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The effects of silicon dioxide nanoparticles (SiO2 NPs) in two concentrations (0.10 and 0.20 gL− 1) as foliar spray and seed priming was observed on plant growth attributes, chlorophyll, carotenoid, proline, activities of defense enzymes of tomato and on bacterial pathogens i.e. Pseudomonas syringae pv. tomato (Pst), Xanthomonas campestris pv. vesicatoria (Xcv), Pectobacterium carotovorum subsp. carotovorum (Pcc) and Ralstonia solanacearum (Rs), and fungal pathogens i.e. Fusarium oxysporum f. sp. lycopersici (Fol) and Alternaria solani (As) under in vitro and greenhouse conditions. Disease suppression and increase in plant growth was dependent on concentration of NPs and mode of application. Foliar spray was more effective than seed priming in increasing plant growth, chlorophyll, carotenoid, proline and activities of defense enzymes i.e. superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) in the presence and absence of pathogens. Foliar spray of 0.20 gL− 1SiO2 NPs caused highest increase in plant growth parameters, chlorophyll, carotenoid, proline and activities of defense enzymes in tomato plants and caused maximum reduction in disease indices. In vitro tests and scanning electron microscopy revealed antimicrobial effects of SiO2 NPs with varied adverse effects on pathogens under study. Plants subjected to foliar spray with 0.20 gL− 1SiO2 NPs had more plant growth attributes, chlorophyll, carotenoid, proline and defense enzymes against pathogens under study.

Background The development of ecofriendly tools against plant diseases is an important issue in crop protection. Screening and selection process of bacterial strains antagonists of 2 pathogenic bacterial species that limit very important crops, Erwinia amylovora, the causal agent of the fire blight disease, and Pectobacterium carotovorum, the causal agent of bacterial potato soft rot, were reported. Bacterial colonies were isolated from different ecological niches, where both pathogens were found: rhizosphere of potato tubers and fruits and leaves of pear trees from the northwest region of Algeria. Direct and indirect confrontation tests against strains of E. amylovora and P. carotovorum were performed. Results Results showed a significant antagonistic activity against both phytopathogenic species, using direct confrontation method and supernatants of cultures (pS. plymuthica had a better inhibitory effect than the strains of P. fluorescens against both pathogens. In vivo results on immature pear fruits showed a significant decrease in the progression of the fire blight symptoms, with a variation in the infection index from one antagonistic strain to another between 31.3 and 50%, and slice of potato showed total inhibition of the pathogen (P. carotovorum) by the antagonistic strains of Serratia plymuthica (p Conclusion This study highlighted that the effective bacteria did not show any infection signs towards plant tissue, and considered as a potential strategy to limit the fire blight and soft rot diseases.

Potato (Solanum tuberosum L.) is a tuberous crop from the Sola-naceae family which is a source of starch and food to many in Nige-ria, however, its production is being hampered in field and storage by bacterial pathogen which causes rot of the stored tubers. To this end, the study aimed at screening potatoes from different stores within Ibadan for the evaluation and diversity of bacteria pathogens responsible for rot in potatoes. Damaged stored potato samples were collected from different locations in Ibadan for studies, these samples were isolated for bacterial pathogen and characterized bio-chemically and observed under the microscope for identification. Three genera of bacteria were observed to be responsible for potato rot in the study and they include Pectobacterium carotovorum, Pseu-domonas syringae and Ralstonia solanacearum. Of all the isolated bacteria, Pectobacterium carotovorum has the highest occurrence with a frequency of 60%, while Pseudomonas syringae has a fre-quency of 33% and Ralstonia solanacearum has a frequency of 27%. The pathogenicity of the isolates were tested and this revealed that Pectobacterium carotovorum is the most virulent with a severity score of 4.3, while Ralstonia solanacearum follows with a score of 3.3 and a score of 2.7 was recorded for Pseudomonas syringae, while the control had a score of 0. The diversity and differences shown in the isolated bacteria indicated that potato rot is a serious disease which is caused by different bacteria and need an integrated ap-proach for its control from the field of harvesting to the storage house.

Pectobacterium carotovorum is a Gram-negative plant-specific pathogen that causes severe rot of postharvest vegetables. Given the safety consideration of pesticides, we developed a peptide approach...

Many plant-encoded E3 ligases are known to be involved in plant defense. Here, we report a novel role of E3 ligase SALT- AND DROUGHT-INDUCED RING FINGER1 (SDIR1) in plant immunity. Even though SDIR1 is reasonably well-characterized, its role in biotic stress response is not known. The silencing of SDIR1 in Nicotiana benthamiana reduced the multiplication of the virulent bacterial pathogen Pseudomonas syringae pv. tabaci. The Arabidopsis sdir1 mutant is resistant to virulent pathogens, whereas SDIR1 overexpression lines are susceptible to both host and nonhost hemibiotrophic bacterial pathogens. However, sdir1 mutant and SDIR1 overexpression lines showed hypersusceptibility and resistance, respectively, against the necrotrophic pathogen Erwinia carotovora. The mutant of SDIR1 target protein, i.e., SDIR-interacting protein 1 (SDIR1P1), also showed resistance to host and nonhost pathogens. In SDIR1 overexpression plants, transcripts of NAC transcription factors were less accumulated and the levels of jasmonic acid (JA) and abscisic acid were increased. In the sdir1 mutant, JA signaling genes JAZ7 and JAZ8 were downregulated. These data suggest that SDIR1 is a susceptibility factor and its activation or overexpression enhances disease caused by P. syringae pv. tomato DC3000 in Arabidopsis. Our results show a novel role of SDIR1 in modulating plant defense gene expression and plant immunity. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Bacterial soft rot disease is one of the most important and widespread bacterial diseases that cause destructive losses to the crop in a matter of days. The disease causes severe many vegetable crops including potato. In this study, four isolates of Pectobacterium carotovorum the main causal of the soft rot disease were isolated from naturally rotted tubers. Then, the isolates were subjected to a new set of primer pairs designed to amplify the pel gene which distinguish the P. carotovorum strains. The results confirmed that four isolates belong to P. carotovorum by having the pel gene. Then, a pathogenicity test was performed on potato tubers which showed variability between the isolates in pathogenicity and diseases severity. Finally, a quantitative reverse transcriptase PCR (qRT-PCR) techniquewas used to investigate the effect of the presence of the potatoes tissues on stimulating the expression of the pathogenicity genes. The gene expression of five pathogenicity genes was studied included: polygalacturonase (Peh), pectate lyase (Pel), xylanase (Xy), protease (Prt), and cellulase (Cel). The results confirmed that the presence of potatoes tissues stimulates the expression of pathogenicity genes in both strong and weak P. carotovorum isolates.

Background Blackleg and tuber soft rot are among the most important potato diseases caused by the bacteria belonging to the genera Pectobacterium. This pathogen causes significant economic losses each year. The antagonistic activity of different bacterial cultures against this pathogen was studied. Results Six hundred eight bacterial cultures isolated from potato tubers and rhizosphere soils procured from different locations across Morocco were tested for their antagonistic activity against Pectobacterium carotovorum. Forty isolates, all originating from tubers, showed positive antagonistic activity during preliminary screening. Among the 40 isolates, 10 were found to have a symptom suppression superior to 90%. Of the 10 isolates, 9 showed clear zone in the agar medium (in vitro test), with differences between antagonist’s inhibition diameter. For the in vivo test, 8 isolates induced total suppression of soft rot on potato slices (in vivo test). The other 2 biocontrol strains (Amo-23 and Atd-2) were capable to minimize soft rot symptoms of up to 94.4 and 96.2%, respectively. Among the selected strains for in planta experiment, 6 strains (namely Ame-4, Atd-2, Atd-4, Ag-216, Al-51, and Ama-501) showed total reduction of disease symptoms. Biochemical and molecular tests identified 8 strains of Bacillus sp. and 2 strains of Pseudomonas sp. Conclusions The results of the in vivo and the greenhouse experiments indicated that the selected isolates had a greatly significant effectiveness for suppressing blackleg and soft rot symptoms. The selected isolates could, therefore, be used as a biocontrol agent against blackleg and soft rot of potato.

Bacterial rots of onion are considered from the most dangerous stored and heaped onion crop diseases that cause huge loss in bulbs. Many bacterial species can induce onion bulb rots, with predominance of Pectobacterium carotovorum and Burkholderia cepacia that were used in this study. This research was conducted as an approach for improving the potential of biopesticide from actinobacteria in controlling onion bacterial rots by mixing Streptomyces coelicolor and Streptomyces lavendulae in one treatment against both P. carotovorum and B. cepacia each separately. The highest decrease in disease incidence was recorded in the mixed treatment of S. coelicolor and S. lavendulae that was recorded as 88.8% and 86.3% in case of P. carotovorum and B. cepacia, respectively, followed by the single treatment of S. lavendulae then the single treatment of S. coelicolor. Application of S. coelicolor and S. lavendulae, singly or in mixture had significantly increased the total phenols in onion bulbs but the highest increase was recorded in the mixed application treatment that recorded as 356.1% and 353.8% in case of P. carotovorum and B. cepacia, respectively. Also, the antioxidant enzymes (POX and PPO) activity was observed to be highest in case of the mixed treatment against both P. carotovorum and B. cepacia. On the otherhand lipid peroxidation was significantly decreased in all treatments but the highest decrease percentage was detected in the mixed treatment which was 53.3% and 57.7% in case of P. carotovorum and B. cepacia, respectively. Based on their efficiency and eco-safety, S. coelicolor and S. lavendulae have been recommended to be mixed in one treatment to increase the potential of biopesticide used for controlling onion bacterial rots.

Background: Soft rot Pectobacteriaceae includes the genera Pectobacterium and Dickeya, which are important plant pathogens being responsible for diseases in a wide range of plant species, with potatoes as the main group. Both genera cause pre- and postharvest losses of potatoes, resulting in huge economic losses linked with the soft rot diseases. Materials and Methods: Organic waste was used to isolate phages, with Pectobacterium carotovorum subsp. carotovorum DSM 30170 as host. Complete genome sequencing, comparative genomics, and electron microscopy were used to characterize the phage. An adsorption assay was used to estimate adsorption rate. Twenty-three strains from the genera Pectobacterium and Dickeya were used to examine the host range of the phage. Results: Pectobacterium phage Jarilo represents a novel genus of bacteriophages within the family Autographiviridae, order Caudovirales. Jarilo possesses a double-stranded DNA genome of 40557 bp with a G+C% content of 50.08% and 50 predicted open reading frames. Gene synteny and products seem to be partly conserved between Pectobacterium phage Jarilo and Enterobacteria phage T7, but limited nucleotide similarity is found between Jarilo and other phages within the family Autographiviridae. The adsorption rate of phage Jarilo increased continuously for 1 h upon infection. Phage Jarilo was not able to infect any strains of P. carotovorum and Dickeya tested with the exception of the P. carotovorum strain used for isolation. However, phage Jarilo infected 10 of 16 Pectobacterium atrosepticum strains tested. Conclusion: We propose Pectobacterium phage Jarilo as the first member of a new genus of bacteriophages within the family Autographiviridae, order Caudovirales, displaying a broad host range within the genera of Pectobacterium.

In summer of 2016, cankers were observed on 8-year-old pear trees (Pyrus communis L.) cv. Yali grafted on the Caleriana rootstock, in a commercial orchard in Monte Castelo, SC. Eight hundred out of 1200 trees died and the rest of the orchard was eradicated. Affected plants showed cankers on trunks and twigs with exudation; the branches turned brown and slowly died. Bacterial colonies were isolated on King’s B medium from infected tissues. Pathogenicity, biochemical tests were conducted and some isolates selected for whole genome sequencing using Ion Personal Genome Machine™ (PGM™) System (ThermoFisher Scientific). PCR with Y1/Y2 and PcaF/PcaR primers, specific for Pectobacterium carotovorum and Pectobacterium carotovorum subsp. actinidiae, respectively, were also carried out. The section of inoculated apple and pear branches showed longitudinal darkening, with wilt and leaf blight. Shoots of kiwifruit Actinidia deliciosa cv. Hayward inoculated with the bacterium showed no symptoms. The bacterium was re-isolated from all symptomatic tissues, satisfying Koch’s postulates. Selected isolates were gram-negative, facultative anaerobic, rod-shaped and exhibited a strong pectolytic activity in potato and carrot disks, and showed similar biochemical profile using a BIOLOG GEN III MicroPlate. The pathogen of the symptoms observed on pear trees in Brazil show highest genome (87.1%; DDH analysis) and proteome identity (99.8%; Patric analysis) with P. carotovorum subsp. actinidiae. A product of the expected size was obtained in both specific PCR (Y1/Y2 (434 bp) and PcaF/PcaR (343 bp) primer pairs). Results from the present study clearly show that P. carotovorum subsp. actinidiae was associated with canker on pear trees in Santa Catarina, Brazil.

Recent observations of increasing incidences of potato plants showing blackleg symptoms have caused serious concern for potato growers and traders in Egypt. Potato plants showing blackleg and soft rot symptoms were sampled from main potato-growing areas in Egypt during three successive seasons. Dickeya spp., Pectobacterium carotovorum and Pectobacterium atrosepticum were successfully isolated and identified from symptomatic potato plants (tubers and stems). The identity of bacterial isolates was reviled by identification methods based on different biological principles: cultural, biochemical and molecular methods. Specific primers targeting different genomic loci were selected for molecular identification, utilizing either conventional or real-time PCR. Multiple species were isolated from some infected samples revealing complex infection, which confirm the complexity and interaction of soft rot and blackleg diseases. Given that no previous reports on Dickeya diseases in Egypt were confirmed since the recent revision of its taxonomy, the result of PCR with Dickeya spp. was furtherly confirmed using DNA sequencing assay. BLASTn analyses of 16S rDNA sequences showed similarity to several species of Dickeya, with 99% nucleotide similarity to strains of, D. chrysanthemi, D. dianthicola and D. solani, respectively. Furthermore, the most commonly identified bacterial pathogen in the tested samples was P. carotovorum followed by P. atrosepticum and Dickeya spp., while P. brasiliense was never detected in any of the collected samples confirmed by real-time PCR assay. The results of such field survey suggested to help the decision makers in Egypt to establish an action plan to face the increasing risk of potato diseases caused by Dickeya spp. for the benefit of Egyptian domestic production.

The aim of this study was to isolate soilborne AHL degrading actinobacteria that can be used as biocontrol agents against the quorum sensing mediated virulence of Pectobacterium carotovorum subsp. carotovorum BR1 in in vitro and in planta studies. Actinobacterial strains capable of N-acyl homoserine lactone (AHL) degradation, Glutamicibacter nicotianae AI5a and Rhodococcus pyridinivorans AI4 were isolated and screened using Chromobacterium violaceum CV026 as a biosensor in an AHL degradation bioassay. The effect of AHL degradation by the potential biocontrol strains was studied by a co-culture assay. Reduction in plant cell wall degrading enzymes produced by PccBR1 due to the quorum quenching activity of the potential biocontrol strains was studied using colorimetric assays. The ability of the isolates to reduce soft rot symptoms was studied in in vitro cucumber and potato maceration assays. A cucumber plant infection model was developed to study blackleg in greenhouse experiments. G. nicotianae AI5a, R. pyridinivorans AI4 and R. erythropolis CRD13.3C were able to reduce 3-oxo-C6- N-acyl homoserine lactone and production of plant cell wall degrading enzymes by PccBR1. The isolates were also able to prevent and attenuate soft rot caused by PccBR1 in vitro in potato and cucumber maceration assays. The isolates were also able to prevent blackleg in an in planta cucumber infection model. Among the three actinobacterial isolates, G. nicotianae AI5a showed best results and has immense potential as a biocontrol agent against the virulence of the quorum sensing phytopathogen PccBR1.

The noxious weed Allium triquetrum (Alliaceae) has invaded widespread areas in southern Australia, forming dense monocultures that threaten indigenous ground flora. Two soilborne biocontrol agents, the fungus Stromatinia cepivora and the bacterium Pectobacterium carotovorum subsp. carotovorum (Pcc) have previously been reported as killing A. triquetrum in gnotobiotic controlled conditions. This study aimed to find why glasshouse pot trials in complex potting media and field trials showed no effect of inoculation with either agent. Bacteria were consistently isolated from inside surface-sterilised bases and bulbs of A. triquetrum. Most bacteria from actively growing plants were closely related to Bacillus but one from dormant bulbs (RPTAtOch1) belonged to Ochrobactrum. Most bacteria reduced soft rot caused by Pcc in vitro by up to 100% when inoculated the day before Pcc. Co-cultivation with Pcc reduced its extracellular pectin lyase and polygalacturonase, which target plant cell walls. RPTAtOch1 was identified as O. quorumnocens by traditional physiological, biochemical and molecular tests, whole genome sequencing and Average Nucleotide Identity comparisons. Its draft genome consisted of 76 contigs, 70% of which were closest to isolate A44 of O. quorumnocens, which antagonises soft rotting of potato by Pcc by destroying its quorum-sensing lactones but, like RPTAtOch1, does not inhibit growth of Pcc. Also, endophytic bacteria inhibited germination of S. cepivora sclerotia and so prevented white rot. Thus, the failure in biocontrol of A. triquetrum by both S. cepivora and Pcc may be due, ironically, to biocontrol of the intended pathogens by endophytic bacteria inside the target weed.

Two lactic acid bacteria (LAB) designated J02 and J13 were recovered from fermented vegetables based on their ability to suppress soft rot disease caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) on radish. J02 and J13 were identified as Lactobacillus pentosus and Leuconostoc fallax, respectively. The ability of J02 and J13 to suppress plant diseases is highly dependent on chitosan. LAB alone has no effect and chitosan alone has only a moderate effect on disease reduction. However, J02 or J13 broth cultures plus chitosan display a strong inhibitory effect against plant pathogens and significantly reduces disease severity. LAB strains after being cultured in fish surimi (agricultural waste) and glycerol or sucrose-containing medium and mixed with chitosan, reduce three cruciferous vegetable diseases, including cabbage black spot caused by Alternaria brassicicola, black rot caused by Xanthomonas campestris pv. campestris, and soft rot caused by Pcc. Experimental trials reveal that multiple applications are more effective than a single application. In-vitro assays also reveal the J02/chitosan mixture is antagonistic against Colletotrichum higginsianum, Sclerotium rolfsii, and Fusarium oxysporum f. sp. rapae, indicating a broad-spectrum activity of LAB/chitosan. Overall, our results indicate that a synergistic combination of LAB and chitosan offers a promising approach to biocontrol.

Soft rot, a major bacterial disease affecting the production of Chinese cabbage (Brassica rapa L. ssp. pekinensis) in China, has been widely attributed to Pectobacterium carotovorum subsp. carotovorum. Outbreaks of a new disease of Chinese cabbage caused considerable economic losses in many varieties from June to July of 2018 and 2019 in Harbin, China. This new disease had symptoms similar to those of soft rot but was different from bacterial rot caused by Pcc. Plants affected by this disease showed rot at the midrib of their leaves and stumps with short hyphae. A fungal strain named DBC755 was isolated from plant samples exhibiting soft rot to determine the relevant pathogen. The pathogen had a radial colonial morphology, white hyphae, and luxuriant branches in potato dextrose agar culture medium. The isolate was identified as Pythium ultimum var. ultimum on the basis of its morphology, biological characteristics, internal transcribed spacer, β-tubulin gene and coxII gene sequence analyses. A pure fungal culture was inoculated on Chinese cabbage, and rot symptoms were consistent with those observed in the field to satisfy Koch’s postulates. The discovery and biological characteristics of P. ultimum var. ultimum causing rot in Chinese cabbage provides a deeper understanding of soft rot and has great importance for the breeding of Chinese cabbage with resistance to this disease.

This study was aimed at identification and prevalence of potato soft rot and black leg disease agent in the potato production areas of Tokat province. In March-August 2018, 67 field surveys were carried out in Central, Turhal, Zile, Pazar, Erbaa, Niksar, Artova and Basciftlik districts of Tokat. The disease incidences were 0.25%, 0.33%, 0.31%, 0.5%, 1%, and 8% in Central, Erbaa, Niksar, Pazar, Turhal, and Zile district, respectively. In Artova and Basciftlik districts, no disease was encountered. The following tests, pectolytic activity on potato, gram reaction, catalase, oxidase, growth at 37°C and 39°C, salt tolerance, hypersensitivity reaction were applied to isolates obtained from diseased plant and tuber samples. In the PCR assay, 19 isolates were produced 434 bp product with Y1/Y2 primers specific to Pectobacterium spp., and 3 isolates were produced 420 bp product with ADE1/ADE2 primers specific to Dickeya spp. The isolates resulted positive with Y1/Y2 primers weren’t produced PCR product with ECA1/ECA2 primers specific to Pectobacterium atrosepticum. According to this, 19 isolates were identified as Pectobacterium carotovorum. With this study, the causal agent of potato blackleg and soft rot disease have been identified in the potato production areas of Tokat. Further studies will be conducted to determine the species and subspecies level of the pathogens using specific primers. Bu çalışma ile, Tokat ili patates üretim alanlarında patates karabacak ve yumuşak çürüklük hastalığının bulunma oranının belirlenmesi ve etmenin tanılanması amaçlanmıştır. 2018 yılı MartAğustos ayları arasında Tokat ili Merkez, Turhal, Zile, Pazar, Erbaa, Niksar, Artova ve Başçiftlik ilçelerinde patates üretiminin yoğun olarak yapıldığı alanlarda yapılan arazi surveylerinde 67 tarla incelenmiş olup, Tokat ilinde hastalığın Merkez’de %0,25, Erbaa ilçesinde %0,33, Niksar ilçesinde %0,31, Pazar ilçesinde %0,5, Turhal ilçesinde %1 ve Zile ilçesinde %8 oranında bulunduğu belirlenmiştir. Artova ve Başçiftlik ilçelerinde ise hastalığa rastlanılmamıştır. Toplanan hastalıklı bitki ve yumru örneklerinden elde edilen izolatlara, patateste pektolitik aktivite, gram reaksiyon, katalaz, oksidaz, 37°C ve 39°C sıcaklıklarda gelişim, tuza tolerans, tütünde aşırı duyarlılık testleri uygulanmıştır. Pectobacterium spp.’ye spesifik Y1/Y2 primerleri ile 19 izolat 434 bç PCR ürünü oluşturmuştur. 3 izolat Dickeya spp.’ye spesifik ADE1/ADE2 primerleri ile 420 bç PCR ürünü oluşturmuştur. Y1/Y2 primerlerine pozitif sonuç veren izolatlar ile Pectobacterium atrosepticum’a spesifik ECA1/ECA2 primerleri ile yapılan PCR çalışmasında ise izolatlar PCR ürünü oluşturmamıştır. Buna göre 19 izolat Pectobacterium carotovorum olarak sınıflandırılmıştır. Yapılan bu çalışma ile, Tokat ilinde patates üretim alanlarında patates karabacak ve yumuşak çürüklük hastalığına sebep olan etmenler belirlenmiş olup, ileriki çalışmalarda spesifik primerler ile tür ve alttür düzeyinde etmenlerin belirlenmesi planlanmaktadır.

Bacteria from Enterobacteriaceae family (SRE) are significant problem in plant production, not only during vegetation, in the field, but also during storage and marketing of agricultural commodities. Species P. carotovorum subsp. brasiliense (Pcb) is a newly identified member of Enterobacteriaceae family. It causes soft rot of different plant species, including root vegetables. Pcb is described as a new subspecies of P. carotovorum due to differences in phenotypic and genotypic characteristic, more pronounced virulence and aggressiveness. Patohogenicity of this bacterium is based on the production of several enzymes: pectatliase, polygalacturonase, cellulase and proeteases. The aim of this study was to determine whether and at which rate Pcb isolates originating from potato plants exhibit pectolytic activity on root of different root vegetable species - carrot, radish, celery, kohlrabi and beetroot. The obtained data confirmed wide host range of the bacterium Pectobacterium carotovorum subsp. brasiliense, but pointed to significant differences in pectolytic activity on different species of root vegetables (carrot, radish, celery, kohlrabi), while on beetroot tested Pcb isolates did not exhibit pectolytic activity. Moreover, on same species of root vegetables different levels of pectolytic activity of tested Pcb isolates were recorded.

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., Escalera de Excelencia” Programme Grant/Award Number: CLU-2017-03 P.O. FEDER of Castilla y León Grant/Award Number: 14-20

Soft rot caused by Pectobacterium sp. is responsible for significant losses in vegetable production worldwide. Methods for the effective control of soft rot are limited and are primarily based on good agricultural practices. The use of bacteriophages as biocontrol agents appears to be a promising alternative to combat phytopathogens. In this study, we investigated the efficacy of lytic phages recovered from symptomatic tissues and environmental samples against soft rot caused by Pectobacterium carotovorum subsp. carotovorum. Three bacteriophage isolates, designated as vB_PcaP-A3, vB_PcaM-D1, and vB_PcaM-J3, were observed to effectively lyse P. carotovorum subsp. carotovorum. Phage vB_PcaP-A3 exhibited virion morphology similar to the members of the podovirus group, while phages vB_PcaM-D1 and vB_PcaM-J3 showed myovirus morphology based on transmission electron microscopy. The optimal multiplicity of infection (MOI) differed greatly among the three phages. All three phages survived incubations at 30°C, 40°C and 50°C and pH conditions ranging from 3.0 to 9.0, but were all inactivated at 60°C and at pH 12. Both monophage and cocktail preparations were effective in inhibiting the growth of P. carotovorum subsp. carotovorum in the in vitro challenge tests. In the semi-in planta assays, while treatment with cocktail preparations completely inhibited the development of soft rot in tissue slices, monophage treatments not only resulted in significant reduction of tissue maceration in slices, but also showed protective effect against soft rot in tubers. Overall, these results demonstrate the efficacy of phages vB_PcaP-A3, vB_PcaM-D1, and vB_PcaM-J3 for the biocontrol of soft rot caused by P. carotovorum subsp. carotovorum.

Pectobacterium and Dickeya species are the causal agents of blackleg and soft rot diseases in potatoes. The main pathogenic species identified so far on potatoes are Dickeya dianthicola, Dickeya solani, Pectobacterium atrosepticum, Pectobacterium brasiliense, Pectobacterium carotovorum, and Pectobacterium parmentieri. Ten years ago, the most prevalent Soft Rot Pectobacteriaceae in Europe were the Dickeya species, P. atrosepticum and P. carotovorum, with some variations among countries. Since then, a drastic increase in the abundance of P. brasiliense has been observed in most European countries. This shift is difficult to explain without comparing the pathogenicity of all Dickeya and Pectobacterium species. The pathogenicity of all the above-mentioned bacterial species was assessed in field trials and in vitro tuber slice trials in Switzerland. Two isolates of each species were inoculated by soaking tubers of cv. Desiree in a suspension of 105 CFU/mL, before planting in the field. For all trials, the Dickeya species were the most virulent ones, but long-term strain surveys performed in Switzerland indicate that P. brasiliense is currently the most frequent species detected. Our results show that the pathogenicity of the species is not the main factor explaining the high prevalence of P. brasiliense and P. parmentieri in the Swiss potato fields.

Biotic stress caused by pathogenic microorganisms leads to damage in crops. Tomato and carrot are among the most important vegetables cultivated worldwide. These plants are attacked by several pathogens, affecting their growth and productivity. Fourteen plant growth-promoting actinomycetes (PGPA) were screened for their in vitro biocontrol activity against Solanum lycopersicum and Daucus carota microbial phytopathogens. Their antifungal activity was evaluated against Fusarium oxysporum f. sp. radicis-lycopersici (FORL) and Rhizoctonia solani (RHS). Antibacterial activity was evaluated against Pseudomonas syringae, Pseudomonas corrugata, Pseudomonas syringae pv. actinidiae, and Pectobacterium carotovorum subsp. carotovorum. Strains that showed good in vitro results were further investigated in vitro (cell-free supernatants activity, scanning electron microscope observations of fungal inhibition). The consortium of the most active PGPA was then utilized as biocontrol agents in planta experiments on S. lycopersicum and D. carota. The Streptomyces albidoflavus H12 and Nocardiopsis aegyptica H14 strains showed the best in vitro biocontrol activities. The diffusible and volatile compounds and cell-free supernatants of these strains showed both antifungal (in vitro inhibition up to 85%, hyphal desegregation and fungicidal properties) and antibacterial activity (in vitro inhibition &gt, 25 mm and bactericidal properties). Their consortium was also able to counteract the infection symptoms of microbial phytopathogens during in planta experiments, improving plant status. The results obtained highlight the efficacy of the selected actinomycetes strains as biocontrol agents of S. lycopersicum and D. carota.

Pectobacterium spp. are a major cause of loss in vegetable and ornamental plant production. One of these species, Pectobacterium carotovorum, can cause soft rot disease on many plants, particularly potato. These diseases lead to significant economic loss and pose food security threats by reducing crop yields in the field, in transit, and during storage. The Gram-negative enterobacterium P. carotovorum WPP14 is a particularly virulent strain for which there is no available closed genome, limiting the molecular research for this important pathogen. Here, we report a high-quality complete and annotated genome sequence of P. carotovorum WPP14. The 4,892,225-bp genome was assembled with Nanopore reads and polished with Illumina reads, yielding 394× and 164× coverage, respectively. This closed genome provides a resource for research on improved detection and biology of P. carotovorum, which could translate into improved disease management.

Plant diseases are important issues in agriculture, and the development of effective and environment-friendly means of disease control is crucial and highly desired. Antimicrobial peptides (AMPs) are known as potential alternatives to chemical pesticides because of their potent broad-spectrum antimicrobial activity and because they have no risk, or have only a low risk, of developing chemical-resistant pathogens. In this study, we designed a series of amphipathic helical peptides with different spatial distributions of positive charges and found that the peptides that had a special sequence pattern “BBHBBHHBBH” (“B” for basic residue and “H” for hydrophobic residue) displayed excellent bactericidal and fungicidal activities in a wide range of economically important plant pathogens. The peptides with higher helical propensity had lower antimicrobial activity. When we modified the peptides with a long acyl chain at their N-terminus, their plant protection effect improved. Our application of the fatty acyl-modified peptides on the leaves of tomato and Arabidopsis plants lessened the infection caused by Pectobacterium carotovorum subsp. carotovorum and Botrytis cinerea. Our study provides important insights on the development of more potent novel AMPs for plant protection.

Potato blackleg is frequently observed on the production fields in the Backa region of Vojvodina province, which is one of the largest potato-growing areas in Serbia. This disease usually occurs during June and July. In July 2020, blackleg symptoms in the form of stem necrotic lesions, vascular discoloration, hollow stems, and wilting of whole plants were noted on potato cultivar VR808 on a field 28 ha in size located in Maglic village (GPS coordinates 45.349325 N, 19.542768 E). Disease incidence was estimated at 20-25%. Isolations were performed from 12 potato samples on Crystal Violet Pectate medium (CVP). Stem sections consisted of brown lesions and healthy tissue (c.10 cm) were surface sterilized with ethyl alcohol 70% (w/v) and rinsed with sterile distilled water. Small pieces of tissue were taken at the edges of stem lesions (between healthy and diseased tissue) were soaked in phosphate buffer saline for 20 min and plated using a standard procedure (Klement et al. 1990). Single colonies that formed pits after 48 hours at 26 °C were re-streaked onto Nutrient Agar (NA) where creamy white colonies with smooth surfaces were formed. A total of 30 isolates were selected and DNA isolated from the colonies was further analyzed by polymerase chain reaction (PCR) using the partial dnaX gene (DNA polymerase subunit III gamma/tau) with primer pair dnaXf/dnaXr for Pectobacterium and Dickeya species identification (Slawiak et al. 2009). A single characteristic band of 535 bp was amplified in all isolates (Slawiak et al. 2009). DNA sequence alignment showed two distinct groups of isolates (Fig.S1), which were genetically uniform within each group. Using BLASTn search, it was established that the dnaX sequence of the first group (consisting of 19 Serbian potato isolates) had 99.79% identity with NCBI-deposited Pectobacterium versatile strains 14A and 3-2 from potato from Belarus (Acc. No. CP034276 and CP024842, respectively) as well as SCC1 from Finland (Acc. No. CP021894). The remaining 11 dnaX sequences had 100% identity with Pectobacterium carotovorum subsp. carotovorum strain CFBP7081 originating from water in Spain (Acc. No. MK516961). The partial dnaX sequences of three Serbian P. versatile isolates (Pv1320, Pv1520, and Pv1620) and one P. carotovorum subsp. carotovorum (Pcc2520) were deposited in GenBank under Acc. No. MW839571, MW805306, MW839572, and MW805307, respectively. These results, indicating combined infection in the observed field, signify the first identification of P. versatile in Serbia. Multilocus sequence analysis (MLSA) performed with proA (proAF1/ proAR1) and mdh (mdh2/mdh4) genes (Ma et al. 2007; Moleleki et al. 2013) grouped three tested Serbian potato P. versatile isolates together with P. versatile strains from NCBI (Fig.S2). For both tested genes, BLASTn search revealed 100% homology with P. versatile strain SCC1 from Finland. Three Serbian P. versatile potato isolates were deposited under Acc. Nos. MZ682623-25 for proA and MZ682620-22 for mdh genes. According to the routine tests suggested for Pectobacteriaceae (Schaad et al. 2001), Serbian isolates possessed microbiological traits identical to P. versatile description (Portier et al. 2019). Pathogenicity was performed on potato cultivar VR808 with three selected P. versatile isolates (Pv1320, Pv1520, and Pv1620) in the following assays: (i) surface-sterilized tuber slices with holes in the center filled with 100 µL of bacterial suspensions (adjusted to 109 CFU mL-1) to test the isolates' ability to cause soft rot, and (ii) young, four-week old plants with developed 3rd true leaf (c. 30 cm tall) were inoculated by injecting stems with bacterial suspension adjusted to 107 - 108 CFU mL-1 at a height 5 cm above the soil line. Negative controls were treated with sterile distilled water. Inoculated plants were kept under controlled conditions (25 °C temperature and >70% relative humidity). Each assay was replicated twice. Soft rot appeared on tuber slices 24 h after inoculation. On inoculated stems, initial symptoms manifested as greasy elongated spots at inoculation sites two days after inoculation (DAI), and subsequently extended along the vascular tissue and became necrotic. Whole plant's decay was recorded in five DAI, while negative controls remained healthy. To complete Koch's postulates, bacteria were re-isolated from symptomatic potato plants and confirmed by PCR and sequencing of dnaX. This first report of P. versatile in potato indicates that blackleg currently present in Serbia is caused by a diverse bacterial population. This pathogen was first identified in genome comparison as 'Candidatus Pectobacterium maceratum' (Shirshikov et al. 2018) and was later renamed as Pectobacterium versatile sp. nov. (Portier et al. 2019). Thus far, bacterium Pectobacterium carotovorum subsp. brasiliensis has been recognized as dominant pathogen on most of the infected fields in Vojvodina province, and was recently noted on one plot subjected to a combined infection with Dickeya dianthicola (Markovic et al. 2021). Findings achieved in this study are highly relevant, as they point to the diversity in potato blackleg pathogens, likely due to the increasingly widespread distribution of imported seed potatoes.

Bacterial soft rot is one of the major destructive diseases affecting crop production worldwide. In summer 2017, soft rot of fruit and stem blight was observed on bell pepper in commercial fields in south Georgia, USA. Bacteria were isolated from infected fruits and stems, and 5 isolates (MPS05, MPS06, PF01–2, PF04–3 and PF05–3) were characterized in the study. The isolates were identified as Pectobacterium carotovorum subsp. brasiliense (Pcb) and P. aroidearum (Pa) by morphological characteristics, biochemical and physiological tests, PCR amplification using Pcb-specific primers, and phylogenetic analysis of the 16S rDNA sequences. Pathogenicity tests on bell pepper seedlings indicated that isolates MPS05 (Pcb) and PF05–3 (Pa) were aggressive, causing plant tissue discoloration, lesions on leaves and stems, plant wilt and death. Inoculation of bell pepper fruit with MPS05 and PF05–3 at different concentrations (105, 106, 107 and 108 CFU/ml) resulted in fruit tissue maceration and complete fruit rot. To our knowledge, this study is the first report of disease caused by P. carotovorum subsp. brasiliense on pepper in the United States and the first report of P. aroidearum causing disease on pepper in the world.

Saccharin is generated from probenazole (PBZ) in plants and acts as a plant defense activator. Our study of the mechanism underlying saccharin-induced systemic acquired resistance in Arabidopsis thaliana suggests an antagonistic interaction between salicylic acid (SA)- and jasmonic acid (JA)-signaling as revealed through gene expression analyses. In wild-type plants (Col-0) exposed to saccharin, there was a consistent increase in callose deposition and in expression of SA-marker genes, PR1 and PR2, which coincided with a decrease in expression of JA-marker genes such as VSP2, LOX2 and PDF1.2. Actually, pretreatment of Col-0 with saccharin or PBZ conferred resistance to Pseudomonas syringae pv. tomato DC3000, but not to Pectobacterium carotovorum subsp. carotovorum, Botrytis cinerea, or Colletotrichum higginsianum. Enhanced expression of SA- and JA-marker genes and the augmented deposition of callose were evident after a challenge with virulent DC3000 in saccharin-pretreated plants. Consistently, pretreatment of saccharin and PBZ with SA- and JA-defective mutants led to diminished resistance in NahG-transgenic and npr1 mutant plants, but not in jar1 mutant plants, suggesting that saccharin and PBZ induce resistance in A. thaliana against Pto DC3000 mainly via activation of SA-signaling, leading to suppression of JA/ET-signaling and vice versa. Collectively, an antagonism between SA- and JA-signaling conditioned by saccharin renders resistance to a specific pathogen in Arabidopsis.

Background. At present, the problem of plant colonization by bacteria pathogenic for human is of particular interest. Among the bacteria capable of polyhostality, species of the Enterobacteriaceae family, which includes both phytopathogenic and human pathogens, are of particular interest. Fruits and vegetables contaminated with such pathogens have been shown to be able to cause human intestinal infections. Being one of the ways of communication in the plantmicroorganism system, it is possible that the synthesis of indole acetic acid (IAA) by Enterobacteriaceae determines the growth rate of bacteria, contributing to more rapid colonization of the plant.Aim: comparative study of the synthesis of IAA by different types of enterobacteria.Methods. Eight types of enterobacteria were used in the study, seven of which were isolated from sick people, as well as the phytopathogen Pectobacterium carotovorum spp. carotovorum. The work was performed using microbiological and spectrophotometric research methods.Results. The ability of the synthesis of IAA by opportunistic microorganisms belonging to the Enterobacteriaceae family was studied. We found that the majority of the studied strains synthesize IAA. Studies on the effect on the synthesis of IAA, the introduction into the nutrient medium of tryptophan and its enrichment with glucose, as well as the variation of the temperature regime of the cultivation of bacteria were carried out.

Blackleg and soft rot of potato cause economic loss through reduced yield and quality. The causal agents of bacterial blackleg and soft rot of potato were identified based on biological data and sequence analyses of the 16S rDNA gene. Between 2016 and 2018, diseased potato stems and tubers were collected in Chai Prakan District, Chiang Mai Province, and Chiang Khum District, Pa Yao Province. The symptoms included black stem lesions, soft rot on tubers, wilting, break down of the stem vascular ring and foliar yellowing. Of 13 bacterial isolates, five were identified as Pectobacterium carotovorum subsp. brasiliense, four‐Dickeya dadantii, two‐Pseudomonas putida and two‐Bacillus altitudinis. Pathogenicity tests of P. carotovorum subsp. brasiliense and D. dadantii resulted in lower leaves turning yellow and wilting followed by blackleg symptoms on lower stems and maceration of tuber tissue. Symptoms caused by P. putida were yellowing and wilting of leaves. B. altitudinis caused yellowing of the lower leaves and wilting followed by drying of leaf tissue. This is a first report of these bacterial pathogens causing blackleg and soft rot of potato in Thailand.

In this study, an antagonistic yeast isolate, Wickerhamiella versatilis was considered as a promising biocontrol agent against Pectobacterium carotovorum subsp. Carotovorum (Pcc) the causal...

The integral defense responses of plants triggered by the small molecules of plant pathogens are regarded as plant immunity. The pathogen-associated molecular pattern-triggered immunity (PTI) occurs on the recognition of a pathogen by receptors on plant cell surfaces as an infection begins. During the activation of PTI, the effectiveness of a plant’s photosynthetic system may be altered. In this study, chlorophyll fluorescence was used to assay the dynamic changes of PTI. When we used flg22Pst as an elicitor, we found that the photosynthetic electron transport rate (ETR) of Arabidopsis thaliana Col-0 was significantly decreased at 2, 4, and 24 h on treatment with a PTI-intensifying protein, plant ferredoxin-like protein (PFLP). In addition, this reduction in the photosynthetic ETR was also carried out with a PTI-intensifying Bacillus amyloliquefaciens strain, PMB05, on the induction of flg22Pst. The disease resistance against bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) was still enhanced by PMB05. Interestingly, among the eight tested Bacillus species strains, the PTI triggered by HrpNPcc from P. carotovorum subsp. carotovorum exhibited an ETR that was significantly decreased by PMB05. Furthermore, this decrease was consistent with rapid H2O2 generation and callose deposition triggered by HrpNPcc and the disease resistance against bacterial soft rot. Taken together, such results led us to conclude that the assay based on the ETR established in this study can be used as a model for evaluating the effectiveness of plant immunity-intensifying microbes for controlling plant diseases.

Seven bacterial isolates were isolated and identified from green onion and mature bulb (Allium cepa L.) that showing naturally infected soft rot disease. Onion samples used for isolation were collected from different super markets and store houses of Abou-Hamad District, Sharkia Governorate, during 2016/2017 seasons. Seven isolates showed different degree of aggressive pathogenic capability on onion bulbs. Morphological, physiological and biochemical diagnostic properties of the seven bacterial isolates confirmed that one isolate identified as Bacillus polymyxa, three isolates as Pseudomonas cepacia and three isolates as Pectobacterium carotovorum subsp. carotovorum. The seven identified bacterial isolates were compared for their degree of pathogenic capabilities in some different plant hosts. With the exception of chili fruits, the seven bacterial isolates were able to infect fruits, tubers, pods and roots of seventeen host plant species related to seven plant genera. Percentage of rotted onion bulb during storage significantly affected by the packing materials that used in preparing storage package, onion cultivar, maturity of bulb, type of cultivated soil and storage time. Results revealed that good control against onion soft rot could be obtained when mature bulbs of resistant cultivar cultivated in clay soil conducted to good cure program and stored under low temperature and high ventilation conditions.

Phages of the phytopathogenic Pectobacteriaceae species causing black leg and soft rot of potato were investigated. These phages are promising as biocontrol agents to prevent the loss of seed and ware potato tubers. The present work characterizes a new podovirus PP16, infecting a broad range of Pectobacterium carotovorum strains. Based on its genomic composition, phage PP16 was assigned to a separate phylogenetic branch of the genus Phimunavirus, subfamily Autographivirinae. Bacteriophage PP16 efficiently inhibited development of bacterial infection both in vitro and in planta. The field experiment demonstrated a substantial increase of plant germination after the treatment of seed potato with phage PP16.

Plants are exposed to biotic stresses caused by pathogen attack and complex abiotic stresses including heat and drought by dynamic climate changes. To alleviate these stresses, we investigated two bacterial stains, H26-2 and H30-3 in two cultivars ('Ryeokkwang' and 'Buram-3-ho') of Chinese cabbage in plastic pots in a greenhouse. We evaluated effects of bacterial strains on plant growth-promotion and mitigation of heat and drought stresses; the role of exopolysaccharides as one of bacterial determinants on alleviating stresses; biocontrol activity against soft rot caused by Pectobacterium carotovorum subsp. carotovorum PCC21. Strains H26-2 and H30-3 significantly increased fresh weights compared to a MgSO4 solution; reduced leaf wilting and promoted recovery after re-watering under heat and drought stresses. Chinese cabbages treated with H26-2 and H30-3 increased leaf abscisic acid (ABA) content and reduced stomatal opening after stresses treatments, in addition, these strains stably colonized and maintained their populations in rhizosphere during heat and drought stresses. As well as tested bacterial cells, exopolysaccharides (EPS) of H30-3 could be one of bacterial determinants for alleviation of tested stresses in Chinese cabbages, however, the effects were different to cultivars of Chinese cabbages. In addition to bacterial activity to abiotic stresses, H30-3 could suppress incidence (%) of soft rot in 'Buram-3-ho'. The tested strains were identified as Bacillus aryabhattai H26-2 and B. siamensis H30-3 based on 16S rRNA gene sequence analysis. Taken together, H26-2 and H30-3 could be candidates for both plant growth promotion and mitigation of heat and drought stresses in Chinese cabbage.

Solanum tuberosum, commonly known as the potato, is a worldwide food staple. During harvest, storage, and distribution the crop is at risk of mechanical damage. Wounding of the tuber skin can also become a point of entry for bacterial and fungal pathogens, resulting in substantial agricultural losses. Building on the proposal that potato tubers produce metabolites to defend against microbial infection during early stages of wound healing before protective suberized periderm tissues have developed, we assessed extracts of wound tissues from four potato cultivars with differing skin morphologies (Norkotah Russet, Atlantic, Chipeta, and Yukon Gold). These assays were conducted at 0, 1, 2, 3 and 7 days post wounding against the plant pathogen Erwinia carotovora and a non-pathogenic Escherichia coli strain that served as a control. For each of the potato cultivars, only polar wound tissue extracts demonstrated antibacterial activity. The polar extracts from earlier wound-healing time points (days 0, 1 and 2) displayed notably higher antibacterial activity against both strains than the later wound-healing stages (days 3 and 7). These results support a burst of antibacterial activity at early time points. Parallel metabolite profiling of the extracts revealed differences in chemical composition at different wound-healing time points and allowed for identification of potential marker compounds according to healing stage for each of the cultivars. It was possible to monitor the transformations in the metabolite profiles that could account for the phenomenon of temporal resistance by looking at the relative quantities of various metabolite classes as a function of time.

Neobuxbaumia tetetzo (Coulter) Backeberg (tetecho) is a columnar cactus endemic to Mexico. Tetecho plants, flowers, fruits, and seeds play an important role in the semiarid ecosystem, as they serve as a refuge and food for insects, bats, and birds, and are widely used by ethnic groups since pre-Hispanic times. Tetecho is affected by a soft rot that damages the whole plant and causes its fall and disintegration. Eight bacterial colonies of similar morphology were isolated from plants showing soft rot and inoculated in healthy tetecho plants, reproducing typical symptoms of soft rot 9 days after inoculation. Ten representative isolates were selected for phenotypic and genetic identification using 16s rDNA, IGS 16S-23S rDNA, and rpoS genes and for pathogenicity tests on several members of the cactus family and other plants. Based on the results, these bacterial isolates were identified as Pectobacterium carotovorum subsp. brasiliense. Inoculation of this bacteria caused soft rot in different cacti, fruits, leaves, and roots of other plants. This is the first report of the subspecies brasiliense of P. carotovorum causing soft rot and death in cacti in the world and the first report of this subspecies in Mexico.

The pesticides used to tackle potato pathogens, including bacteria, are environmentally damaging, so more sustainable treatments are needed. Because plant defense-related hormones such as methyl jasmonate and salicylic acid and the elicitor chitosan can stimulate plant defense systems, the effect of these compounds was tested by adding them to a watering solution 2 days before inoculating two S. tuberosum cultivars with either Pectobacterium carotovorum strain 5890 or P. atrosepticum strain 889. Growth and the production of several defense phenolic compounds were determined in treated and untreated plants, inoculated or not. P. carotovorum 5890 was more virulent than P. atrosepticum 5889 as reflected by higher levels of phenolic compounds in the plants. The defense-related hormone salicylic acid offered the most protection against the bacteria without interfering with plant growth. Because plants produce and accumulate secondary metabolites for protection against infection, higher production was accompanied by less pathogen damage and higher resistance.

Destructive soft rot Pectobacteriaceae affect a number of vegetable crops and cause high economic loses in the field and storage. The diversity of Pectobacterium and Dickeya causing soft rot of vegetables in Northern Ireland is unknown. This study provides details of Pectobacterium and Dickeya spp. detected in vegetables from several locations in Northern Ireland in the years 2015–2017. Soft rot Pectobacteriaceae were identified based on DNA sequences. Thirty one strains were selected for further phylogenetic analysis based on the recA gene region. Results from the testing of over 3456 potato samples for plant health statutory purposes in years 2005–2017 demonstrated that Dickeya spp. is not the major pathogen causing soft rot or blackleg in Northern Ireland. The most predominant species causing soft rot of vegetables in Northern Ireland were Pectobacterium atrosepticum and Pectobacterium carotovorum subsp. carotovorum. Pectobacterium atrosepticum was also detected on hosts other than potato. Testing of bacteria isolated from carrots led to the detection of P. carotovorum and Dickeya sp. This is the first study to provide knowledge about Pectobacterium and Dickeya spp. diversity causing soft rot of vegetables in Northern Ireland confirmed by real-time PCR and DNA sequences. This is also the first report of the detection of D. aquatica from a source other than water.

Potato (Solanum tuberosum) is the second most important crop after maize in Kenya and plays a major role in national food production and security. Despite its importance, production is constrained by a number of factors, including diseases. Diseases caused by bacteria are a major biotic production constraint. Soft rot and blackleg diseases are considered as important constraints causing considerable losses in many production systems. However, there is scanty information on soft rot and blackleg in potato production systems in Kenya. A limited survey was conducted between September and October 2016 and in December 2016 to January 2017 in four major potato growing regions to determine the identity of pectinolytic bacteria causing blackleg and soft rot disease of potato in Kenya. Tubers and stems with symptoms of blackleg and soft rot disease were collected from 91 randomly selected farms. Identification of the pathogens was done using phenotypic methods which involved culturing on semi-selective medium, biochemical tests, pathogenicity tests and DNA based methods. The results identified occurrence of Pectobacterium carotovorum subsp. carotovorum (6 isolates) in all four regions and Pectobacterium wasabiae (5 isolates) for the first time in Elgeiyo Marakwet. The identity of twelve isolates could not be specified and therefore needs further investigation.

Thionins are a family of antimicrobial peptides. We performed in silico expression analyses of the 44 rice (Oryza sativa) thionins (OsTHIONs). Modulated expression levels of OsTHIONs under different treatments suggest their involvement in many processes, including biotic, abiotic, and nutritional stress responses, and in hormone signaling. OsTHION15 (LOC_Os06g32600) was selected for further characterization based on several in silico analyses. OsTHION15 in O. sativa subsp. indica ‘KDML 105’ was expressed in all of the tissues and organs examined, including germinating seed, leaves, and roots of seedlings and mature plants, and inflorescences. To investigate the antimicrobial activity of OsTHION15, we produced a recombinant peptide in Escherichia coli Rosetta-gami (DE3). The recombinant OsTHION15 exhibited inhibitory activities toward rice-pathogenic bacteria such as Xanthomonas oryzae pv. oryzae and Pectobacterium carotovorum pv. atroseptica, with minimum inhibitory concentrations of 112.6 and 14.1 µg ml−1, respectively. A significant hyphal growth inhibition was also observed toward Fusarium oxysporum f. sp. cubense and Helminthosporium oryzae. In addition, we demonstrated the in planta antibacterial activity of this peptide in Nicotiana benthamiana against X. campestris pv. glycines. These activities suggest the possible application of OsTHION15 in plant disease control.

The causal agent of soft rot disease associated with a cabbage outbreak in Semberija region, Bosnia and Herzegovina, in 2018 was identified and characterized. Symptoms appeared in the form of water-soaked lesions on leaves and specific odour. Disease incidence ranged from 20% to 30%. The causal pathogen was isolated on nutrient agar (NA), King?s B and crystal violet pectate (CVP) media. Eight creamy-white, round and convex bacterial isolates, which produced characteristic pits on CVP medium were taken as representative. They were gram negative, facultative anaerobe, oxidase negative, catalase positive, nonfluorescent on King?s B medium, levan and arginine dehydrolase negative. The isolates were able to cause soft rot on cabbage and potato tuber slices 24 h after inoculation under conditions of high relative humidity. Polymerase chain reaction (PCR) was performed for preliminary identification by using three specific primer sets: F0145/E2477 (specific for Pectobacterium carotovorum subsp. carotovorum), Br1f/L1r (specific for P. carotovorum subsp. brasiliensis) and ECA1f/ECA2r (specific for P. atrosepticum). All isolates produced the band size of 666 bp with F0145/E2477 primer pair, indicating that they belong to the species P. carotovorum subsp. carotovorum. Further genetic characterization was based on sequence analysis of the gapA and mdh housekeeping genes. BLAST analysis confirmed 99.39% (Q. cover 100%, E. value 0.0) and 100% (Q. cover 100%, E. value 0.0) identity of the isolates with P. carotovorum subsp. carotovorum strains deposited in the NCBI database as M34 (KY047594) for gapA and Pcc t0437 (KC337296) for mdh genes, respectively. Phylogenetic analysis showed genetic homogeneity among the cabbage isolates.

The rhizome rot or tip over is a major and emerging disease of banana, causing substantial economic losses. Common cultivars such as Grand Naine, Rasthali and Nendran are highly susceptible to this disease caused by different Pectobacterium species. Understanding the disease etiology and pathogen variability are essential in management programs. Bacterium Pectobacterium carotovorum was isolated from infected rhizomes from 18 locations of Kerala and Tamil Nadu states of India. Pathogenicity of all isolates were confirmed by in vitro inoculation in rhizome bits and in vivo inoculation in rhizomes of three months old plants and pseudostems of two months old tissue cultured plants of cv. Nendran. Isolates were characterized by cultural, morphological, biochemical, physiological and molecular methods. Cultural characterization was carried out on Nutrient agar (NA), Yeast Extract Glucose Calcium Carbonate (YGC), Logan's medium and Nutrient broth. Morphological characterization was carried out by Gram staining, capsule staining and flagellar staining. Biochemical characterization was done through potato and carrot soft rot test, intrinsic antibiotic resistance, growth of bacteria in three and four per cent NaCl and growth of bacteria in CVP medium. Physiological characterization was carried out by growing the bacterium at different temperatures and pH. Based on these results, 18 isolates were allocated to six groups. 16S rDNA regions of representative isolates of each group have been PCR amplified and the 1.5 kb amplicons were sequenced. Homology and phylogeny analyses had shown that all the groups belong to Pectobacterium carotovorum, and two subspecies carotovorum and brasiliense were identified.

In this research, we investigated changes in the concentration of hydrogen peroxide in the potato plants and their cell cultures (Solanum tuberosum L.) of two varieties - Lugovskoy and Lukyanovsky - under the action of the necrotrophic bacterial phytopathogen Pectobacterium carotovorum ssp. сarotovorum (Pcc) and its exometabolites (filtrate devoid of bacterial cells and thermally inactivated bacterial suspension). A biphasic accumulation of hydrogen peroxide is shown to occur in the cell cultures of the potato varieties under investigation infected with Pcc It is established that a thermally inactivated Pcc culture affects both the cell cultures and plant roots of the plants under study by causing a significant change in the generation of hydrogen peroxide in comparison with a filtrate devoid of bacterial cells. When infected with pathogens and their exometabolites, the intensity and dynamics of changes in hydrogen peroxide in the potato plants is significantly higher compared to a suspension cell culture. The intensity and dynamics of changes in the generation of hydrogen peroxide indicate the development of a systemic induced resistance in the studied potato varieties to Pcc bacteria and their exometabolites.

A novel antimicrobial formulation based on carboxymethylcellulose (CMC) spray-coated Cu2+ intercalated montmorillonite (MMT) nanocomposite material was prepared and its morphology, internal structure, and bonding interactions were studied. Meanwhile, the antibacterial efficacy and release behavior of Cu2+ was also determined. PXRD patterns indicated the intercalation of Cu2+, while FTIR spectra and TGA traces confirmed the association of Cu−MMT with CMC. SEM study revealed the improvement of nanocomposites by CMC, without disturbing the clay structure. TEM and EDAX studies indicated the distribution of Cu (copper) throughout the composite. In vitro antibacterial assays performed with Erwinia carotovora revealed effective bacterial growth suppression, indicating the potential of this material in controlling soft rot of potatoes (Solanum tuberosum), also observed was a connection between growth inhibition and concentration of CMC spray coats indicating a positive relationship between Cu2+ release and concentration of the CMC coatings. The activity pattern of the nanocomposite displayed a significant degree of sustained-release behavior.

A novel antimicrobial formulation based on carboxymethylcellulose (CMC) spray-coated Cu2+ intercalated montmorillonite (MMT) nanocomposite material was prepared and its morphology, internal structure, and bonding interactions were studied. Meanwhile, the antibacterial efficacy and release behavior of Cu2+ was also determined. PXRD patterns indicated the intercalation of Cu2+, while FTIR spectra and TGA traces confirmed the association of Cu−MMT with CMC. SEM study revealed the improvement of nanocomposites by CMC, without disturbing the clay structure. TEM and EDAX studies indicated the distribution of Cu (copper) throughout the composite. In vitro antibacterial assays performed with Erwinia carotovora revealed effective bacterial growth suppression, indicating the potential of this material in controlling soft rot of potatoes (Solanum tuberosum); also observed was a connection between growth inhibition and concentration of CMC spray coats indicating a positive relationship between Cu2+ release and concentration of the CMC coatings. The activity pattern of the nanocomposite displayed a significant degree of sustained-release behavior.

Background Several chemical bactericides were applied for controlling soft rot bacteria, Pectobacterium carotovorum subsp. carotovorum, which causes the destructive soft rot disease to many economically important vegetables, but because of their toxic hazards on human and environment became limit. The biocontrol was applied to control many plant pathogens. Therefore, this work is aimed to study the antagonistic activity of bacterial agents, i.e. Bacillus subtilis, Bacillus pumilus, Bacillus megaterium and Pseudomonas fluorescens, and fugal agents, i.e. Trichoderma harzianum, Trichoderma viride and Trichoderma virens, to control bacterial soft rot disease under in vitro and in vivo tests. Results The tested treatments could protect the potato tubers against the development of soft rot. T. viride and T. virens were highly effective in reducing soft rot symptoms on inoculated potato tuber slices, when applied at the same time or 2 h before pathogen inoculation, while B. megaterium and T. harzianum were highly effective when applied at the same time or 2 h after pathogen inoculation. In whole potato tubers technique, B.pumilus highly protected the stored potato tuber under artificially infection conditions, than P. fluorescens, T. harzianum, B. subtilis, T. viride, T. virens and B. megaterium, respectively. Conclusion Application of fungal agents or specify the bacterial species can play an important role in controlling bacterial soft rot disease in vegetables and increase the stored periods of potato tubers under storage conditions without any toxic effects.

Prickly pear Opuntia ficus-indica (L.) Mill.,1768) is a succulent plant belonging to the Cactaceae family, native to Central America but now diffused both in the the Mediterranean area (mainly Sicily, Calabria, Puglia, Sardinia and Malta) and in the temperate areas of America, Africa, Asia and Oceania. The oil obtained from its seeds, rich in polyunsatured fatty acids, has also known antimicrobial and antioxidant properties. Herein we evaluated not only the capacity of this oil to inhibit the formation of biofilm by different pathogens but also to block the metabolic changes taking place in the microbial cells included in the biofilm. The oil was capable to inhibit at 38.75% the biofilm of Escherichia coli just at a concentration of 1 microliter/ml, and, when tested against Pseudomonas aeruginosa, the inhibition reached the 74%. The oil was also effective against Pseudomonas aeruginosa (71.84% of inhibition) and the phytopathogen Pectobacterium carotovorum (63.06%). The metabolic activity of the microbial cells present within the biofilm was also strongly inhibited and, when the oil was tested against P. carotovorum, microbial cell metabolism was completely inhibited. The action of the prickly pear seeds oil was effective also in blocking at 64.97 % the metabolism of Listeria monocytogenes cells, which therefore had conversely demonstrated to be more resistant compared to the other bacteria (31% of biofilm inhibition). Data from the present study indicates a wide field of application of this oil, with interesting potentialities for food and health purposes.

Strains of genus Pectobacterium are major cause of soft rot diseases in fruits and vegetables worldwide. Traditional control methods have not been very successful in combating the pathogenesis. As a result there has been an emerging need for developing an alternative ecofriendly and economical strategy. The pathogenesis of Pectobacterium sp. is mediated by quorum sensing (QS) and approaches based on inhibition of QS system to shut down the virulence genes without affecting growth of the pathogen may serve the purpose. Bacillus sp. OA10 associated with purple sponge Haliclona sp. was found to possess extracellular quorum quenching activity. The OA10 extract inhibited QS dependent virulence of Pectobacterium carotovorum subsp. carotovorum BR1 (PccBR1) at low concentrations (0.2 mg) as evident from 77.56 ± 6.17% reduction in potato maceration with complete inhibition by 0.8 mg. Inhibition of plant cell wall degrading enzymes (PCWDE) and carbapenem production by PccBR1 in presence of OA10 extract indicated disruption of the two QS pathways ExpI/ExpR and CarI/CarR in PccBR1. Bacillus sp. OA10 was not found to degrade acyl homoserine lactone (AHL), instead exhibited QSI activity by probably inhibiting AHL synthesis in PccBR1. Absence of enzymatic principle in quorum sensing inhibitor (QSI) is beneficial as enzymes may get inhibited by various factors during their application. OA10 extract did not affect growth of PccBR1, thereby reducing the chance of developing resistance against the QSI. Thus, Bacillus sp. OA10 can prove to be a good prospective candidate for QSI based novel biocontrol formulations.

Managed aquifer recharge (MAR) can provide irrigation water and overcome water scarcity in agriculture. Removal of potentially present plant pathogens during MAR is essential to prevent crop diseases. We studied the die-off of three plant pathogenic bacteria in water microcosms with natural or filtered tile drainage water (TDW) at 10 and 25°C and with natural anoxic aquifer water (AW) at 10°C from a MAR site. These bacteria were: Ralstonia solanacearum (bacterial wilt), and the soft rot Pectobacteriaceae (SRP) Dickeya solani and Pectobacterium carotovorum sp. carotovorum (soft rot, blackleg). They are present in surface waters and cause destructive crop diseases worldwide which have been linked to contaminated irrigation water. Nevertheless, little is known about the survival of the SRP in aqueous environments and no study has investigated the persistence of R. solanacearum under natural anoxic conditions. We found that all bacteria were undetectable in 0.1 mL samples within 19 days under oxic conditions in natural TDW at 10°C, using viable cell counting, corresponding to 3-log10 reduction by die-off. The SRP were no longer detected within 6 days at 25°C, whereas R. solanacearum was detectable for 25 days. Whereas in anoxic natural aquifer water at 10°C, the bacterial concentrations declined slower and the detection limit was reached within 56 days. Finally, we modelled the inactivation curves with a modified Weibull model that can simulate different curve shapes such as shoulder phenomena in the beginning and long tails reflecting persistent bacterial populations. The non-linear model was shown to be a reliable tool to predict the die-off of the analysed plant pathogenic bacteria, suggesting its further application to other pathogenic microorganisms in the context of microbial risk assessment.

Some molecular aspects of Solanum tuberosum immune response to the pectobacterial infection were studied.

Bacterial metal reducers were isolated from water samples collected from harsh condition locations in Egypt. Four selected isolates were identified as Enterococcus thailandicus, Pseudomonas putida, Marinobacter hydrocarbonoclasticus, and P. geniculata for Copper (Cu), Iron (Fe), Cobalt (Co) and Zinc (Zn) Nanoparticles (NPs) production sequentially. Nitrate reductase enzyme was assayed for bacterial isolates which demonstrated that P. putida, and M. hydrocarbonoclasticus have the maximum enzyme production. The produced NPs were characterized by using XRD, TEM, UV–VIS spectroscopy. Magnetic properties for all selected metals NPs were measured using Vibrating Sample Magnetometer (VSM) and demonstrated that FeNPs recorded the highest magnetization value. The antibacterial activity of selected metals NPs was tested against some phytopathogenic bacteria causing the following diseases: soft rot (Pectobacterium carotovorum, Enterobacter cloacae), blackleg (Pectobacterium atrosepticum and Dickeya solani), brown rot (Ralstonia solanacearum), fire blight (Erwinia amylovora) and crown gall (Agrobacterium tumefaciens). All metals NPs showed an antagonistic effect against the tested isolates, particularly, FeNPs showed the highest antibacterial activity followed by CuNPs, and ZnNPs. Due to the small size, high reactivity, and large surface area of biologically synthesized NPs, they are used as a good disinfector, and can be considered as a new and alternative approach to traditional disease management methods.