract:Practical relative parasitic fitness data of 24 physiological races or pathotypes of Puccinia striiformis on 192 long-term planting wheat cultivars in China were determined by using artificial inoculation plot trials, historical data analysis of cultivar resistance to different physiological races of P.striiformis, and expert assessment. Based on theses data as key parameters, a model of interactions between multi-cultivars and multi-races, named CRDM was established, which also combined with planting area of different wheat cultivars in past years. This model was programmed with Visual Basic 6.0 and could output frequency of every race in the future by year-to-year if frequency of every race was inputted in a certain year. The preliminary tested results showed that the model could predict the general trend of race occurring frequency, however the model structure was simple. The model improvement and race forecast of P.striiformis was also discussed in this paper.