Articles
AN ASSAY FOR THE VIRULENCE OF ERWINIA AMYLOVORA USING MALUS TISSUE CULTURE
Article number
217_48
Pages
283 – 284
Language
Abstract
A rapid, efficient method to determine the virulence of strains of E. amylovora (Ea) on Malus ‘Novole’ has been developed.
The method utilizes in vitro micropropagated plants (plantlets) of ‘Novole’. Shoot tip cultures are propagated, rooted and inoculated in vitro.
Rooted, 1- to 3-cm long plantlets are inoculated by dipping scissors in a suspension of Ea (5 X 107 colony forming units /ml) and then cutting one or more leaves.
Fourteen days later, plantlets inoculated with Ea strain 266 (virulent on ‘Novole’) show typical fire blight symptoms including systemic necrosis and watersoaking; plantlets inoculated with Ea strain 273 (avirulent on ‘Novole’ but virulent on most other apple cvs.) show no systemic fire blight symptoms.
When 39 strains of Ea were evaluated for their virulence to ‘Novole’ there was a significant association between data obtained from in vitro assay and from inoculation of ‘Novole’ grown in the greenhouse.
Although symptomatically there was a good correlation between the in vitro and greenhouse assays, the growth of the bacteria following inoculation differed in the in vitro and greenhouse grown plant material.
Populations of both virulent and avirulent strains decreased 6 hr after inoculation of greenhouse grown ‘Novole’ plants.
Between 6 and 72 hr after inoculation the virulent strain increased by 102, whereas the avirulent strain increased very little.
In in vitro grown plantlets, there was no decline in population after inoculation; instead cells of both strains increased logistically by 104 and 102, respectively, between 0 and 96 hr after inoculation.
The in vitro assay was used to screen 143 field isolates from North America, Europe, and Egypt for virulence.
Fourteen strains from the eastern and central US, and Canada were virulent on ‘Novole’.
The method utilizes in vitro micropropagated plants (plantlets) of ‘Novole’. Shoot tip cultures are propagated, rooted and inoculated in vitro.
Rooted, 1- to 3-cm long plantlets are inoculated by dipping scissors in a suspension of Ea (5 X 107 colony forming units /ml) and then cutting one or more leaves.
Fourteen days later, plantlets inoculated with Ea strain 266 (virulent on ‘Novole’) show typical fire blight symptoms including systemic necrosis and watersoaking; plantlets inoculated with Ea strain 273 (avirulent on ‘Novole’ but virulent on most other apple cvs.) show no systemic fire blight symptoms.
When 39 strains of Ea were evaluated for their virulence to ‘Novole’ there was a significant association between data obtained from in vitro assay and from inoculation of ‘Novole’ grown in the greenhouse.
Although symptomatically there was a good correlation between the in vitro and greenhouse assays, the growth of the bacteria following inoculation differed in the in vitro and greenhouse grown plant material.
Populations of both virulent and avirulent strains decreased 6 hr after inoculation of greenhouse grown ‘Novole’ plants.
Between 6 and 72 hr after inoculation the virulent strain increased by 102, whereas the avirulent strain increased very little.
In in vitro grown plantlets, there was no decline in population after inoculation; instead cells of both strains increased logistically by 104 and 102, respectively, between 0 and 96 hr after inoculation.
The in vitro assay was used to screen 143 field isolates from North America, Europe, and Egypt for virulence.
Fourteen strains from the eastern and central US, and Canada were virulent on ‘Novole’.
Publication
Authors
J.L. Norelli, H.S. Aldwinckle, S.V. Beer
Keywords
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