Fusarium wilt of cyclamen: Pathogenicity and vegetative compatibility groups structure of the pathogen in Argentina

Abstract

Cyclamen persicum is a winter flowering species, cultivated as a potted ornamental. It is an economically important crop in Argentina. Fusarium wilt caused by Fusarium oxysporum f. sp. cyclaminis (Foc) is a destructive disease that limits the production of quality plants. The aims of this work were to analyze Fusarium isolates from cyclamen crops in Argentina for pathogenicity and vegetative compatibility groups (VCGs) structure. As a result of crop surveys, 64 isolates of Fusarium oxysporum were obtained from cyclamen plants with typical wilt symptoms, cultivated in 13 locations in Buenos Aires and Córdoba provinces, Argentina. Pathogenicity of all the isolates was confirmed by two different methods of inoculation. Initial symptoms usually appeared 12–15 days after inoculation for both methods. All the isolates were identified as Foc. VCGs structure was determined by the complementation of nitrate-nonutilizing (nit) mutants as a visual indicator of heterokaryon formation. All the isolates were arranged in 5 VGC groups. The largest group (VCG1) included 53 isolates (83%) obtained from all of the different production areas and most commercial crops. The other VCGs were formed by 1–4 isolates obtained from 5 commercial crops. Our results suggest the existence of a uniform population of Foc in Argentina, which is widespread in geographically separated areas, since some locations are distant approximately 700km. The distribution of members of the same VCG in distant areas would demonstrate that those pathogenic isolates have a common origin, and a close genetic relationship. Since the pathogen can be spread on seed coats and in seed debris, it's introduction in Argentina with multiplication material seems possible.