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

Abstract

<jats:p>Eighteen commercial cultivars of carnation were inoculated with eight isolates of <jats:italic>F. oxysporum</jats:italic> fsp. <jats:italic>dianthi</jats:italic> (<jats:italic>Fod</jats:italic>) 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 <jats:italic>Fod</jats:italic>. 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 <jats:italic>Fod</jats:italic>. 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.</jats:p>

Carnation Fusarium wilt suppression in four composts

“…Susceptible cultivars suffer severe yield losses, and considerable yield losses are also common in carnation cultivars previously described as resistant (Prados-Ligero et al 2007). The crop is mainly produced as a monoculture in greenhouses; rooted cuttings are planted in late spring (May to June) and removed after 22 to 23 months before preparation of the soil for new plantings.…”

“…The crop is mainly produced as a monoculture in greenhouses; rooted cuttings are planted in late spring (May to June) and removed after 22 to 23 months before preparation of the soil for new plantings. Consequently, populations of soilborne plant pathogens often increase to unacceptable levels (Prados-Ligero et al 2007). …”

Molecular analysis of Spanish populations of Fusarium oxysporum f. sp. dianthi demonstrates a high genetic diversity and identifies virulence groups in races 1 and 2 of the pathogen

“…Moreover, R2 isolates from Italy, all of them in the R2I race group, seem to be molecularly different from the Spanish R2I isolates, because most of them amplify the R2II-associated specific amplicons with the SCAR primers. Results of Prados-Ligero et al (2007), testing the resistance of different carnation cultivars inoculated with Italian isolates of Fod, demonstrated that different isolates of the same race (R1 or R2) caused different reactions (R or S) on the same cultivar, thus suggesting the existence of pathogenic/genetic diversity in races R1 and R2 from Italy. Our results support this hypothesis and demonstrate that genetic diversity exists at least within race 1 isolates from Italy.…”

“…Soil populations of Fod can be highly diverse, even within a single soil, and the knowledge of this diversity is essential for the choice of suitable resistant carnation cultivars in specific growing areas. In fact, recent observations have shown that considerable yield losses are becoming common in carnation cultivars previously described as resistant to fusarium wilt (Prados-Ligero et al 2007). …”

Genetic Diversity of Fusarium oxysporum f. sp. dianthi in Southern Spain

“…The forma specialis dianthi (Fod) causes Fusarium wilt of carnation (Dianthus caryophyllus L.), a disease that is responsible for severe losses in areas where this flower is grown. The pathogen is widespread in soils worldwide [2][3][4][5].…”