An investigation of the susceptibility of Arabidopsis thaliana to isolates of two species of Verticillium

Eight isolates of Verticillium longisporum and seven of Verticillium dahliae were examined for their pathogenicity to Arabidopsis thaliana. Two-week-old seedlings of two A. thaliana ecotypes were inoculated with conidial suspensions (1.6 x 10(4) conidia/ml) and maintained in sterile conditions on microtitre plates for 25 days. The seedlings were assessed daily for flowering time, height at flowering and mortality. From this data the proportion of plants flowering was calculated and the susceptibility of each ecotype to individual isolate was quantified. The A. thaliana ecotypes were inoculated by several isolates of V. dahliae and V. longisporum with the disease symptoms observed being similar to those characteristic of Verticillium-infected Brassica napus. Responses to Verticillium isolates varied and for both ecotypes significant differences (P less than or equal to 0.05) were recorded in days to flowering between the V. longisporum isolates VD6 and VD12 and the V. dahliae isolate INRA617 and all other isolates. There were no other significant effects correlated with isolate origin or Verticillium species.