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Botrytis cinerea, the causal agent of gray mold is one of the major devastating fungal pathogens that occurs in strawberry cultivation and leads to massive losses. Due to the rapid emergence of resistant strains in recent years, an ecofriendly disease management strategy needs to be developed to control this aggressive pathogen. Bacillus velezensis CE 100 exhibited strong antagonistic activity with 53.05% against B. cinerea by dual culture method. In the present study, 50% of culture filtrate supplemented into PDA medium absolutely inhibited mycelial growth of B. cinerea whereas the highest concentration (960 mg/L) of different crude extracts including ethyl acetate, chloroform, and n-butanol crude extracts of B. velezensis CE 100, strongly inhibited mycelial growth of B. cinerea with the highest inhibition of 79.26%, 70.21% and 69.59% respectively, resulting in severe damage to hyphal structures with bulging and swellings. Hence, the antifungal compound responsible was progressively separated from ethyl acetate crude extract using medium pressure liquid chromatography. The purified compound was identified as methyl hippurate by nuclear magnetic resonance and mass spectrometry. The inhibitory effect of methyl hippurate on both spore germination and mycelial growth of B. cinerea was revealed by its dose-dependent pattern. The spore germination rate was completely restricted at a concentration of 3 mg/mL of methyl hippurate whereas no mycelial growth was observed in agar medium supplemented with 4 mg/mL and 6 mg/mL of methyl hippurate by poisoned food method. Microscopic imaging revealed that the morphologies of spores were severely altered by long-time exposure to methyl hippurate at concentrations of 1 mg/mL, 2 mg/mL and 3 mg/mL and hyphae of B. cinerea were severely deformed by exposure to methyl hippurate at concentrations of 2 mg/mL, 4 mg/mL and 6 mg/mL. No significant inhibition on tomato seed germination was observed in treatments with methyl hippurate (2 mg/mL) for both 6 h and 12 h soaking period as compared to the controls. Based on these results, B. velezensis CE 100 could be considered a potential agent for development of environmentally friendly disease control strategies as a consequence of the synergetic interactions of diverse crude metabolites and methyl hippurate. [ABSTRACT FROM AUTHOR]

Here we report the discovery and identification of antibacterial substances from the secondary metabolites of a new strain Bacillus velezensis BA-26. The whole genome of B. velezensis BA-26 was sequenced. Its genome data were annotated, and four potentially unknown gene clusters and nine known secondary metabolite synthetic gene clusters were analyzed and excavated by antiSMASH software. Based on the predicted secondary metabolites from the genome of strain BA-26, the material identification of isolated and purified extracellular secondary metabolites was conducted in combination with mass spectrometry data. A total of 24 antifungal compounds were identified, namely, iturin and various fengycins. The minimum inhibitory concentration (MIC) of iturin to Botrytis cinerea was 62.50 µg·mL−1. The MICs of C14 fengycin A, C16 fengycin A and C18 fengycin A were 62.50, 31.25 and 0.49 µg·mL−1, respectively, indicating that the increase in the number of carbon atoms in side chain fatty acids of fengycin improves its biological activity. Two kinds of anti-disease fungal compounds from B. velezensis BA-26, namely, iturin and fengycin, were purified and identified; they were found to have antibacterial activities against common pathogenic fungi. Therefore, B. velezensis BA-26 may be potentially used as a biological control agent. This study enriches the genome information on B. velezensis, elucidates the active components of B. velezensis BA-26 antibacterial substances, and provides a useful reference for using strain BA-26 as a biological control agent. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1934540. [ABSTRACT FROM AUTHOR]

Summary: Many types of yeast have been studied in the last few years as potential biocontrol agents against different phytopathogenic fungi. Their ability to control plant diseases is mainly through combined modes of action. Among them, antibiosis, competition for nutrients and niches, induction of systemic resistance in plants and mycoparasitism have been the most studied. In previous work, we have established that the epiphytic yeast Pseudozyma aphidis inhibits Botrytis cinerea through induced resistance and antibiosis. Here, we demonstrate that P. aphidis adheres to B. cinerea hyphae and competes with them for nutrients. We further show that the secreted antifungal compounds activate the production of reactive oxygen species and programmed cell death in B. cinerea mycelium. Finally, P. aphidis and its secreted compounds negatively affect B. cinerea hyphae, leading to morphological alterations, including hyphal curliness, vacuolization and branching, which presumably affects the colonization ability and infectivity of B. cinerea. This study demonstrates additional modes of action for P. aphidis and its antifungal compounds against the plant pathogen B. cinerea. [ABSTRACT FROM AUTHOR]

Pseudomonas fluorescens FD6 has been shown to possess many beneficial traits involved in the biocontrol of fungal plant pathogens, such as Botrytis cinerea and Monilinia fructicola . Vfr (virulence factor regulator) a highly conserved global regulator of gram-negative bacteria, such as the human pathogen Pseudomonas aeruginosa , is required for the expression of many important virulence traits. The role of Vfr in the regulation of biocontrol traits, such as the production of antibiotics to control fungal pathogens by antagonistic bacteria, has not been elucidated. This study investigated the effect of a vfr mutant derived from P. fluorescens FD6 to better understand the regulation of some important biocontrol traits associated with the bacterium. Biochemical studies indicated that the production of the antibiotics 2,4-diacetylphloroglucinol, pyrrolnitrin and pyoluteorin, was markedly enhanced in the vfr mutant. The vfr mutation also increased biofilm production, swimming motility and the expression of exopolysaccharide-associated gene ( pelA , pslA and pslB ) transcripts, but reduced protease production. Wheat rhizosphere and root tip colonization by the vfr mutant was higher than that by the wild type at 7 and 21 days after inoculation. These findings demonstrate that Vfr modulates the expression of several key traits and the production of important antibiotics involved in the biocontrol potential of P. fluorescens FD6. [ABSTRACT FROM AUTHOR]

Some substituted trans-hydroxystilbenes derived from pterostilbene and resveratrol were tested on germination, lethal effect and respiration of the conidia of Botrytis cinerea. These biological effects were related to the electronic character, to the lipophility of the substances and to their molecular volume. The products destroy the cellular membranes and could interfere with proteins of the electron transport systems. [ABSTRACT FROM AUTHOR]