The diversity of races and prevalence of pathogenic populations of Fusarium oxysporum f. sp. dianthi (Fod) were surveyed in an area in southern Spain. From 54 farms, 132 isolates were collected from wilted carnation plants. Isolates were characterized by RAPD-PCR, DNA sequence analysis of the TEF1-α gene, and race-specific molecular markers. Selected isolates from RAPD groups were phenotypically evaluated by pathogenicity tests. Data analysis showed that Fod race 2 was the most frequent and prevalent race in the study area, followed by race 1/8. Moreover, phylogenetic analyses showed similar results, which were different to those of the race-specific PCR assays. It was concluded that (i) seven isolates were not classified in groups where Fod testers were clustered; even they showed different results when race-specific markers were used, (ii) ten isolates with retarded race 1 or race 8 specific band were characterized as F. proliferatum by TEF1-α gene sequencing and clustered into an outgroup, and (iii) six isolates failed to generate an amplification signal using race-specific markers. Furthermore, three of them were grouped close to race 2 tester according to the phylogenetic analyses, showing the same differential pathogenicity as race 2. This may indicate a Fod race 2 subgroup in this region. 1. Introduction Fusarium oxysporum Schlechtend. Emend. W. C. Snyder & H. N. Hans is a species complex of morphologically similar fungi with multiple phylogenetic origins that fall into three well-supported clades [1]. Pathogenic isolates of F. oxysporum often display a high degree of host specificity and can be subdivided into formae speciales on the basis of the plant species affected. 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 [2–5]. In 2009, Andalusia accounted for 55.4% of the total carnations produced in Spain, and 62.1% of this was from the province of Cádiz [6], which is the greatest producer in Europe [7]. In this area, Fusarium wilt disease appeared five years after the introduction of the first carnation plants in 1975. Since then, it has been reported continuously [8]. Despite this, exhaustive studies on race diversity and pattern of Fod distribution in this area are lacking [5]. Fod can be distinguished into physiological races on the basis of the capacity of the pathogen to attack differential carnation cultivars. To date, ten races have been described worldwide [5].
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