Disease Note.

Genetic Diversity of Fusarium oxysporum f. sp. dianthi in Argentina. G. Lori, Laboratorio de Fitopatologia, Fac. de Cs. Agrarias y Forestales UNLP, 60 y 119, 1900 La Plata, Buenos Aires, Argentina . S. Wolcan, and H. Alippi, CIC, Laboratorio de Fitopatologia, Fac. de Cs. Agrarias y Forestales UNLP, 60 y 119, 1900 La Plata, Buenos Aires, Argentina. Plant Dis. 80:821. Accepted for publication 17 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0821B.

This study was carried out to examine the genetic diversity of the Fusarium oxysporum (Fo) population from carnation and to identify the physiologic races of F. oxysporum Schlechtend.:Fr. f. sp. dianthi (Prill. & Delacr.) W. C. Snyder & H. N. Hans. (Fod) in Argentina. One hundred and six strains were selected from several sites in carnation-growing areas. Vegetative compatibility was demonstrated through the pairing of complementary auxolrophic nitrate-nonutilizing mutants (nit) (1). Pathogenicity of the parental isolates was tested on rooted cuttings of White Sim and Scania cultivars. The genetic complementation tests demonstrated the existence of a single vegetative compatibility group (VCG) among the Fod strains, strains causing carnation wilt. This group was found throughout the entire area under study and the majority of strains were isolated from plants with disease symptoms. Different races of Fod always constitute a distinct VCG, with the exception of VCG 0022, which comprises two races (1 and 8). For identification of Fod races, representative mutants were paired with nits of different VCGs from the collection at the Research Institute for Plant Protection (IPO-DLO), The Netherlands. The tests demonstrated that all Fod mutants belonged to VCG 0021. The finding of a single VCG indicates that the genetic diversity of this pathogen in Argentina is not wide and only Fod race 2 is present in carnation-growing areas