Comparative genomic and transcriptome analyses of two Pectobacterium brasiliense strains revealed distinct virulence determinants and phenotypic features.

Potato soft rot caused by Pectobacterium spp. are devastating diseases of potato which cause severe economic losses worldwide. Pectobacterium brasiliense is considered as one of the most virulent species. However, the virulence mechanisms and pathogenicity factors of this strain have not been fully elucidated. Here, through pathogenicity screening, we identified two Pectobacterium brasiliense isolates, SM and DQ, with distinct pathogenicity levels. SM exhibits higher virulence compared to DQ in inducing aerial stem rot, blackleg and tuber soft rot. Our genomic and transcriptomic analyses revealed that SM encodes strain specific genes with regard to plant cell wall degradation and express higher level of genes associated with bacterial motility and secretion systems. Our plate assays verified higher pectinase, cellulase, and protease activities, as well as fast swimming and swarming motility in SM. Importantly, a unique endoglucanase S specific to SM was identified. Expression of this cellulase in DQ greatly enhances its virulence compared to wild type strain. Our study sheds light on possible determinants causing different pathogenicity of Pectobacterium brasiliense species with close evolutionary distance and provides new insight into the direction of genome evolution in response to host variation and environmental stimuli.

Antibacterial fibers impregnated with mycosynthetized AgNPs for control of Pectobacterium carotovorum.

Using biopolymers functionalized with antibacterial agents to manufacture active packaging is a clean alternative to mitigate food losses due to postharvest plant diseases. In this study, two mycosynthetized AgNPs impregnation methodologies on cotton (cationization and in situ biochemical reduction) were used to obtain the antibacterial fibers (A-AgNPs-C and A-AgNPs-IBR), which, in addition to being characterized by SEM-EDX, XRD, were evaluated as antibacterial materials. The cotton fibers showed growth inhibition of Pectobacterium carotovorum at 48 h. The reuse tests of these cotton fibers showed that the two types of fibers could have up to three successive uses without losing their effectiveness, regardless of the impregnation method used. Is important to highlight that the retention tests indicated that the AgNPs remain attached to the A-AgNPs-C and A-AgNPs-IBR fibers after several successive washes. Finally, the mycosynthesized AgNPs were also impregnated on fique fibers (Fique-AgNPs) by cationization to obtain little antibacterial sacks. Nanostructured materials that in in vivo tests on potatoes showed only 7.8 % of affectation, while the tubers stored in the traditional sacks had an affectation of 25 %. This immobilization of AgNPs in natural fibers will allow the development of a nanobiotechnological application in the storage and transport of potatoes, after performing some additional cytotoxicity tests to guarantee its safety.

New PCR-Based Assay for the Identification of Pectobacterium carotovorum Causing Potato Soft Rot.

Soft rot on potato tuber is a destructive disease caused by pathogenic bacterial species of the genera Pectobacterium and Dickeya. Accurate identification of the causal agent is necessary to ensure adequate disease management because different species may have distinct levels of aggressiveness and host range. One of the most important potato pathogens is Pectobacterium carotovorum, a highly heterogeneous species capable of infecting multiple hosts. The complexity of this species, until recently divided into several subspecies, has made it difficult to develop precise diagnostic tests. This study proposes a PCR assay based on the new pair of primers Pcar1F/R to facilitate the identification of potato isolates of P. carotovorum according to the most recent taxonomic description of this species. The new primers were designed on a variable segment of the 16S rRNA gene and the intergenic spacer region of available DNA sequences from classical and recently established species in the genus Pectobacterium. The results of the PCR analysis of genomic DNA from 32 Pectobacterium and Dickeya strains confirmed that the Pcar1F/R primers have sufficient nucleotide differences to discriminate between P. carotovorum and other Pectobacterium species associated with damage to potato crops, with the exception of Pectobacterium versatile, which improves the specificity of the currently available primers. The proposed assay was originally developed as a conventional PCR but was later adapted to the real-time PCR format for application in combination with the existing real-time PCR test for the potato-specific pathogen Pectobacterium parmentieri. This should be useful for the routine diagnosis of potato soft rot.

Efficacy of Argentinean propolis extracts on control of potato soft rot caused by Erwinia carotovora subsp.

BACKGROUND: Erwinia carotovora subsp. cause the potato soft rot, which is a major disease in agriculture. Antibacterial agents currently applied on potato soft rot often offer a restricted control and have several disadvantages. Propolis has shown a wide range of antimicrobial activity, although its effect has not been investigated on E. carotovora subsp. In this work, we tested extracts from propolis samples of Northwest Argentina against E. carotovora subsp. RESULTS: Ethanolic propolis extracts (EPEs) from samples of Santiago del Estero province, particularly from sample 4 (EPE4), showed the highest antibacterial activity, which was associated with the highest content of flavonoids. 2',4'-Dihydroxychalcone, 2',4'-dihydroxy-3'-methoxychalcone, galangin, and pinocembrin were identified as antibacterial constituents of EPE4. 2',4'-Dihydroxychalcone showed an antibacterial activity (minimum inhibitory concentration, MIC = 0.3-1.2 µg gallic acid equivalents (GAE) mL-1 ; minimum bactericidal concentration, MBC = 0.6-4.8 µg GAE mL-1 ) lower than that of bacterimycin (MIC = 2.4-9.6 µg mL-1 ; MBC = 19.2-38.4 µg GAE mL-1 ) and streptocycline (MIC = 19.2-38.4 µg mL-1 ; MBC = 38.4-76.8 µg mL-1 ). Preventive assays on unwounded and wounded potatoes showed that their immersion in EPE4 containing 87.5 µg GAE mL-1 or streptocycline containing 40 µg mL-1 was equally effective in controlling potato soft rot, reducing the disease incidence by 64.6-67.0% (unwounded tubers) and 88.0-86.0% (wounded tubers) and the disease severity by 49.8-49.8% (unwounded tubers) and 54.5-68.5% (wounded tubers). CONCLUSIONS: Flavonoid-rich propolis extracts from Northwest Argentina efficiently reduced in vivo the incidence and severity of potato soft rot caused by E. carotovora subsp.

Bacteriophages Isolated in China for the Control of Pectobacterium carotovorum Causing Potato Soft Rot in Kenya.

Soft rot is an economically significant disease in potato and one of the major threats to sustainable potato production. This study aimed at isolating lytic bacteriophages and evaluating methods for and the efficacy of applying phages to control potato soft rot caused by Pectobacterium carotovorum. Eleven bacteriophages isolated from soil and water samples collected in Wuhan, China, were used to infect P. carotovorum host strains isolated from potato tubers showing soft rot symptoms in Nakuru county, Kenya. The efficacy of the phages in controlling soft rot disease was evaluated by applying individual phage strains or a phage cocktail on potato slices and tubers at different time points before or after inoculation with a P. carotovorum strain. The phages could lyse 20 strains of P. carotovorum, but not Pseudomonas fluorescens control strains. Among the 11 phages, Pectobacterium phage Wc5r, interestingly showed cross-activity against Pectobacterium atrosepticum and two phage-resistant P. carotovorum strains. Potato slice assays showed that the phage concentration and timing of application are crucial factors for effective soft rot control. Phage cocktail applied at a concentration of 1 × 109 plaque-forming units per milliliter before or within an hour after bacterial inoculation on potato slices, resulted in ≥ 90% reduction of soft rot symptoms. This study provides a basis for the development and application of phages to reduce the impact of potato soft rot disease.

Isolation and characterization of pectolytic bacterial pathogens infecting potatoes in Nakuru County, Kenya.

AIMS: Isolation and characterization of pectolytic bacteria associated with soft rot disease of potatoes in Nakuru, Kenya, to provide the basis for the development of disease control measures. METHODS AND RESULTS: Potato tubers showing symptoms of soft rot were collected from different farms in Molo and Mau Narok regions within Nakuru county. Isolation was done using crystal violet pectate medium (CVPM). Out of the 71 isolates that showed growth on CVPM, pathogenicity tests revealed that 36 of them had the ability to macerate tissues of potato tubers. All the isolates yielded a fragment of approximately 1500 bp after 16S rDNA amplification. Using the BIOLOG microbial identification system, 20 bacterial isolates were identified as Pectobacterium carotovorum subsp. carotovorum, 7 were Pseudomonas fluorescens B while 9 were Ps. fluorescens A. Y1/Y2 primers successfully amplified pectate lyase-encoding (pel) gene, approximately 434 bp, in all the 20 P. carotovorum species. The virulence of the isolated strains to cause disease, according to pectinolytic tests, varied with change in incubation temperature of the test samples. Pectobacterium carotovorum strains were the most virulent at 30°C while disease severity due to infection by Ps. fluorescens A strains was high at 20°C compared to the other isolates. CONCLUSION: This study reveals the identity of pectolytic bacterial species from two genera, Pectobacterium and Pseudomonas, as causative agents of potato soft rot in Nakuru, Kenya. SIGNIFICANCE AND IMPACT OF THE STUDY: Research findings from this study will aid in developing suitable risk mitigation methods for adoption by farmers to prevent losses due to soft rot.

Bacillus thuringiensis: en el manejo del agente de la pudrición blanda de la papa Erwinia carotovora / Bacillus thuringiensis control of the potato soft rot Erwinia carotovora

En Colombia el cultivo de papa es el cuarto en importancia en la economía del país, y su producción alcanza las 300 millones de toneladas aproximadamente. Erwinia carotovora es una bacteria Gram negativa, anaeróbica facultativa causante de la pudrición blanda de la papa, puede llegar a generar hasta el 100% de daño en la cosecha, lo cual ocasiona grandes pérdidas económicas. Se ha establecido que la bacteria Bacillus thuringiensis es capaz de suprimir la virulencia de E. caratovora debido a que produce N-acil-homoserina-lactonasa, una potente enzima que degrada de N-acil-homoserinolactonas, que son indispensables en el mecanismo de quorum-sensing de E. caratovora. Esta circunstancia, puede ser una alternativa importante para el control de la enfermedad de la pudrición blanda de la papa. Considerando lo anterior, en este artículo se describe el proceso que emplea la bacteria Bacillus thuringiensis para inhibir la actividad de E. caratovora.

In Colombia the potato crop is the fourth in importance in the economy of the country, its production reached 300 million tons. Erwinia carotovora is a Gram-negative bacterium, facultative anaerobic which causes the soft rotting of the potato; it can potentially generate up to 100% damage in the crop, which causes large economic losses. It has been established that the bacterium Bacillus thuringiensis is able to suppress the virulence of E. caratovora because it produces N-acyl-homoserine-lactonasa, a powerful enzyme that degrades of N-acyl-homoserinolactonas, which are indispensable in the quorum-sensing mechanism of E. caratovora. This can be an important alternative for the control of the disease of the soft rotting of the potato. Considering the above, this article describes the process used by the bacterium B. thuringiensis to inhibit the activity of E. caratovora.