Pathogenicity of Race‐1 and Race‐2 Tomato Wilt Isolates of <i>Verticillium dahliae</i> from Different Geographical Origins

Abstract

Abstract Fourteen race‐1 and race‐2 isolates of Verticillium dahliae from North America, Europe and Australia were screened against the near isogenic pair of tomato cultivars Roma and Roma VF. The foliar symptoms, extent of stunting and vascular colonization were assessed. Race‐1 isolates were significantly more pathogenic on Roma which lacks the Ve resistance gene. Race‐2 isolates from N. America were more pathogenic than those from Australia. All isolates tested colonized both cultivars to some extent although the level of colonization by race‐1 isolates was significantly higher in Roma than in Roma VF. All race‐1, and the majority of race‐2, isolates caused stunting of Roma. No isolates stunted Roma VF.