| Verticillium dahliae and V. albo-atrum are soil-borne pathogens, and the main causes of Verticillium wilt disease. They are able to attack more than 200 plant species, including economically important crops such as potato and sunflower. The cross infection of V. dahliae between potato and sunflower were not clear. In this study, 10 isolates of V. dahliae isolated from potato and 10 from sunflower infected tissues and two highly aggressive V. dahliae isolates (Vd1396-9, Vd1389-21) and one weakly aggressive V. albo-atrum isolate, were used to investigate the cross pathogenicity of V. dahliae on potato and sunflower. The isolates were tested on two potato cultivars (Kennebec, a susceptible cultivar, and Ranger Russet, a moderately resistant one), and two sunflower hybrids (IS8048, susceptible, and 6946, moderately resistant). Most V. dahliae isolated from potato were more aggressive on potato and sunflower compared with the ones isolated from sunflower. However, each group of isolates was more aggressive on their original host. Four weakly aggressive V. dahliae isolates (P47, P09 from potato; S07, S09 from sunflower) were chosen to study the effect of passing these isolates several generations through their alternative host and their host of origin on their pathogenicity. The isolates were passed through the susceptible potato and sunflower cultivars for four generations. The comparison was among the initial isolates and their 4th passed counterparts. The results showed that potato isolates exhibit gain in their pathogenicity on either potato or sunflower when passed through susceptible potato cultivar Kennebec for four generations compared to the ones from sunflower. |
