The Three Lineages of the Diploid Hybrid Verticillium longisporum Differ in Virulence and Pathogenicity.

Verticillium longisporum is an economically important vascular pathogen of Brassicaceae crops in different parts of the world. V. longisporum is a diploid hybrid that consists of three different lineages, each of which originated from a separate hybridization event between two different sets of parental species. We used 20 isolates representing the three V. longisporum lineages and the relative V. dahliae, and performed pathogenicity tests on 11 different hosts, including artichoke, cabbage, cauliflower, cotton, eggplant, horseradish, lettuce, linseed, oilseed rape (canola), tomato, and watermelon. V. longisporum was overall more virulent on the Brassicaceae crops than V. dahliae, which was more virulent than V. longisporum across the non-Brassicaceae crops. There were differences in virulence between the three V. longisporum lineages. V. longisporum lineage A1/D1 was the most virulent lineage on oilseed rape, and V. longisporum lineage A1/D2 was the most virulent lineage on cabbage and horseradish. We also found that on the non-Brassicaceae hosts eggplant, tomato, lettuce, and watermelon, V. longisporum was more or equally virulent than V. dahliae. This suggests that V. longisporum may have a wider potential host range than currently appreciated.