Evaluation of Susceptibility of Carnation Cultivars to Fusarium Wilt and Determination of Fusarium oxysporum fsp. dianthi Races in Southwest Spain

Abstract

Eighteen commercial cultivars of carnation were inoculated with eight isolates of F. oxysporum fsp. dianthi (Fod) from a collection of isolates obtained from diseased plants surveyed in the main growing area of Spain. Susceptible reactions were shown in most cultivars inoculated with six isolates characterized as race 2 when tested on differentials. However, cultivars Elsy and Westcristal were fully resistant to the six isolates, whereas ‘Scarlet King’ showed a variable response, suggesting genetic diversity within race 2 of Fod. In contrast, eight cultivars inoculated with three isolates of races 1 or 8 were usually resistant except for cultivars Nelson and Solar, which were fully susceptible, and ‘Elsy’, which showed resistance to only one of the isolates. Partial polygenic inheritance of resistance to race 2 determines the complexity in the host reactions. Nine cultivars used in the previous experiment were inoculated with 13 Italian isolates of a collection of races of Fod. Cultivar reactions to isolates of different races agreed with some reports but not with others, suggesting an effect of environmental conditions or inoculation method. Reactions under field conditions sometimes differed from reactions with artificial inoculation in the greenhouse and growth chamber, usually more prone to express susceptibility.