Localization ability,latent period and wilting rate in eleven carnation cultivars with partial resistance to Fusarium wilt

Summary The latent periods, wilting rates and percentages of diseased plants were analyzed for 11 carnation cultivars after root and after stem inoculation with race 2 of Fusarium oxysporum f.sp. dianth. There was no conclusive evidence for the presence of an independent extravascular resistance mechanism, except for Lena plants in which, additional to the vascular resistance components, independent root-bound factors causing retardation of the colonization and wilting process were found. A large variation was observed in the ablity of the cultivars to localize the pathogen in the vascular tissue shortly after infection of the xylem. This ability was positively correlated with the latent period, and negatively with the wilting rate and final disease index. In resistant cultivars, secondary compartmentalization of the fungus higher up in the stem was also observed. After stem inoculation, differences among the cultivars in localization ability and wilt-retarding actors could be identified at an early stage by comparing the precentages of non-colonized plants or the percentages of plants lacking vascular discolouration.