RESPONSE OF CARNATION CULTIVARS TO FUSARIUM-OXYSPORUM F SP DIANTHI INTHE FIELD

The response of carnation (Dianthus caryophyllus L.) cultivars to Fusa rium oxysporum f.sp. dianthi (F.o.d.) was evaluated in an artificially infested field from 1988/9 to 1991/2. Disease incidence was highly co rrelated with disease severity, indicating that disease incidence may be used to estimate the impact of F.o.d. on the host. Based on the res ults, the following stepwise procedure was developed for characterizin g the response of carnation cultivars to F.o.d. First, the general res ponse of the tested cultivar was classified as resistant or susceptibl e on the basis of disease incidence values recorded 180 days after pla nting. Empirical analysis of the data revealed that a disease incidenc e level of 75% may be taken as a reliable cut-off point for separation of cultivars into the two groups. Within each group, cultivars were t hen subjected to a more explicit classification: in the resistant grou p the records of actual disease incidence were used for classification . while in the susceptible group the linear rearrangement of the disea se progress curve was calculated according to the Gompertz function, a nd the value of the intercept was used for classification.