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Bacterial soft rot is a destructive disease that restricts the development of the konjac (Amorphophallus konjac K. Koch ex N.E.Br) industry. The objective of this study was to investigate how soft rot disease affects bacterial communities associated with the roots of konjac plants growing under a pure Robinia pseudoacacia plantation. Three sampling sites affected by different degrees of soft rot damage were selected based on the disease incidence [0%, non-diseased (ND); 4.2%, moderately diseased (MD); and 18.6%, highly diseased (HD)]. The variation in soil and root bacterial diversity and community composition among the sampling sites was determined by Illumina HiSeq sequencing of the V3–V4 hypervariable regions of the bacterial 16S rRNA gene. The results showed that the contents of soil organic matter and available nutrients (N, P, and K) increased with increasing damage degree, whereas higher damage degree resulted in lower soil pH and enzymatic activity (sucrase, urease, catalase, and polyphenol oxidase). The composition of root-associated bacterial communities differed among the three sampling sites. Proteobacteria was the most dominant bacterial phylum in all soil and root samples. Pseudomonas, Bacillus, Rhizobium, and Streptomyces were the most abundant in all samples from the ND sites, whereas Pectobacterium carotovorum and Serratia were predominant in the samples from the MD and HD sites. The abundance and alpha diversity of root-associated bacteria were significantly higher (p < 0.05) in the ND sites than in the diseased sites. The results suggested pronounced differences in the abundance, alpha diversity, and community composition of bacteria associated with the roots of konjac plants affected by different degrees of soft rot damage. Such differences in bacterial community structure were related to dynamic changes in soil variables, especially soil available potassium content, sucrase activity, and urease activity. Analysis of the dominant root-associated bacterial taxa offers an approach to predict the damage degree due to soft rot in konjac and provides evidence for the prevention of this soil-borne disease via microecological regulation.

The current investigation was planned to apply some biotic and abiotic treatments singlely and/or combined to control bacterial soft rot diseases of lettuce under field conditions in Qaha region, Qalyubia Governorate, Egypt. The application of resistance inducers (jasmonic acid and salicylic acid), antibiotics (norfloxacin and tetracycline) and bio-agents (isolates of B. subtilis and Ps. fluorescens) significantly reduced the disease severity as a single treatment compared to the control treatment. Obtained results indicated that resistance inducers appeared to be most effective against bacterial soft rot disease of lettuce compared with other treatments, while antibiotics were less effective at controlling the disease. However, the interaction between bio-agents as soil drench treatment, antibiotics, or resistance inducers as foliar treatment significantly reduced the severity of lettuce bacterial soft rot disease compared with the control treatment. Furthermore, the interaction between disease severity was more reducted with interaction treatments between Ps. fluorescens isolate rather than interact with treatments between B. subtilis isolate and other treatments. However, the interaction between the isolate of Ps. fluorescens as bio-agent treatment or norfloxacin as antibiotic or salicylic acid as a plant resistance inducer, were the most effective methods to control the disease compared with other treatments. Meanwhile, the interaction between resistance inducers and antibiotics as foliar treatments were significantly reduced from the severity of lettuce bacterial soft rot disease compared with the control treatment. Disease severity was more reduced with the application of interaction between norfloxacin and resistance inducers than the interaction between tetracycline and resistance inducers. Meanwhile, the severity of the disease decreased more with the application of interaction between salicylic acid and antibiotics than the interaction between jasmonic acid and antibiotics. Generally, all combination treatments were more efficient than single treatments alone to significantly manage the spread and the infection of the disease compared to the untreated control.

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.

Background Pectobacterium carotovorum subsp. brasiliense is a broad host range bacterial pathogen, which causes blackleg of potatoes and bacterial soft rot of vegetables worldwide. Production of plant cell wall degrading enzymes is usually critical for Pectobacterium infection. However, other virulence factors and the mechanisms of genetic adaptation still need to be studied in detail. Results In this study, the complete genome of P. carotovorum subsp. brasiliense strain SX309 isolated from cucumber was compared with eight other pathogenic bacteria belonging to the Pectobacterium genus, which were isolated from various host plants. Genome comparison revealed that most virulence genes are highly conserved in the Pectobacterium strains, especially for the key virulence determinants involved in the biosynthesis of extracellular enzymes and others including the type II and III secretion systems, quorum sensing system, flagellar and chemotactic genes. Nevertheless, some variable regions of the T6SS and the CRISP-Cas immune system are unique for P. carotovorum subsp. brasiliense. Conclusions The extensive comparative genomics analysis revealed highly conserved virulence genes in the Pectobacterium strains. However, several variable regions of type VI secretion system and two subtype Cas mechanism-Cas immune systems possibly contribute to the process of Pectobacterium infection and adaptive immunity. Electronic supplementary material The online version of this article (10.1186/s12864-019-5831-x) contains supplementary material, which is available to authorized users.

Bacterial soft rot is a devastating disease in potato. However, it is difficult to evaluate disease resistance because there are a number of ways the bacterium can infect tubers, including through lenticels, in bruised tissue, and through wounds. Thus, various screening methods have been developed to evaluate resistance in potato tubers. The methods published to date are limited in their ability to measure symptoms quickly and accurately in a large number of samples. Therefore, we developed a new high throughput phenotyping method to evaluate soft rot disease symptoms the assistance of image analysis software. This method has proven to be very efficient in evaluating disease symptoms.

Bacterial soft rot caused by Dickeya zeae MS1 (Erwinia chrysanthemi) is one of the most devastating banana diseases worldwide. However, knowledge of the development and ecological interactions of D. zeae MS1 biofilm is limited. Here, we visualized the development and architecture of D. zeae MS1 biofilm using confocal laser scanning microscopy, and we evaluated the ability of D. zeae MS1 to form biofilms under different environmental conditions (carbon sources, temperatures, pH levels and mineral elements) using a microtiter plate assay. We found that the development of D. zeae MS1 biofilm could be categorized into four phases and that mature biofilm consisted of a highly organized architecture of both bacterial cells and a self-produced matrix of extracellular polysaccharides. Furthermore, sucrose was the most suitable carbon source for supporting the growth of biofilm cells and that 32 °C and pH 7.0 were the most favorable of the temperatures and pH levels examined. Meanwhile, the addition of Ca2+, Fe2+, K+ and Na+ enhanced the formation of biofilm in minimal medium cultures, whereas 2.5 mM Cu2+ and Mn2+ was inhibitory. A better understanding of biofilm formation under different environmental parameters will improve our knowledge of the growth kinetics of D. zeae MS1 biofilm.

Bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum is a devastating plant disease in calla lily (Zantedeschia spp.). Considering the economic value of calla lily in the cut flower industry, effective means for controlling this disease are urgently needed. A screening of 12 isolates yielded strain BS as the best antagonist against P. carotovorum. The isolate with excellent antibacterial activity was identified as belonging to Myxococcus sp. Further research indicated that predator-prey interactions involving extracellular vesicles are involved in the antibacterial behavior, and that efficient predation followed by fruiting body formation was responsible for the adaption and colonization ability of BS in soil. Pot experiments showed that strain BS significantly decreased the incidence of soft rot of calla lily to 19.8% from 75.0%, and the disease index was lowered to 6.3% from 62.5%. When the strain BS was applied to the soil, the pre-treated calla lily plants displayed significantly higher levels of growth and greater number of progeny tubers than untreated controls. Due to its multiple beneficial traits, strain BS has the potential to be developed into a plant growth promoting and biocontrol agent for integrated disease and health management strategies.

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.

Background Soft rot disease caused by Pectobacterium carotovorum was observed in various crops which lead to yield shortages and economic losses. Main body Therefore, both in vitro and in vivo experiments, aim to assess the effect of nanoparticles and biological treatments to control soft rot disease in sugar beet plant. The treatments comprised three silver nanoparticles (Ag NPs) concentrations (50, 75, and 100 ppm), three Spirulina platensis extract concentrations (50, 75, and 100%), and Bacillus subtilis (1 × 109 CFU ml) 100%. Under in vitro condation, results of the antibacterial activity showed that the zones of inhibition recorded 4.33 cm for 100 ppm Ag NPs, 0.43 cm for 100% algal extract, and 0.2 cm for bacterial treatments. Also, disease incidence % of bacterial soft rot was significantly decreased in all treatments in pot and field experiments. For resistant enzymes activity, B. subtilis 100% showed the most effect (84 mg min−1), followed by S. platensis extract 75%, (57 mg min−1), and Ag NPs 75 ppm (44 mg min−1), for poly phenol oxidase (PPO) at 81 days after sowing (DAS), but at 102 DAS revealed opposite results. On the contrary, peroxidase (PO) at 81 DAS showed different effects where treatment with S. platensis extract 100% increased it significantly (0.546 mg min−1) compared to control (0.535 mg min−1). The same trend was observed at 102 DAS. These results were reflected on sugar quality where Ag NPs 100 ppm treatment recorded the highest significant value (20.5%) followed by S. platensis 75% (19 %); however, the differences among them were not statistically significant. Conclusion This study indicated that the potential benefits of using silver nanoparticles and two biological treatments to control soft rot disease in sugar beet (Beta vulgaris L).

Soft rot disease caused by Pectobacterium spp. is responsible for severe agricultural losses in potato, vegetables, and ornamentals. The genus Zantedeschia includes two botanical groups of tuberous ornamental flowers that are highly susceptible to the disease. Previous studies revealed that Z. aethiopica, a member of the section Zantedeschia, is significantly more resistant to Pectobacterium spp. than members of the same genus that belong to the section Aestivae. During early infection, we found different patterns of bacterial colonization on leaves of hosts belonging to the different sections. Similar patterns of bacterial colonization were observed on polydimethylsiloxane (PDMS) artificial inert replicas of leaf surfaces. The replicas confirmed the physical effect of leaf texture, in addition to a biochemical plant–bacterium interaction. The differential patterns may be associated with the greater roughness of the abaxial leaf surfaces of Aestivae group that have evolutionarily adapted to mountainous environments, as compared to Zantedeschia group species that have adapted to warm, marshy environments. Transverse leaf sections also revealed compact aerenchyma and reduced the total volume of leaf tissue air spaces in Aestivae members. Finally, an analysis of defense marker genes revealed differential expression patterns in response to infection, with significantly higher levels of lipoxygenase 2 (lox2) and phenylalanine ammonia lyase (pal) observed in the more resistant Z. aethiopica, suggesting greater activation of induced systemic resistance (ISR) mechanisms in this group. The use of Zantedeschia as a model plant sheds light on how natural ecological adaptations may underlay resistance to bacterial soft rot in cultivated agricultural environments.

Bacterial soft rot diseases devastate a wide range of crops, vegetables and ornamental plants worldwide. Amongst the most damaging agents of these diseases are members of the Pectobacterium and Dickeya genera belonging to the family Pectobacteriaceae in the order Enterobacterales. As an introduction to the topics of this book, this chapter presents a brief overview on taxonomy history, presence in multiple environments, disease characteristics, population dynamics, management and economic impact of these bacteria.

Background: Bacterial soft rot caused by members of the soft rot Pectobacteriaceae afflicts plant production of both vegetable and ornamental crops. Recent outbreaks highlight Dickeya sp. in the etiology of this disease in potatoes. Since there is a lack of control strategies for these diseases, alternative approaches have been suggested, including the use of biological control mediated by bacteriophages (phages). However, phages infecting many of these members are still undiscovered or poorly described. Materials and Methods: Two phages targeting Dickeya dadantii subsp. dadantii (NCPPB 4097) were isolated from household organic waste and purified. They were then further characterized using whole-genome sequencing and comparative genomics, transmission electron microscopy, latent period and burst size. Results: Dickeya phage Sucellus displayed Siphovirus morphology and had a genome of 39,826 bp with very limited similarity to any previously described phages. Dickeya phage Amaethon had a Podovirus morphology with a genome comprising 41,436 bp and limited similarity to phages in the Kafuna genus. The phages exhibited burst sizes of app. 94 and 240 virions per cell with latent periods of 91 and 86 minutes for Sucellus and Amaethon, respectively. While both phages had similar adsorption efficiencies and latent periods, the rise periods for the two phages diverged markedly, highlighting an odd growth pattern. Conclusions: Together, the two phages isolated here expand the known diversity of phages infecting the important plant pathogen D. dadantii. As they both share limited similarity to previously described groups of phages, they likely constitute novel genera within their respective groups.

Bacterial soft rot is a destructive disease affecting calla lily production, and it is mainly caused by Pectobacterium carotovorum (Pc). In 2019, this destructive disease was observed in the Shandong and Jiangsu Provinces of China and resulted in serious economic losses for commercial greenhouse producers of ornamental plants. The disease symptoms on leaves and stems were yellow and dark brown patches, and then water-soaked lesions that turned to wet rot occurred on the stems. In total, we obtained twenty-eight calla lily soft rot samples collected from Shandong and Jiangsu. Fifteen colonies on LB medium were milky white, nearly round, with a smooth surface and neat edges. The soft rot symptoms in calla lily caused by artificial inoculation were the same as the natural symptoms in the field. Based on the phenotypic properties determined by morphological, biochemical and physiological analyses, 16S ribosomal DNA gene sequence analysis, and multilocus sequence analysis, the pathogen was identified as P. aroidearum. In addition, all P. aroidearum strains exhibited high virulence and a wide host range on monocotyledonous and dicotyledonous plants. This study is the first official report of P. aroidearum causing calla lily soft rot in China, and the results contribute to a better understanding of the disease.

The over and repeated use of chemical bactericides to control plant bacterial diseases has resulted in unwanted effects, such as environmental pollution, residual toxicity, and resistance buildup in bacterial pathogens. Many previous studies have aimed to develop biological control agents to replace chemical bactericides. In this study, the antibacterial efficacy of the fermentation broth of Paenibacillus elgii JCK-5075 and its antibacterial compounds were evaluated against plant pathogenic bacteria, using both in vitro and in vivo bioassays. Pelgipeptins (PGPs) A, B, C, and D that were isolated from P. elgii JCK-5075 displayed broad-spectrum antibacterial activity against various plant pathogenic bacteria. The fermentation broth of P. elgii JCK-5075, at 5-fold dilution, effectively suppressed the development of tomato bacterial wilt, Kimchi cabbage soft rot, and red pepper bacterial leaf spot in pot experiments with control values of 81, 84, and 67%, respectively. PGP-A and C, at 200 μg/ml, were also found to markedly reduce the development of Kimchi cabbage bacterial soft rot by 75% and tomato bacterial wilt by 83%, respectively, and their disease control efficacy was comparable to that of oxolinic acid with control values of 81 and 85%, respectively. Additionally, the antibacterial activity of PGP-C was found to be directly correlated with membrane damage mechanisms. These results indicates that P. elgii JCK-5075 producing PGPs could be used as a biocontrol agent for the control of plant bacterial diseases. This is the first report on the in vitro and in vivo antibacterial activity of PGPs against bacterial plant pathogens.

Dickeya zeae is the causal agent of bacterial soft rot disease, with a wide range of hosts all over the world. At present, chemical agents, especially agricultural antibiotics, are commonly used in the prevention and control of bacterial soft rot, causing the emergence of resistant pathogens and therefore increasing the difficulty of disease prevention and control. This study aims to provide a safer and more effective biocontrol method for soft rot disease caused by D. zeae. The spot-on-lawn assay was used to screen antagonistic bacteria, and three strains including SC3, SC11 and 3-10 revealed strong antagonistic effects and were identified as Pseudomonas fluorescens, P. parafulva and Bacillus velezensis, respectively, using multi-locus sequence analysis (MLSA) based on the sequences of 16S rRNA and other housekeeping genes. In vitro antimicrobial activity showed that two Pseudomonas strains SC3 and SC11 were only antagonistic to some pathogenic bacteria, while strain 3-10 had broad-spectrum antimicrobial activity on both pathogenic bacteria and fungi. Evaluation of control efficacy in greenhouse trials showed that they all restrained the occurrence and development of soft rot disease caused by D. zeae MS2 or EC1. Among them, strain SC3 had the most impressive biocontrol efficacy on alleviating the soft rot symptoms on both monocotyledonous and dicotyledonous hosts, and strain 3-10 additionally reduced the occurrence of banana wilt disease caused by Fusarium oxysporum f. sp. cubensis. This is the first report of P. fluorescens, P. parafulva and B. velezensis as potential bio-reagents on controlling soft rot disease caused by D. zeae.

Soft rot bacteria of the Pectobacterium and Dickeya genera are Gram-negative phytopathogens that produce and secrete plant cell wall-degrading enzymes (PCWDE), the actions of which lead to rotting and decay of their hosts in the field and in storage. Host chemical signals are among the factors that induce the bacteria into extracellular enzyme production and virulence. A class of compounds (Class I) made up of intermediate products of cell wall (pectin) degradation induce exoenzyme synthesis through KdgR, a global negative regulator of exoenzyme production. While the KdgR&minus, mutant of P. carotovorum is no longer inducible by Class I inducers, we demonstrated that exoenzyme production is induced in this strain in the presence of extracts from hosts including celery, potato, carrot, and tomato, suggesting that host plants contain another class of compounds (Class II inducers) different from the plant cell wall-degradative products that work through KdgR. The Class II inducers are thermostable, water-soluble, diffusible, and dialysable through 1 kDa molecular weight cut off pore size membranes, and could be a target for soft rot disease management strategies.

Pectobacterium carotovorum subsp. carotovorum (Pcc) causes bacterial soft rot on a wide range of crops worldwide, especially in countries with warm and humid climates. This study was conducted to establish an efficient screening method for resistant cultivars of radish (Raphanus sativus) to bacterial soft rot. Resistance degrees of 60 commercial radish cultivars to the Pcc KACC 10421 isolate were investigated. For further study, six radish cultivars (Awooriwoldong, YR Championyeolmu, Jeonmuhumu, Bitgoeunyeolmu, Sunbongaltari, Housecheongok) showing different level of resistance to the bacterium were selected. The development of bacterial soft rot on the cultivars was tested according to several conditions such as incubation temperature, seedling stage of radish, inoculum concentration to develop the disease. On the basis of the results, we suggest that an efficient screening method for resistant radish to Pcc is to inoculate twenty-day-old seedlings with a bacterial suspension of Pcc at a concentration of 8×10⁵ cfu/ml and then to cultivate the plants in a growth room at 25°C and 80% RH with 12-hour light per day.

Predictions of distributions of resistance phenotypes have been attempted for major diseases in wild potato germplasm. Interestingly, no consistent taxonomic or biogeographic predictors have been identified. However, an important lesson learned was that there are interactions among host plants, environmental factors, and characters of the pathogens. A logical extension of the predictivity project is to examine the dynamics of resistances when multiple biotic stresses are involved. In this study, we found that populations susceptible to a foliar feeding pest [Colorado potato beetle, Leptinotarsa decemlineata (Say)] are resistant to a bacterial pathogen [Pectobacterium carotovorum subsp. carotovorum (Jones, 1901; Hauben et al. 1999)]. We propose that wounds caused by the insect pest allow the bacterial pathogen to gain entry and cause disease. This would lead to strong selection pressure for resistance to the bacterial pathogen. Consequently, when searching for traits of interest in germplasm collections, it is important to consider the complex biotic and abiotic environments in which the source populations evolved.

In the last decade, diseases of bacterial origin in onions have increased and this has led to significant losses in production. These diseases are currently observed in both the Old and New Worlds. The present study aimed to evaluate whether the irrigation method influences the incidence of diseases of bacterial origin.; Results: In cases where the inoculum was natural, the initial incidence of soft bacterial rot did not manifest in any treatment in the first year, whereas, at the end of the conservation period, all treatments had increased incidences of infection. Sprinkler irrigation (8%) was statistically differentiated from the other treatments, for which the final incidence was similar (4.5%). For all irrigation treatments, the final incidence of bacterial soft rot decreased or remained stable towards the end of the cycle, with the exception of sprinkler irrigation in 2015, which increased.; Conclusion: From the results of the present study, it can be inferred that the irrigation method does have an influence on the incidence of diseases of bacterial origin in the post-harvest stage for onions. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

Bacterial soft rot disease is one of the most important factors affecting potato production in Jordan. Based on biochemical and physiological analyses, Jordanian isolates of soft rot from potato were identified as Pectobacterium carotovorum subspecies carotovorum (DYE 1969). Phylogenetic analysis using pmrA gene sequence data showed that isolates from different regions were closely related to each other, whereas little genetic diversity was observed between these isolates. A DNA marker was developed from nucleotide sequences of the pmrA gene and a 318 bp fragment was polymerase chain reaction (PCR) amplified specifically from P. carotovorum subspecies carotovorum isolates, which could be used for detection of the disease in potato tubers. Key words: Potato soft rot, Solanum tuberosum, genetic diversity, pmrA gene, Pectobacterium carotovorum subspecies carotovorum, Jordan.

Pectobacterium sp. causes the bacterial soft rot diseases in a wide range of plant species. In this study, random gene-knockout with transposon was conducted to explore genes involved in pathogenicity. As a result, I found 38 mutant strains of which pathogenicity was decreased. The determination of mutated genes revealed that 10 genes such as glycosyltransferase, RNA-binding protein hfq and Tol-Pal system are necessary for complete virulence.

A strong oxidizing compound, peroxyacetic acid (PAA) which formed by mixing hydrogen peroxide (H2O2) with acetic acid, gave a promising control approach against soft rot bacteria. Since, wetting fleshy plant organs by PAA significantly reduced soft rot severity as compared to check organs (untreated organs). All tested vegetable fruits, i.e. eggplant, pepper, tomato, cucumber, squash and okra plus potato tubers were responded to PAA treatment. However, pepper fruits showed the highest protection followed by eggplant, squash, cucumber and okra, while tomato fruits showed the least protection value. Potato tubers gave 50% protection. Storage temperature is important, since at 35oC decay was developed at short period while at 5oC was delayed. Efficacy of peroxyacetic acid to reduce bacterial soft rot was differed significantly with both storage temperatures and the tested vegetable fruits or tubers. Either wounded or sound treated vegetable fruits or tubers responded to PAA treatment that showed significant reduction in soft rot severity by 41.1-72.2% in case of unwounded treated vegetable fruits or tubers by about 20–66% in case of wounded treated vegetable fruits or tubers. PAA was more effective to reduce bacterial soft rot severity when unwounded fruits or tubers were pre-inoculation treated.

Our purpose was to evaluate chemotactic response of Ginseng bacterial soft-rot to ginseng root exudates. The exudates of plant roots has a significant influence on the population changes of rhizosphere microorganisms and chemotaxis is an important way in which many pathogens sense the signals of host plants and invade the host plants. In this study, with the capillary method, we tested the chemotactic responses of Ginseng bacterial soft-rot for three ginseng roots exudates under four chemotactic parameters (concentration, temperature, pH and time). The results showed that the chemotatic response of the Ginseng bacterial soft-rot for the ginseng roots exudates at the water layer where pH = 7 and the concentration was 0.0125 mg/L reached its peak value under the circumstance that the exudates was cultivated for 60 min at 25 °C. The chemotatic ratios were respectively 124.89% and 89.44%. For the butanol extract layer and the petroleum ether faction at the concentration of 0.125 mg/L and the pH value at 7, the ginseng roots exudatess reached peak values at 25 °C and 30 °C and 60 min and 75 min respectively, and the chemotatic ratios were respectively 139.64% and101.87%, and 115.29% and 81.36%. The three ginseng roots exudates had positive effects for the chemotaxis of the Ginseng soft-rot bacteria, but the effect declined as the concentration increased.

Bacterial soft rot caused by Pectobacterium carotovorum has brought huge economic losses to post-harvest vegetables. In this study, vegetables were used as raw materials to produce food-grade antibacterial products, fermented by lactic acid bacteria, to control P. carotovorum. A total of 32 kinds of vegetables were fermented by Lactobacillus paracasei WX322, results showed that 31 vegetable fermentation products had antibacterial activities at different levels. The green pepper fermentation antibacterial product (GPFA) had the highest activity and was selected for further analysis. On the 7th day of fermentation, the antibacterial activity of GPFA reached the maximum, with 640 AU/mL. Two bacteriocins, GP-19 and EP-20, were identified by LC-MS/MS. Growth curve and time-kill curve showed that the GPFA could effectively inhibit and kill P. carotovorum at a dose-dependent manner. SYTO9TM/PI staining observation further confirmed its bactericidal ability. Meanwhile, GPFA treatment led to irregular deformation of cells with rough surface observed using scanning electron microscopy (SEM). Moreover, in vivo assay showed that GPFA treatment significantly reduced the disease incidence and decay degree of pepper soft rot. In addition, GPFA treatment could prolong the shelf life of fresh-cut bell pepper. This study indicates that antibacterial products based on vegetable fermentation can provide a new method for the control of vegetable soft rot.

Pak choi (Brassica rapa subsp. chinensis) is an important vegetable crop native to China, known for high water content and low caloric value, containing high quality of protein, carbohydrates, fiber, vitamins, minerals, and secondary plant metabolites (Acikgoz, 2016). A pak choi field (8,000 sq. ft.) on Oahu, Hawaii, was visited in May 2020. About 10% plants were infected and showed characteristic symptoms of soft rot, wet lesions, macerated infected stem and necrotic leaves (Figure1A-D); leading to the suspect of one of the most devastating bacterial pathogens within genus Pectobacterium (Boluk et al. 2020; Li et al. 2019; Arizala et al. 2020; Arizala and Arif, 2019). Four infected plants were collected from the field, and stems were surface sterilized with 0.6% sodium hypochlorite solution for 30 sec, followed by three consecutive rinses in distilled water. The stems were aseptically macerated, streaked on Crystal violet pectate medium (CVP) (Hélias et al. 2011), and incubated for 48 h at 26 ± 2°C. The peculiar morphological characteristic of pectolytic bacterial pathogen, forming pits on CVP, were observed (Meng et al. 2016) (Figure 1E). Purification of bacterial colonies were done by re-streaking of a single colony on dextrose peptone agar (DPA-without tetrazolium chloride; Norman and Alvarez 1989). DNA was isolated from bacterial cultures using the DNeasy Blood and Tissue Kit (Qiagen, Germantown, MA), respectively. Molecular identification of four strains (PL243-246) were performed by the sequencing region of the housekeeping gene dnaA (chromosomal replication initiation protein) using Pec. dnaA-F1/R1 primer set (Dobhal et al. 2020). The amplified PCR product was enzymatically cleaned using ExoSAP-ITTM (Affymetrix Inc, Santa Clara, CA), and sent for sequencing at the GENEWIZ facility (Genewiz, La Jolla, CA) using both forward and reverse primers. The dnaA gene sequences were aligned using Geneious, and manually edited to remove the errors. The consensus sequences were analyzed with the NCBI BLASTn tool and were deposited in the NCBI GenBank under the accession numbers MT899920-MT899923. The NCBI BLASTn report indicated that all the sequences shared 99-100% identity and query cover with Pectobacterium brasiliense accession numbers MN544627-29. A phylogenetic analysis, using Geneious, was performed with the dnaA sequences representing different Pectobacterium spp., all strains grouped within the clade of P. brasiliense (Figure 2; Arizala et al, 2020). A pathogenicity assay was carried out in three replications on pak choi grown in pots containing commercial pot mixture, and maintained in the controlled-greenhouse (temperature 26-30°C; relative humidity 50-58%). Three-weeks old plant stems were artificially inoculated with 100 µl bacterial suspensions of PL243 (1.3x 10⁸ CFU/ml), PL244 (1.2x 10⁸ CFU/ml), PL 245 (1.2x 10⁸ CFU/ml) and PL246 (1.1x 10⁸CFU/ml); control plants were inoculated with 100 µl of distilled water (Figure 1F). Two days after inoculation, the soft rot and wilting symptoms (Figure 1G-H), similar to the ones observed on the field, were developed for all four strains tested. Bacteria was successfully re-isolated from the inoculated plants; DNA was isolated, amplified, sequenced for dnaA region and analyzed for 100% homology with original strains, to fulfill Koch's postulates. Based on the molecular characteristics re-isolates were identical to the original strains. To the best of our knowledge, this is the first report of P. brasiliense on pak choi in the USA. Recent reports indicated that the pathogen could potentially pose a threat to cruciferous crops, therefore, highlighting a need to conduct a state-wide survey for pectinolytic bacteria, and implement better management strategies to combat the vegetable crop losses.

Purpose: In September 2019, a rapidly spreading soft rot disease was observed in an Aloe vera cultivation in Puttlam District, Sri Lanka causing rotting of leaves and whole plant death, within three to five days. Identification of causal pathogen of soft rot was the main objective for effective management of the disease. The aim of this study was to isolate and molecular identification of causal pathogen of soft rot disease of A. vera and to confirm its pathogenicity. Research Method: The causal bacterium was isolated on Nutrient Agar medium and initially identified by colony characters. Pathogenicity was assessed by inoculation of leaves of potted A. vera plants with bacterial suspension of each isolates (x108 cfu ml-1). Bacterial DNA was extracted and subjected to PCR, using universal primers 27F and 1492R to amplify 16S rRNA region of the bacterium. The PCR products were sequenced and homology search was performed with GenBank database. Findings: Typical field symptoms began appearing after 24 hrs on inoculated plants, with the death of whole plant within two-three days after inoculation Based on PCR analysis, sequencing and homology search results, the causal pathogen of the bacterial soft rot disease of A. vera was identified as Dickeya chrysanthemi (former E. chrysanthemi). Sequences were deposited in GenBank for two bacterial isolates, kb (Accession No.MT028490.1) and kd (Accession No.MT028539.1). A BLAST search revealed 99 % identity with D. chrysanthemi from China (JF779681.1). Originality/Value: To our knowledge, this is the first report of D. chrysanthemi causing bacterial soft rot of A. vera in Sri Lanka. This finding will be very useful to formulating disease management strategies for bacterial soft rot of A. vera and to prevent outbreak of the disease.

Potato soft rot is one of the major destructive diseases affecting potato plants throughout the world. In a survey of different potato growing seasons in different regions of Jordan, samples of rotten potato tubers were collected and 131 isolates identified biochemically as Pectobacterium carotovorum subsp. carotovorum (Pcc). The PCR primer pair (EXPCCR/EXPCCF) was used to detect these Jordanian isolates. The primer set amplified a single fragment of 550 bp in size from the total genomic DNA, which was extracted independently from 67 Pcc strains. In a nested PCR, the primer set (INPCCR/INPCCF) amplified the expected single fragment of 400 bp from the PCR product of first PCR amplification. The use of these primers was not reliable in detecting all isolates identified biochemically as Pcc. Different rots causal agents were detected by PCR amplification and further sequenced. The sequencing data revealed similarities to different genera; Pseudomonas, Enterobacteriaceae genera such as Enterobacter spp., Serratia spp. and Klebsiella spp., in addition to P. carotovorum subsp. carotovorum. So far this is the first study where Pcc has been identified by using PCR and sequencing approaches in Jordan. Key words: Pectobacterium carotovorum subsp. carotovorum, specific primers, nested PCR, sequencing.

Tomato (Solanum lycopersicum L.) is a species of the family Solanaceae. It is herbaceous, annual to perennial, prostrate and sexually propagated plant with bisexual flower. Tomatoes are attacked by many kinds of plant pathogens such as fungi, bacteria, nematodes, viruses and viroid. Among bacterial diseases, bacterial soft rot devastates many important crops of the family Solanaceae particularly potato, eggplant and tomato, causing a huge decrease in yield and a greater loss in produce than any bacterial disease known. Yield losses due to post-harvest diseases of fruits and vegetables range from 20 to 30% but losses due to soft rot bacteria may reach up to 100% under insufficient conditions of storage facility, this have huge impacts on famers and vendors. In vitro efficacy of certain botanicals against bacterial soft rot of tomato were tested in the months of February to March, 2015 in the Department of Plant Pathology and Department of Biochemistry, Sam Higginbottom Institute of Agriculture, Technology and Sciences (Deemed University)– Allahabad, UP, India. Eight botanicals were screened in vitro, out of these, four were selected based on their performances and evaluated against the bacterial soft rot of storage tomato at 2, 4, and 8 days after inoculation. Maximum zone of inhibition was obtained with treated Control (T0b=17 mm), followed by Turmeric 30% (T4=12.4 mm), Turmeric 20% (T3=11 mm), then Neem 30% (T6) while the least zone of inhibition was recorded with untreated Control/water (T0a=0.4 mm) followed by Lemon 30% (T12=1 mm). Turmeric 30% (T4) proved to be best botanical under screening followed by Turmeric 20% (T3=11mm). In case of mean disease intensity at eight days after inoculation on storage tomato, highest mean value was recorded in Ginger 30% (T2=46.2) followed by Neem 20% (T5=44.2) and lowest value in Streptomycin (T0b=27), followed by Turmeric 20% (T3=27.6) then Turmeric 30% (T4=27.8). Among the botanicals, the lowest disease intensity was with T3=27.6 followed by T4= 27.8. Key words: Tomato, Pectobacterium carotovora subsp carotovora, botanicals, efficacy.

The genus Ornithogalum includes several ornamental species that suffer substantial losses from bacterial soft rot caused by Pectobacteria. The absence of effective control measures for use against soft rot bacteria led to the initiation of a project in which a small antimicrobial peptide from an Asian horseshoe crab, tachyplesin (tpnI), was introduced into two commercial cultivars: O. dubium and O. thyrsoides. Disease severity and bacterial colonization were examined in transgenic lines expressing this peptide. Disease resistance was evaluated in six lines of each species by measuring bacterial proliferation in the plant tissue. Three transgenic lines of each species were subjected to further analysis in which the expression level of the transgene was evaluated using RT-PCR and qRT-PCR. The development of disease symptoms and bacterial colonization of the plant tissue were also examined using GFP-expressing strain of P. carotovorum subsp. brasiliense Pcb3. Confocal-microscopy imaging revealed significantly reduced quantities of bacterial cells in the transgenic plant lines that had been challenged with the bacterium. The results clearly demonstrate that tpnI expression reduces bacterial proliferation, colonization and disease symptom (reduced by 95-100%) in the transgenic plant tissues. The quantity of tpnI transcripts, as measured by qRT-PCR, was negatively correlated with the protection afforded to the plants, as measured by the reduced severity of disease symptoms in the tissue.