The relationship between initial population density of potato cyst nematode Globodera pallida and the yield of partially resistant potatoes

The relationship between initial population density of Globodera pallida and yield was examined in five partially resistant and one non-resistant potato genotypes in a field trial. In the previous year, the experimental area had been manipulated using resistant and non-resistant potato genotypes to give plots with a range of initial population densities. The results showed that there were differences in the yield losses sustained by the different genotypes but that these were not related to their level of resistance. The data were examined using linear (Brown, 1969) and loglinear (Oostenbrink, 1966) regression models, an exponential model (Seinhorst, 1965) and an inverse linear model. The inverse linear model was found to summarise the data as adequately as the exponential model but with one less parameter.