Control of Erwinia amylovora Growth by Moringa oleifera Leaf Extracts: In Vitro and in Planta Effects

Abstract

Erwinia amylovora (EA) is a phytopathogenic bacterium, the causative agent of bacterial fire blight, a disease that affects Rosaceaes. In order to replace antibiotics and copper, the antimicrobial activity of three extracts of Moringa oleifera Lam., methanolic (MeOH-MOE), hydroalcoholic (HA-MOE) and hydroalcoholic with maltodextrins (HAMD-MOE), was tested on eleven strains of EA isolated from apple trees by the Emilia-Romagna Phytosanitary Department. MIC and MBC have been evaluated; biofilm formation, swarming motility and amylovoran production were performed with the crystalviolet, soft-agar assay and the amylovoran method. All extracts demonstrated bacteriostatic activity at a concentration of 1 mg/mL, resulting in a 80% reduction in biofilm formation. HAMD-MOE, MeOH-MOE and HA-MOE caused an inhibition of motility of 60%, 65% and 30% after 6 days and a decrease in amylovoran synthesis of 84%, 63% and 93%, respectively. In planta results showed how the compounds were able to inhibit EA virulence on apple trees, mainly if they were applied as a preventive treatment, although the treatment showed a significant reduction in fire blight symptoms progression. The antibacterial activity of the extracts is mainly due to the high concentration of polyphenolic compounds detected in the extracts that was able to alter the permeability of bacterial membrane, resulting in slowing the synthesis of ATP and consequently of all ATP-dependent functions, such as motility and less selectivity towards harmful compounds, which can, thus, enter the cytoplasm and inhibit enzymes involved in replication and quorum sensing. The efficacy, eco-compatibility and low cost make such extracts a potential tool for the control of bacterial fire blight.

Valorization of Quercus suber L. Bark as a Source of Phytochemicals with Antimicrobial Activity against Apple Tree Diseases

“…Regarding antibacterial activity, the inhibition results against E. amylovora would be comparable to those obtained by Fontana et al [71] for the hydroethanolic, methanolic, and maltodextrin-conjugated extracts of Moringa oleifera Lam. leaves, with MIC values of 1000 µg•mL −1 ; and with those obtained for hydromethanolic extracts of P. granatum fruits [72], of flowers or leaves of Hibiscus syriacus L. [73], and of flowers or leaves of Limonium binervosum (G.E.Sm.)…”

Genomic Analysis Unveils the Pervasiveness and Diversity of Prophages Infecting Erwinia Species

“…In this study, we analyzed the occurrence and diversity of prophage-like sequences in 221 publicly available Erwinia genome assemblies. Over the years, there has been an increasing number of high-quality Erwinia genome assemblies deposited in public databases, reflecting the growth of interest in genomic characterization of this genus due to its relevance to crop production [ 35 , 36 ]. Many Erwinia species are associated with plant disease [ 37 ], to which prophages could contribute relevant genetic features such as virulence genes and superinfection exclusion [ 38 ], modulating pathogen aggressiveness.…”

Quorum‐quenching enzymes: Promising bioresources and their opportunities and challenges as alternative bacteriostatic agents in food industry

“…There are also significant risks for agriculture, because AHLs‐producing strains account for up to around 20% of the culturable bacteria in rhizospheric environments, with important contributions to plant health (Helman & Chernin, 2015). Although some biocontrol bacteria driven by AHLs can antagonize plant pathogens such as Fusarium oxysporum and Aspergillus flavus in root systems, plant‐pathogenic soil bacteria are also dependent on AHL‐mediated QS to evoke virulence factors that cause severe plant diseases including wilt (Li et al., 2020), soft rot (Liu et al., 2022), fire blight (Fontana et al., 2022), and canker (Sena‐Velez et al., 2020). In this process, the QS‐regulated virulence factors such as chitinase, cellulase, and pectinase can play an important role by broking fruit and vegetable cells.…”