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

The response of carnation (Dianthus caryophyllus L.) cultivars to Fusarium oxysporum f.sp. dianthi (F.o.d.) was evaluated in an artificially infested field from 1988/9 to 1991/2. Disease incidence was highly correlated with disease severity, indicating that disease incidence may be used to estimate the impact of F.o.d. on the host. Based on the results, the following stepwise procedure was developed for characterizing the response of carnation cultivars to F.o.d. First, the general response of the tested cultivar was classified as resistant or susceptible on the basis of disease incidence values recorded 180 days after planting. Empirical analysis of the data revealed that a disease incidence 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 then subjected to a more explicit classification: in the resistant group the records of actual disease incidence were used for classification. while in the susceptible group the linear rearrangement of the disease progress curve was calculated according to the Gompertz function, and the value of the intercept was used for classification.