The Effect of Verticillium Infection in Runner Plant Propagation Nurseries on Resistant and Susceptible Strawberry Genotypes

Abstract

Mother plants from strawberry (Fragaria ×ananassa Duch.) genotypes susceptible to and resistant to verticillium (Verticillium dahliae Kleb.) were inoculated with this pathogen in a high elevation nursery. The infection rate for mother plants was 77.3% ± 7.5% and 80.7% ± 5.4% for resistant and susceptible genotypes, respectively. Conversely, the percentage of runner plants identified as infected by postharvest petiole assay that were produced by these inoculated mother plants differed significantly (P < 0.01) between sets of genotypes, 25.1% ± 3.7% and 59.8% ± 5.3% for resistant and susceptible genotypes, respectively. The percentage of runner plants from inoculated mothers that eventually collapsed in the fruit production field was larger than the percentage identified as infected by petiole assay for susceptible genotypes (68.9% ± 4.1%), and substantially less than the pre-plant infected fraction for resistant genotypes (3.5% ± 1.4%). Yield for runner plants from inoculated mothers was reduced by 73% to 75% for susceptible genotypes, and by 7% to 15% for resistant genotypes. The percentage of runner plants identified as infected in the nursery was correlated with the percentage of plants that collapsed in the fruiting field (r = 0.91, P < 0.01) and with yield in infested plots (r = -0.79, P < 0.01). Most of the effect of this disease was expressed as plant collapse, but the presence of yield reductions larger than the rate of plant collapse demonstrated substantial sub-lethal effects as well.