Hypersensitive response and acyl-homoserine lactone production of the fire blight antagonists Erwinia tasmaniensis and Erwinia billingiae.
Bottom Line: They reduced symptom formation by the fire blight pathogen on immature pears and the colonization of apple flowers.In contrast to E. billingiae, E. tasmaniensis strains induced a hypersensitive response in tobacco leaves and synthesized levan in the presence of sucrose.With consensus primers deduced from lsc as well as hrpL, hrcC and hrcR of the hrp region of E. amylovora and of related bacteria, these genes were successfully amplified from E. tasmaniensis DNA and alignment of the encoded proteins to other Erwinia species supported a role for environmental fitness of the epiphytic bacterium.
Affiliation: Max-Planck-Institut für Zellbiologie, Ladenburg and Julius Kühn Institut für Pflanzenschutz in Obst- und Weinbau, Schwabenheimer Str. 101, 69221 Dossenheim, Germany.Show MeSH
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Mentions: The levan‐positive epiphytic strains Et1/99 and Et2/99 from Australia were classified into the novel species Erwinia tasmaniensis and did not affect apple seedlings nor immature pear slices to produce symptoms resembling fire blight (Geider et al., 2006). The E. tasmaniensis strains and the recently classified epiphytic bacterium Erwinia billingiae (Mergaert et al., 1999) were tested for their antagonistic effects against E. amylovora in assays with immature pear. Pear slices, which were soaked in a suspension of E. tasmaniensis or E. billingiae cells and then inoculated with E. amylovora (500 cfu ml−1), showed absence or a significant reduction of ooze production and necrosis compared with controls with water (Fig. 1A). The E. tasmaniensis strains showed often enhanced effects in 5% sucrose solution while E. billingiae Eb660 and Eb661 were as efficient in symptom reduction when pear slices were soaked with bacteria in water. Erwinia billingiae still showed strong antagonistic effects when high levels (up to 50 000 cfu ml−1) of E. amylovora were applied. The German isolate FLA03, classified as E. tasmaniensis, weakly interfered with growth of E. amylovora.
Affiliation: Max-Planck-Institut für Zellbiologie, Ladenburg and Julius Kühn Institut für Pflanzenschutz in Obst- und Weinbau, Schwabenheimer Str. 101, 69221 Dossenheim, Germany.