Abstract
A considerable amount of information on the procedure of crop breeding and characteristics of cultivars developed has been published, but very little information is available about the process of diffusion of cultivars released. We analyzed the diffusion process of 29 cultivars of soybean, adzuki bean, kidney bean and wheat cultivated in Hokkaido, northern part of Japan. The equilibrium level and the rate of acceptance of each cultivar were obtained by substituting yearly diffusion percentage into the logistic growth curve. Three patterns were found in the process of diffusion. The first pattern included eight leading varieties of the four crops which rapidly diffused immediately after release and had a high level of equilibrium (43∼98%). The second type had an intermediate level of equilibrium (20∼34%) and had a long longevity. The third type included 14 cultivars in which level of equilibrium was 5∼15% and that kept long longevity except for few cultivars. All cultivars except one had reached a rate of acceptance of 5% within 4 years after release. A significant negative relationship was observed between the years to the 5% acceptance rate and the equilibrium level. This shows that cultivars with a higher rate of acceptance just after release had a higher equilibrium level. However, there was no significant relationship between rate of acceptance and the equilibrium level. Three cultivars of soybean had a longevity of more than 30 years and four cultivars of adzuki bean, kidney bean and wheat had a longevity of more than 25 years from the acceptance.
