Abstract
The epiphyte Pantoea agglomerans 48b/90 (Pa48b) is a promising biocontrol strain against economically important bacterial pathogens such as Erwinia amylovora. Strain Pa48b produces the broad-spectrum antibiotic 2-amino-3-(oxirane-2,3-dicarboxamido)-propanoyl-valine (APV) in a temperature-dependent manner. An APV-negative mutant still suppressed the E. amylovora population and fire blight disease symptoms in apple blossom experiments under greenhouse conditions, but was inferior to the Pa48b wild-type indicating the influence of APV in the antagonism. In plant experiments with the soybean pathogen Pseudomonas syringae pv. glycinea both, Pa48b and the APV-negative mutant, successfully suppressed the pathogen. Our results demonstrate that the P. agglomerans strain Pa48b is an efficient biocontrol organism against plant pathogens, and we prove its ability for fast colonization of plant surfaces over a wide temperature range.
Highlights
Erwinia amylovora causes fire blight on different Rosaceae such as apple and pear, and it is one of the most economically relevant bacterial plant pathogens of these hosts
Comparison with the NCBI database showed high homology to a gene cluster of unknown function in Serratia proteamaculans 568 and to the recently annotated herbicolin I operon in P. vagans C9-1, respectively (Kamber et al 2012)
The function of the genes ddaA-I was described as an unconventional nonribosomal peptide synthesis in the production of the dapdiamide antibiotic (DAP) antibiotics of P. agglomerans CU0119 (Dawlaty et al 2010)
Summary
Erwinia amylovora causes fire blight on different Rosaceae such as apple and pear, and it is one of the most economically relevant bacterial plant pathogens of these hosts. A recent study describes the production of APV in the BCO P. vagans C9-1, which produces in addition the antibiotic pantocin A. The latter is associated with the suppression of E. amylovora in planta (Ishimaru 1985; Stockwell et al 2002; Dawlaty et al 2010; Kamber et al 2012). We performed comparative plant experiments between wild-type Pa48b and an APV-negative mutant coinoculated with E. amylovora in order to evaluate their biocontrol activity. We describe in this study the production profiles of APV of two P. agglomerans strains in detail and their relevance for their biocontrol efficacy against E. amylovora and Psg in plant experiments
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