Response of strawberry genotypes to inoculation with isolates of Verticillium dahliae differing in host origin

Eight strawberry genotypes known to differ in susceptibility to verticillium wilt were inoculated with eight isolates of Verticillium dahliae originally obtained from six different host crops: strawberry, potato, watermelon, mint, eggplant (aubergine) and cauliflower. Inoculation experiments were conducted in replicated field trials during two successive years. Known susceptible genotypes developed typical symptoms of verticillium wilt in both years. Although isolates manifested a wide range of aggressiveness, differences were significant only on the most susceptible strawberry genotype. Two isolates originating from strawberry were among the most aggressive of the eight tested, whereas the least aggressive isolate was obtained from cauliflower. Six strawberry genotypes that were regarded as resistant to verticillium wilt based on previous tests were also resistant in the present study, regardless of the isolate used. Overall, strawberry genotypes represented the largest source of variation in these experiments, with variance components approximately 10-fold greater than those associated with either isolate or the isolate x genotype interaction. The results suggest it should be possible to develop resistance to verticillium wilt in strawberry that is broadly effective against isolates of diverse host origin.