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Background: Fire blight, caused by Erwinia amylovora, is the most destructive bacterial disease affecting plants in the Rosaceae family, leading to significant economic losses. In Algeria, this disease has been reported since 2010. This study aimed to investigate the origin of fire blight in Algeria, in order to increase knowledge of the epidemiology of this serious disease and contribute to its management. A comprehensive characterization of 18 E. amylovora isolates recovered from northern Algeria between 2016 and 2021 to evaluate their phenotypical and genotypical diversity was conducted. Results: Phenotypic differences, particularly in growth kinetics, virulence, and fatty acid profiles, allowed differentiation of strains into five groups, possibly indicating distinct introduction events. Genetic characterization revealed that only one strain lacked the ubiquitous plasmid pEA29, which is correlated with reduced virulence, while none harbored the pEI70 plasmid. Phylogenetic analysis using concatenated sequences of the recA, groEL, rpoS, ams, and hrpN genes grouped Algerian strains with those from a broadly prevalent clade. CRISPR genotyping identified a novel CR1 pattern and three genotypes, two of them previously unreported. Conclusions: This study represents the first phenotypic, genetic, and phylogenetic investigation of E. amylovora strains in the region, and provides valuable information on the possible pathways of the introduction of this fire blight pathogen in northern Africa. The findings suggest one or more introduction events from a common ancestor, likely originating in northern Italy, followed by dispersal in various regions of Algeria. [ABSTRACT FROM AUTHOR]

Erwinia amylovora, the causative agent of fire blight, causes significant economic losses for farmers worldwide by inflicting severe damage to the production and quality of plants in the Rosaceae family. Historically, fire blight control has primarily relied on the application of copper compounds and antibiotics, such as streptomycin. However, the emergence of antibiotic-resistant strains and growing environmental concerns have highlighted the need for alternative control methods. Recently, there has been a growing interest in adopting bacteriophages (phages) as a biological control strategy. Phages have demonstrated efficacy against the bacterial plant pathogen E. amylovora, including strains that have developed antibiotic resistance. The advantages of phage therapy includes its minimal impact on microbial community equilibrium, the lack of a detrimental impact on plants and beneficial microorganisms, and its capacity to eradicate drug-resistant bacteria. This review addresses recent advances in the isolation and characterization of E. amylovora phages, including their morphology, host range, lysis exertion, genomic characterization, and lysis mechanisms. Furthermore, this review evaluates the environmental tolerance of E. amylovora phages. Despite their potential, E. amylovora phages face certain challenges in practical applications, including stability issues and the risk of lysogenic conversion. This comprehensive review examines the latest developments in the application of phages for controlling fire blight and highlights the potential of E. amylovora phages in plant protection strategies. [ABSTRACT FROM AUTHOR]

Erwinia amylovora bacteriophages are of interest as fire blight control agents. This paper presents data on the biology and molecular genetic properties of 12 E. amylovora tailed bacteriophages. Genome sequences of seven of them were determined and the phages were identified as the representatives of Caudoviricetes; Vequintavirinae, Ounavirinae and Autographiviridae families. The bacteriophages studied were active against E. amylovora, Pantoea agglomerans and Pantoea ananatis strains. The myovirus Hena1 had the narrowest host range lysing 12% of the bacterial cultures tested, the remaining myoviruses—had broader host ranges (56%) for this collection. The phages showed different reactions to the presence of a chelating agent in the cultivation medium. A significant proportion of phage-resistant E. amylovora cells were found both in infected liquid cultures and in the experiments on the plates with the phage agar (more than 20% in case of exposure to podoviruses), which correlates with the data of limited number of previous investigations of the phenomenon for E. amylovora interactions with phages. High prevalence of resistant cells in the host cultures suggest that they are formed not due to spontaneous mutations but result from another phenotypic or genetic dissociation mechanism(s) that remains to be identified. [ABSTRACT FROM AUTHOR]

The apple is a significant global fruit cultivated extensively worldwide. Fire blight, caused by Erwinia amylovora (Ea), poses a significant threat to global apple production. To control this disease, characterizing the virulence mechanisms/factors is imperative. Carbamoyl phosphate synthase is an essential enzyme in the biosynthesis of arginine and pyrimidine. However, the functions of this protein in Ea remains poorly understood. This study aimed to investigate the functions of the carbamoyl phosphate synthase large subunit in Ea (CarBEa). In a virulence assay using fruitlets, an Ea strain lacking CarBEa exhibited significantly reduced virulence on fruitlets. In the auxotrophy assay, this mutant failed to grow in minimal media lacking both arginine and pyrimidine, but growth was restored when both compounds were supplemented. The comparative proteomic analysis suggests that CarBEa is involved in diverse biological processes, including amino acid and nucleotide metabolism, and inorganic ion transport. Finally, we demonstrated that CarBEa is related to siderophore secretion/production by the chrome azurol S agar plate assay. This report provides valuable insights into the functions of carbamoyl phosphate synthase large subunit, which serves as a potential target for developing efficient anti-virulence substances to control fire blight. [ABSTRACT FROM AUTHOR]

In the present study, the most valuable cultivar 'Aport krovavo-krasnyy' was grafted onto M. sieversii genotypes harvested from 11 populations in Dzungarian Alatau and Ile Alatau to identify ones resistant to Erwinia amylovora. The wild apple populations included in the present research have not been previously explored. Seedling population 10, developed using rootstocks from a M. sieversii population growing in Turgen, demonstrated the highest resistance to Erwinia amylovora, showing no fire blight symptoms and no positive PCR results for E. amylovora during the eight years of monitoring in the Talgar field (Kazakhstan) from 2015 to 2022. The population from Steep Tract (seedling population 1) was also valuable for breeding and reduced the pathogen distribution to below 30%. Genotypes from a genetic reserve (seedling population 5) were the most susceptible among the researched populations, with a disease distribution level of 24–95%. In seedling population 5, trees affected at least twice by the pathogen exhibited wilting, shepherd's crook formation, leaf necrosis, and occasional exudate droplets, while trees in other combinations primarily showed shoot wilting and leaf death. Fire blight disease also developed more rapidly within the plant in seedling population 5; by 2020, one tree nearly died after only two infections. [ABSTRACT FROM AUTHOR]

Summary: Changes in the plant microbiota composition are intimately associated with the health of the plant, but factors controlling the microbial community in flowers are poorly understood. In this study, we used apple flowers and fire blight as a model system to investigate the effects of floral microbiota and microbial competition on disease development and suppression.To compare changes in microbial flora with the RNA expression patterns of plants, the flower samples were collected in three different flowering stages (Bud, Popcorn, and Full‐bloom). Using advanced sequencing technology, we analyzed the data and conducted both in vitro and in vivo experiments to validate our findings.Our results show that the Erwinia amylovora use arabinogalactan, which is secreted on the flowers, for early colonization of apple flowers. Pantoea agglomerans was more competitive for arabinogalactan than E. amylovora. Additionally, P. agglomerans suppressed the expression of virulence factors of E. amylovora by using arabinose, which is a major component of arabinogalactan, which induces virulence gene expression.The present data provide new insights into developing control strategies for diverse plant diseases, including fire blight, by highlighting the importance of nutrients in disease development or suppression. [ABSTRACT FROM AUTHOR]

Agrochemicals containing antibiotics are authorized to manage fire blight that has been occurring in Korea since 2015. The minimum inhibitory concentration (MIC) of each antibiotic against Erwinia amylovora, the causal pathogen of fire blight, has increased over the years due to the pathogen’s frequent exposure to antibiotics, indicating the necessity to prepare for the emergence of antibiotic resistance. In this study, E. amylovora was exposed to stepwise increasing concentrations of eight different agrochemicals, each containing single or mixed antibiotics, and gene mutation and changes in MIC were assessed. Streptomycin and oxolinic acid induced an amino acid substitution in RpsL and GyrA, respectively, resulting in a rapid increase in MIC. Oxytetracycline initially induced amino acid substitutions or frameshifts in AcrR, followed by substitutions of 30S small ribosomal protein subunit S10 or AcrB, further increasing MIC. E. amylovora acquired resistance in the order of oxolinic acid, streptomycin, and oxytetracycline at varying exposure frequencies. Resistance acquisition was slower against agrochemicals containing mixed antibiotics than those with single antibiotics. However, gene mutations conferring antibiotic resistance emerged sequentially to both antibiotics in the mixed formulations. Results suggested that frequent application of mixed antibiotics could lead to the emergence of multidrug-resistant E. amylovora isolates. This study provided essential insights into preventing the emergence of antibiotic-resistant E. amylovora and understanding the underlying mechanisms of resistance acquisition.

Abstract Background Fire blight, caused by Erwinia amylovora, is the most destructive bacterial disease affecting plants in the Rosaceae family, leading to significant economic losses. In Algeria, this disease has been reported since 2010. This study aimed to investigate the origin of fire blight in Algeria, in order to increase knowledge of the epidemiology of this serious disease and contribute to its management. A comprehensive characterization of 18 E. amylovora isolates recovered from northern Algeria between 2016 and 2021 to evaluate their phenotypical and genotypical diversity was conducted. Results Phenotypic differences, particularly in growth kinetics, virulence, and fatty acid profiles, allowed differentiation of strains into five groups, possibly indicating distinct introduction events. Genetic characterization revealed that only one strain lacked the ubiquitous plasmid pEA29, which is correlated with reduced virulence, while none harbored the pEI70 plasmid. Phylogenetic analysis using concatenated sequences of the recA, groEL, rpoS, ams, and hrpN genes grouped Algerian strains with those from a broadly prevalent clade. CRISPR genotyping identified a novel CR1 pattern and three genotypes, two of them previously unreported. Conclusions This study represents the first phenotypic, genetic, and phylogenetic investigation of E. amylovora strains in the region, and provides valuable information on the possible pathways of the introduction of this fire blight pathogen in northern Africa. The findings suggest one or more introduction events from a common ancestor, likely originating in northern Italy, followed by dispersal in various regions of Algeria.

Polymerase chain reaction (PCR) methods, including conventional PCR (cPCR) and quantitative real-time PCR (qRT-PCR), with both plasmid- and chromosome-targeting primers, are currently the most reliable methods for detecting Erwinia amylovora due to their high sensitivity and specificity. Despite qRT-PCR's quantitative advantage, cPCR remains an attractive method to detect this bacterium in initial screenings of suspected host plants, as it is cost-effective and does not require skilled personnel in well-equipped laboratories. This study aimed to significantly improve cPCR robustness via application of bovine serum albumin (BSA) as a PCR facilitator, with a modified EaF/R primer pair, as previously reported. Experiments have shown that simple supplementation with BSA (10 mg/ml) enhances cPCR reactions using templates such as genomic DNA, bacterial cells, and infected symptomless host organs, including immature apple fruits and seedlings, with EaF/R primers. The cPCR method described in this study is simple, specific, and reliable, and can be applied in routine assays to diagnose fire blight.

Since its initial outbreak in Korea in 2015, fire blight has consistently emerged annually. Fire blight out-breaks usually begin in May, peak in June, and decline in July in Korea. In this study, we analyzed cases that exhibit a distinct pattern of disease occurrence based on yearly weather conditions from 2020 to 2023. In 2020, fire bight disease occurrence began in late May. Although the disease incidence started late by the low temperatures in April, which caused flowering period delayed, the incidence increased significantly due to the high risk of blossom infection. In 2021, the first outbreak began in late April because the flower infection started in early April. In 2022, despite the high blossom infection risk during the flowering period in April and the high incidence of fire blight in May, the incidence decreased sharply from June due to the low rainfall in May. In 2023, due to torrential rains and hail in late June, the incidence of fire blight increased even in July. Considering the weather factors that affect the increase of fire blight disease, it is suggested that control measures to prevent the fire blight infection should be carried out before and after wind-driven rains.

The bacterium Erwinia amylovora is one of the most important pathogens of apples, causing significant damage. During the experimental years, 2021 and 2022, both the temperature and humidity in summer months, were favourable for the occurrence of fire blight in areas with a temperate climate. The absence of major genes for resistance to fire blight makes it difficult to improve apple cultivars in terms of this characteristic. Therefore, studies regarding the behaviour of apple cultivars, in certain environmental conditions, have kept their relevance. The behaviour of the cultivars studied was compared with that of ‘Auriu de Bistrița’, previously known to be susceptible to fire blight. Ten of the twelve cultivars performed well in 2021 and 2022 The results showed that ‘Jonaprim’ was not affected by Erwinia amylovora while other Romanian or foreign cultivars were sporadically affected. ‘Auriu de Bistrița’ presented a higher frequency of specific symptoms, than all the other cultivars.

Pathogens of fire blight can survive for a long time on pruning tools, etc., and fire blight can be spread through agricultural implements. In particular, in Korea, pruning is frequently performed to remove flowers, immature fruits, and succulent shoots, and this farm work is known to be a major factor of the spread of fire blight. Therefore, in this study, in order to completely sterilize pathogens on pruning shears, we verified the disinfection effect of disinfectants distributed domestically and used them to identify an effective disinfection method. When disinfecting by immersion after inoculating Erwinia amylovora TS3128 on the scissor blade, 70% ethanol and 1% and 0.2% sodium hypochlorite sterilized immediately 10 sec after immersion, while 30% chlorine dioxide showed little disinfection effect. When disinfecting by spraying, 70% ethanol sterilized bacteria 1 sec after spraying, but 1% and 0.2% sodium hypochlorite disinfected bacteria after 10 and 60 sec, respectively. After cutting the naturally disease occurring branches five and 100 times, the bacteria were not hardly sterilized in immersion treatment in 70% ethanol for 30 sec but perfectly disinfected over 60 sec. Considering these results, pruning shears should be disinfected by frequently immersing them in 70% ethanol for at least 60 sec during pruning work in the field.

Erwinia amylovora, a causal pathogen of fire blight, has been continuously inducing damage to the apple and pear trees in South Korea since 2015. Farmers apply antibiotics during blooming season to prevent the fire blight. However, continuous use of antibiotics can induce the emergence of resistant bacteria, which consequently reduces control efficacy. In this study, we assessed the minimal inhibitory concentration (MIC) of streptomycin, using a total of 361 E. amylovora isolates that were collected from the six provinces of South Korea from 2019 to 2023. As a result, the MIC of streptomycin ranged from 0.5 to 4 µg/ml and the strA-strB genes were not identified from the isolates. The MIC was higher in the isolates from Gyeonggi-do, Gangwon-do, and Chungcheongbuk-do compared to those from other three provinces. These results may bring broad attention to the use of streptomycin and aid in developing a management protocol for the occurrence of fire blight in South Korea.

K-Maryblyt has been developed for the effective control of secondary fire blight infections on blossoms and the elimination of primary inoculum sources from cankers and newly emerged shoots early in the season for both apple and pear trees. This model facilitates the precise determination of the blossom infection timing and identification of primary inoculum sources, akin to Maryblyt, predicting flower infections and the appearance of symptoms on various plant parts, including cankers, blossoms, and shoots. Nevertheless, K-Maryblyt has undergone significant improvements: Integration of Phenology Models for both apple and pear trees, Adoption of observed or predicted hourly temperatures for Epiphytic Infection Potential (EIP) calculation, incorporation of adjusted equations resulting in reduced mean error with 10.08 degree-hours (DH) for apple and 9.28 DH for pear, introduction of a relative humidity variable for pear EIP calculation, and adaptation of modified degree-day calculation methods for expected symptoms. Since the transition to a model-based control policy in 2022, the system has disseminated 158,440 messages related to blossom control and symptom prediction to farmers and professional managers in its inaugural year. Furthermore, the system has been refined to include control messages that account for the mechanism of action of pesticides distributed to farmers in specific counties, considering flower opening conditions and weather suitability for spraying. Operating as a pivotal module within the Fire Blight Forecasting Information System (FBcastS), K-Maryblyt plays a crucial role in providing essential fire blight information to farmers, professional managers, and policymakers.

FB_MR5 is a nucleotide-binding domain and leucine-rich repeat protein identified from wild apple species Malus × robusta 5 conferring disease resistance to bacterial fire blight. FB_MR5 (hereafter MrMR5) recognizes the cysteine protease effector EaAvrRpt2 secreted from the causal agent of bacterial fire blight, Erwinia amylovora. We previously reported that MrMR5 is activated by the C-terminal cleavage product (ACP3) of Malus domestica RIN4 (MdRIN4) produced by EaAvrRpt2- directed proteolysis. We show that MbMR5 from a wild apple species Malus baccata shares 99.4% amino acid sequence identity with MrMR5. Surprisingly, transient expression of MbMR5 in Nicotiana benthamiana showed autoactivity in contrast to MrMR5. Domain swap and mutational analyses revealed that 1 amino acid polymorphism in the MbMR5 CC domain is critical in enhancing autoactivity. We further demonstrated that MrMR5 carrying 7 amino acid polymorphisms present in MbMR5 is not activated by MdRIN4 ACP3 but recognizes AvrRpt2 without MdRIN4 in N. benthamiana. Our findings indicate that naturally occurring polymorphisms of MR5 natural variants can confer its cell death-inducing activity and the effector recognition mechanism likely due to altered compatibility with RIN4. [ABSTRACT FROM AUTHOR]

Fire blight is a devastating disease of apple and pear worldwide. One reason fire blight is so difficult to manage is because of the lack of effective non-antibiotic management options as well as a limited host resistance gene pool. Traditional management approaches utilizing antibiotic and copper sprays face multiple problems including antibiotic resistance and human health concerns. Furthermore, most management materials are used to control the blossom blight stage of infection, and fewer materials are available to control shoot blight stage of infection. Breeding for host resistance against fire blight is limited by the heterozygosity of apple, as well as the lack of understanding of the host-pathogen interactions. In this review, we raised some of these "burning questions", which suggest directions for future research in management and resistance breeding of fire blight. [ABSTRACT FROM AUTHOR]

Aureobasidium pullulans, formulated commercially as Blossom Protect, has become a highly successful biological material for fire blight suppression in apple and pear. This material, which is composed of viable spores of two strains of A. pullulans, attained this status with minimal prior knowledge that yeasts could be used effectively for this purpose. In early orchard trials, it was observed that mixing A. pullulans in spray tanks with a low pH buffer enhanced disease suppression from very good to outstanding. Prevention of fire blight by Blossom Protect requires that A. pullulans colonizes most of the flowers on a tree with populations that exceed 1 × 104 CFU/flower. A. pullulans colonizes floral stigmas similar to bacteria used to suppress fire blight biologically; however, unlike these bacteria, the yeast also colonizes the hypanthial surface within the floral cup, which is where the fire blight pathogen Erwinia amylovora infects the host. In combination with the buffer, colonization activity by A. pullulans on the hypanthium reduces pH of the floral cup and strongly induces host defense genes in hypanthial tissue. A specific risk from use of A. pullulans for fire blight control is a potential to contribute to 'russeting' of developing fruitlets. Russeting risk from use of Blossom Protect has been lessened by reformulation of the companion buffer and by use of conventional or organically-approved fungicides in late and post-bloom periods. In large-scale apple production, particularly organic orchards, the use of Blossom Protect requires integration with other sprays that are required for managing crop load and suppression of fungal diseases such as apple scab. [ABSTRACT FROM AUTHOR]

Erwinia amylovora, the causative agent of fire blight of pome fruits and other rosaceous plants belongs to the group of regulated quarantine pests. The aim of this work was to characterize the populations of E. amylovora in Norway and their geographical distribution. A total of 238 E. amylovora isolates recovered from symptomatic host plants in Norway between 1986 and 2004 were genotyped by means of a short sequence repeat (SSR) marker (ATTACAGA) on plasmid pEa29. The SSR region was amplified and amplicon size determined using fluorescent labelling and rapid, automated capillary gel electrophoresis. All isolates contained the pEa29 plasmid harbouring the investigated marker. In total, ten genotypes were identified, of which two were detected only once. The number of repeats varied from 3 to 13, with 43% of the isolates containing five repeats. Of 17 isolates collected between 1986 and 1991, all but one contained five repeats, whereas more variation was observed in isolates from the period 2000 to 2004. Most of the isolates (80%) originated from Cotoneaster bullatus, hence no relationship between genotype of the isolate and host species that it was isolated from could be detected. This historic data suggests multiple introductions of E. amylovora to Norway. [ABSTRACT FROM AUTHOR]

Fire blight, caused by Erwinia amylovora, can be spread through orchards and nurseries because of poor sanitation practices such as contaminated secateurs. This research investigated the efficacy of 12 commercial sterilants at varying concentrations to kill E. amylovora on secateurs. Secateurs were dipped into an Erwinia amylovora inoculum solution (106 colony forming units/mL), and then misted with a test sterilant. After 10 s, secateurs were swabbed and plated onto Kings B agar plate, incubated at 26 °C for 48 h and bacterial colonies counted. Sterilants were also assessed for cotton bleaching and metal corrosion. Best performing sterilants were then tested as described above by cutting through infected plant material containing sticky bacterial ooze as inoculum. Each of the sterilants tested (methylated spirits (95% and 70%), sodium hypochlorite (NaOCl) (1%, 0.5%, 0.135%), Bac-Stop/benzalkonium chloride (2%, 1%), Virkon™ (label rate), Dettol (50%, 10%, 1%, 0.1%), and HarvestCide® gel (0.1%, 0.5%, 1%)) were found to be effective to kill E. amylovora on inoculum-coated secateurs. The best performing sterilants (methylated spirits, Dettol, HarvestCide gel, NaOCl) were also effective in killing E. amylovora on infected plant material when compared with the untreated control. Most sterilants, except methylated spirits or Dettol, caused corrosion of metal and bleaching of cotton. Each of the tested sterilants were found to be effective to kill Erwinia amylovora on inoculum-coated secateurs and inoculum in plant material and bacterial ooze. Many of the best performing sterilants were likely to damage tools over time and cause bleaching on clothing. However, Dettol or methylated spirits did not cause metal corrosion or bleaching. [ABSTRACT FROM AUTHOR]

With increasing organic acreage and scrutiny of antibiotics use, alternatives to antibiotics for the control of Erwinia amylovora are of interest to stakeholders. At the same time failures of minimally tested, newly marketed products have resulted in severe infections leading to costly tree and orchard removal. We evaluated antibiotic alternatives in 8 Washington, 3 Oregon, 3 New York and 2 Pennsylvania field experiments conducted 2013 to 2022. Antibiotic alternatives included essential oils (thyme and cinnamon extracts), mineral compounds (potassium aluminum sulfate), oxidizers (peracetic acid-peroxide), soluble coppers (copper octanoate, copper hydroxide, copper sulfate pentahydrate), and biological controls (Aureobasidium pullulans, Bacillus subtilis, bacteriophage). Studies were conducted in 'Bartlett' and 'dAnjou' pear, 'Gala', 'Cameo,' and 'Red Delicious' apple with 4 to 6 single-tree replicates arranged in a randomized complete block inoculated with E. amylovora at 80–100% bloom. In summary analysis of 8 Washington trials Alum (potassium aluminum sulfate), Blossom Protect (A. pullulans) and several copper products (Previsto, Mastercop, Instill) provided good disease suppression of 70–73% similar to antibiotic checks. Several essential oil, copper, and peracetic acid-peroxide and biological products (Serenade Opti, Cueva, Oxidate 5.0, Jet Ag, Thyme Guard and Thymox) provided intermediate disease suppression between 45 and 62% significantly better than the water-treated control. In multistate trials Alum with 2–3 applications provided good control in most experiments (means 2019: WA 79%, NY 77%, PA 57%; 2020: OR 86%, NY 65%, WA 28%; 2021: NY 87%, WA 50%). Essential oils with 3–4 applications provided intermediate control NY 2021 81% control 23% thyme oil, 70–85% control NY 2020, 2021 60% cinnamon oil. [ABSTRACT FROM AUTHOR]

Bacteriophages offer unique benefits for the specific control of Erwinia amylovora, the causative agent of fire blight in pome fruit. Unfortunately, the majority of described phages were tested for efficacy in vitro only. Data from infection assays using pear slices or detached blossoms is rare and field trials are barely reported. It remains to be studied if bacteriophages could control fire blight in the open field. This review summarizes current knowledge of different phages infecting E. amylovora. In addition, the requirements for a phage to optimally function as a biological antimicrobial agent in agriculture are discussed together with the ideal setup of field trials and the formulation of phages for best results. [ABSTRACT FROM AUTHOR]

The effects of mineral composition (N, P, K, Mg, Fe, Cu, and Zn) against fire blight caused by Erwinia amylovora, the most devastating disease of pome fruits, was investigated in pear. Due to the transport physiology of minerals, the leaf contained higher concentrations of every mineral analyzed, especially macro-minerals (N, P, K, and Mg) compared to the fruit. Minerals obtained from the leaves were not statistically correlated with resistance to fire blight, however all the minerals examined in the fruit, except for K, were found to be significant. Increased P and Mg concentrations were associated with disease resistance, while N, Zn, Fe, and Cu were associated with susceptibility. Nitrogen-causing susceptibility exerted 61% of this impact through itself directly and was sharply distinguished from other mineral compounds. Furthermore, the indirect effect of nitrogen on disease susceptibility through Cu (39%), Zn (33%), and Fe (30%) was even higher than the direct effect of these minerals (21%, 24%, and 29%, respectively). The direct effects of P (13%) and Mg (10%), which are associated with an increase in resistance, were lower than the indirect effects (19% and 29%, respectively) due to their negative correlation with nitrogen, showing that the main effect of these minerals was in suppressing the negative effects of nitrogen on susceptibility by maintaining mineral balance. [ABSTRACT FROM AUTHOR]

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Bacteriophages have emerged as effective antimicrobial agents in combating pathogenic bacteria. To successfully apply phages in real‐life scenarios, it is crucial to optimize their large‐scale production, concentration and purification processes. In this study, our objective was to optimize the phage concentration parameters with a high recovery rate within a shorter time and minimum chemical consumption. We isolated and characterized a specific Erwinia amylovora phage. Subsequently, we employed response surface methodology (RSM) combined with a three‐factor central composite design to optimize the phage recovery. The factors considered were polyethylene glycol (PEG) concentration, NaCl concentration and incubation time. The optimized values for PEG, NaCl and incubation time, which resulted in a maximum recovery rate of 85.37%, were determined as 18%, 2.38 M and 0 h, respectively. This finding indicates that the concentration step, which traditionally took up to 18 h with a recovery rate of 65%, can now be accomplished in a significantly shorter time with an improved recovery rate. Our study demonstrates the effectiveness of RSM to identify the optimum conditions for phage precipitation. This approach allows for the rapid and efficient design of precipitation protocols tailored to specific bacteriophages, resulting in shorter processing times and higher recovery rates. [ABSTRACT FROM AUTHOR]

The need for the increasing geographical spread of fire blight (FB) affecting fruit crops to be addressed led to large-scale chemicalization of the environmental matrices and reduction of plant productivity. The current study aimed to assess the effects of novel biopreparations at different exposure durations on photosynthetic pigment content and antioxidant enzyme activity in leaves of apple and pear varieties with varying levels of resistance to FB. Biopreparations were formulated from a cultural broth containing Lacticaseibacillus paracasei M12 or Bacillus amyloliquefaciens MB40 isolated from apple trees' phyllosphere. Aseptic leaves from blight-resistant (endemic Malus sieversii cv. KG10), moderately resistant (Pyrus pyraster cv. Wild), and susceptible (endangered Malus domestica cv. Aport and Pyrus communis cv. Shygys) varieties were employed. The impact of biopreparations on fruit crop antioxidant systems and photosynthetic apparatuses was investigated in vitro. Study results indicated that FB-resistant varieties exhibit enhanced adaptability and oxidative stress resistance compared to susceptible ones. Plant response to biopreparations varied based on the plant's initial FB sensitivity and exposure duration. Indeed, biopreparations improved the adaptive response of the assimilation apparatus, protein synthesis, and catalase and superoxide dismutase activity in susceptible varieties, suggesting that biopreparations have the potential for future commercialization to manage FB in fruit crops. [ABSTRACT FROM AUTHOR]

This article explores the role of the WAK3 gene in Arabidopsis plants' immune responses to harpins, proteins produced by certain bacteria that activate plant defenses. The researchers used T-DNA insertion mutants to study WAK3 and found that it is essential for the necrosis and acquired resistance responses triggered by harpins. They also discovered that genetic variation in harpin perception may impact plant fitness. The study benefited from the use of the 1001 Genomes data, which eliminated the need for lengthy genetic mapping. This research provides valuable insights into the genetic basis of plant immune responses and its potential implications for crop protection. [Extracted from the article]

Fire blight, caused by the Gram-negative bacterium Erwinia amylovora, poses a substantial threat to pome fruit production worldwide. Despite existing control strategies, a pressing need remains for sustainable and environmentally friendly fire blight management. Myxobacteria, renowned for their predatory behavior and potent enzymes, emerge as a groundbreaking biocontrol approach with significant potential. Here, we report the biocontrol potential of a novel Myxococcus fulvus WCH05, against E. amylovora. Using various in vitro and planta assays, we demonstrated the multifaceted biocontrol abilities of strain WCH05. In plate predation assays, strain WCH05 exhibited not only strong predation against E. amylovora but also broad-spectrum activities against other plant pathogenic bacteria. Pre-treatment with strain WCH05 significantly decreased pear blossom blight incidence in detached inflorescence assays, achieving a controlled efficacy of 76.02% that rivaled the antibiotic streptomycin (79.79%). In greenhouse trials, strain WCH05 effectively reduced the wilting rate and disease index in young pear seedlings, exhibiting both protective (73.68%) and curative (68.66%) control. Further investigation revealed that the biocontrol activity of strain WCH05 relies on both direct contact and extracellular enzyme secretion. While cell extracts lacked inhibitory activity, ammonium sulfate-precipitated secreted proteins displayed potent lytic activity against E. amylovora. Substrate spectrum analysis identified peptidases, lipases, and glycosidases among the secreted enzymes, suggesting their potential roles in pathogen degradation and biocontrol efficacy. This study presents the first evidence of Myxococcus fulvus WCH05 as a biocontrol agent against fire blight. Its potent predatory abilities and enzymatic arsenal highlight its potential for sustainable disease management in pome fruit production. Future research will focus on identifying and characterizing specific lytic enzymes and optimizing strain WCH05 application strategies for field efficacy. [ABSTRACT FROM AUTHOR]

Fire blight, caused by the bacterium Erwinia amylovora, is a major threat to pear production worldwide. Bacteriophages, viruses that infect bacteria, are a promising alternative to antibiotics for controlling fire blight. In this study, we isolated a novel bacteriophage, RH-42-1, from Xinjiang, China. We characterized its biological properties, including host range, plaque morphology, infection dynamics, stability, and sensitivity to various chemicals. RH-42-1 infected several E. amylovora strains but not all. It produced clear, uniform plaques and exhibited optimal infectivity at a multiplicity of infection (MOI) of 1, reaching a high titer of 9.6 × 109 plaque-forming units (PFU)/mL. The bacteriophage had a short latent period (10 min), a burst size of 207 PFU/cell, and followed a sigmoidal one-step growth curve. It was stable at temperatures up to 60 °C but declined rapidly at higher temperatures. RH-42-1 remained viable within a pH range of 5 to 9 and was sensitive to extreme pH values. The bacteriophage demonstrates sustained activity upon exposure to ultraviolet radiation for 60 min, albeit with a marginal reduction. In our assays, it exhibited a certain level of resistance to 5% chloroform (CHCl3), 5% isopropanol (C3H8O), and 3% hydrogen peroxide (H2O2), which had little effect on its activity, whereas it showed sensitivity to 75% ethanol (C2H5OH). Electron microscopy revealed that RH-42-1 has a tadpole-shaped morphology. Its genome size is 14,942 bp with a GC content of 48.19%. Based on these characteristics, RH-42-1 was identified as a member of the Tectiviridae family, Alphatectivirus genus. This is the first report of a bacteriophage in this genus with activity against E. amylovora. [ABSTRACT FROM AUTHOR]

Persister cell and viable but non-culturable (VBNC) state of bacteria are survival strategies against antibiotics and various environmental stresses, respectively, but they tend to be ignored in agriculture fields, even though bacteria can regain their abilities to survive and produce disease once those stresses disappear. This study was carried out to determine whether persister cell and VBNC state in Erwinia amylovora are present after exposures to streptomycin, the length of their persistence, and the steps needed to decrease the inoculum. Persister cells were observed using biphasic killed growth curve for 4--8 h when the late stationary phase cells of E. amylovora were cultured in liquid medium containing streptomycin. This state was maintained for up to 12 h based on the colony forming units (CFUs) of the colonies that grew on the mannitol glutamate yeast extract (MGY) medium after streptomycin was removed. The CFUs on the MGY medium were lower than the total count determined using the LIVE/DEAD Kit, suggesting that persister cells and VBNC state might co-exist for up to 12 h after exposure to streptomycin. However, after 12 h, E. amylovora cells did not continue to grow on the medium for 9 days, suggesting that they entered a VBNC state at that time and remained in a persistent state. In addition, based on the Redox Sensor Green staining method, the presence of both states was confirmed for up to 12 h, and only then did the VBNC state became apparent. Furthermore, persister cells were observed for up to 24 h, and damaged cells reduced when E. amylovora cells were culture in distilled water with streptomycin, indicating that the uptake of lower nutrients in E. amylovora led to prolonged persister cells and VBNC state, which are more likely to survive after streptomycin treatments. The addition of sucrose and oxytetracycline to distilled water containing streptomycin reduced persister cells than other sources did. Thus, to inhibit the spread of fire blight, management techniques must consider the hazards of using streptomycin treatments that induce dormancy, such as persister cells and VBNC state, beyond the development of resistant strain. [ABSTRACT FROM AUTHOR]

Necrogenic Gram-negative bacterium Erwinia amylovora, which causes economic losses especially in pome fruits such as apple, pear, quince and loquat, some berries and many ornamental plants, causes fire blight disease. Copper compounds are used extensively in disease control programs and they can cause toxicproblems in terms of plant and environmental health. In addition, the formation of resistance to copper in the pathogen is frequently observed. In this study, plant activator phosphorous acid and biological control agent Bacillus subtilis, and 3 different copper compounds, Copper sulfate, Copper oxychloride and Copper hydroxide which are commonly used against E. amylovora, on apple cv. Gala with M9 rootstock were evaluated comparatively. When the new season shoot lengths of 3-year-old plants with homogeneous growth reached 20-25 cm, chemicals and B. subtilis were applied first time before one week ago from the pathogen inoculation, and after 2 times with 1 week intervals. The youngest two leaves at tips of actively growing terminal plant shoots were inoculated by cutting off using scissors dipped in suspension of E. amylovora str. EaARADY5 containing 108 CFU ml-1. Disease assessments were made after the disease severity (%) was determined on the basis of shoot blight after symptom development of the disease stopped, and the results were found to be statistically significant (p

Erwinia amylovora, the causative agent of fire blight, causes significant economic losses for farmers worldwide by inflicting severe damage to the production and quality of plants in the Rosaceae family. Historically, fire blight control has primarily relied on the application of copper compounds and antibiotics, such as streptomycin. However, the emergence of antibiotic-resistant strains and growing environmental concerns have highlighted the need for alternative control methods. Recently, there has been a growing interest in adopting bacteriophages (phages) as a biological control strategy. Phages have demonstrated efficacy against the bacterial plant pathogen E. amylovora, including strains that have developed antibiotic resistance. The advantages of phage therapy includes its minimal impact on microbial community equilibrium, the lack of a detrimental impact on plants and beneficial microorganisms, and its capacity to eradicate drug-resistant bacteria. This review addresses recent advances in the isolation and characterization of E. amylovora phages, including their morphology, host range, lysis exertion, genomic characterization, and lysis mechanisms. Furthermore, this review evaluates the environmental tolerance of E. amylovora phages. Despite their potential, E. amylovora phages face certain challenges in practical applications, including stability issues and the risk of lysogenic conversion. This comprehensive review examines the latest developments in the application of phages for controlling fire blight and highlights the potential of E. amylovora phages in plant protection strategies.

In the present study, the most valuable cultivar ‘Aport krovavo-krasnyy’ was grafted onto M. sieversii genotypes harvested from 11 populations in Dzungarian Alatau and Ile Alatau to identify ones resistant to Erwinia amylovora. The wild apple populations included in the present research have not been previously explored. Seedling population 10, developed using rootstocks from a M. sieversii population growing in Turgen, demonstrated the highest resistance to Erwinia amylovora, showing no fire blight symptoms and no positive PCR results for E. amylovora during the eight years of monitoring in the Talgar field (Kazakhstan) from 2015 to 2022. The population from Steep Tract (seedling population 1) was also valuable for breeding and reduced the pathogen distribution to below 30%. Genotypes from a genetic reserve (seedling population 5) were the most susceptible among the researched populations, with a disease distribution level of 24–95%. In seedling population 5, trees affected at least twice by the pathogen exhibited wilting, shepherd’s crook formation, leaf necrosis, and occasional exudate droplets, while trees in other combinations primarily showed shoot wilting and leaf death. Fire blight disease also developed more rapidly within the plant in seedling population 5; by 2020, one tree nearly died after only two infections.

The apple is a significant global fruit cultivated extensively worldwide. Fire blight, caused by Erwinia amylovora (Ea), poses a significant threat to global apple production. To control this disease, characterizing the virulence mechanisms/factors is imperative. Carbamoyl phosphate synthase is an essential enzyme in the biosynthesis of arginine and pyrimidine. However, the functions of this protein in Ea remains poorly understood. This study aimed to investigate the functions of the carbamoyl phosphate synthase large subunit in Ea (CarBEa). In a virulence assay using fruitlets, an Ea strain lacking CarBEa exhibited significantly reduced virulence on fruitlets. In the auxotrophy assay, this mutant failed to grow in minimal media lacking both arginine and pyrimidine, but growth was restored when both compounds were supplemented. The comparative proteomic analysis suggests that CarBEa is involved in diverse biological processes, including amino acid and nucleotide metabolism, and inorganic ion transport. Finally, we demonstrated that CarBEa is related to siderophore secretion/production by the chrome azurol S agar plate assay. This report provides valuable insights into the functions of carbamoyl phosphate synthase large subunit, which serves as a potential target for developing efficient anti-virulence substances to control fire blight.

Smilax aspera L. (commonly known as sarsaparilla) is recognized for its composition rich in flavonoids, phenylpropanoids, steroidal saponins, stilbenoids, and tannins, exhibiting anti-inflammatory, cytotoxic, and antimicrobial properties. This study investigates the hydromethanolic extracts of its leaves and fruits through vibrational spectroscopy and gas chromatography–mass spectrometry, evaluating their potential as biorationals for safeguarding crops. Analysis of S. aspera leaf and fruit extracts revealed the presence of phytochemicals such as lactones and other furan derivatives. In vitro assessments against three phytopathogens—Erwinia amylovora, Pseudomonas syringae pv. actinidiae, and Xanthomonas campestris pv. campestris—demonstrated strong antibacterial activity, with minimum inhibitory concentration (MIC) values of 1500 μg·mL−1 for both extracts. Biofilm tests indicated that the leaf extract reduced biofilm formation by 78–85%, while the fruit extract led to a reduction of 73–92.5%. At a concentration of 750 µg·mL−1, the extracts caused a decrease in amylovoran synthesis by 41–58%. Additionally, noticeable alterations in membrane permeability were observed at MIC and MIC/2 doses. Subsequent in vivo trials conducted on Pyrus communis L. trees utilizing the combined aerial part extract yielded substantial protection against E. amylovora at a dose of 1500 μg·mL−1, reaching 80% wilting reduction for the leaf extract. The findings presented herein cast S. aspera extracts as a promising natural-based treatment against these bacterial phytopathogens. [ABSTRACT FROM AUTHOR]

Considering the high level of risks that infection with the bacteria Erwinia amylovora has in apple orchards in Romania, we have undertaken a four consecutive years (2019-2022) investigation in terms of fire blight occurrence. In the experimental plots typical symptoms, such as wilted or necrotic shoots in the form of 'shepherd's crook, were visible for two consecutive years (2021-2022), while flower clusters were not affected. The highest damage degree was observed in 2022, when was recorded the least amount of precipitation in the May-June period, but accompanied by extreme phenomena, such as strong winds. At the same time, during the study, the average daily temperatures in the case of May were the highest in 2022, respectively the second highest, in the case of June, being exceeded only by June 2019. According to our observations, the climate changes in the area, which consist of both the increase of the average annual temperature and the occurrence of some extreme phenomena with greater frequency, are favoring factors to increase the occurrence of Erwinia amylovora and amplify the fire blight symptoms in apples. [ABSTRACT FROM AUTHOR]

Erwinia amylovora is a Gram-negative bacterium, responsible for the fire blight disease in Rosaceae plants. Its virulence is correlated with the production of an exopolysaccharide (EPS) called amylovoran, which protects the bacterium from the surrounding environment and helps its diffusion inside the host. Amylovoran biosynthesis relies on the expression of twelve genes clustered in the ams operon. One of these genes, amsI, encodes for a Low Molecular Weight Protein Tyrosine Phosphatase (LMW-PTP) called EaAmsI, which plays a key role in the regulation of the EPS production pathway. For this reason, EaAmsI was chosen in this work as a target for the development of new antibacterial agents against E. amylovora. To achieve this aim, a set of programs (DOCK6, OpenEye FRED) was selected to perform a virtual screening using a database of ca. 700 molecules. The six best-scoring compounds identified were tested in in vitro assays. A complete inhibition kinetic characterization carried out on the most promising molecule (n-Heptyl β-D-glucopyranoside, N7G) showed an inhibition constant of 7.8 ± 0.6 µM. This study represents an initial step towards the development of new EaAmsI inhibitors able to act as antibacterial agents against E. amylovora infections. [ABSTRACT FROM AUTHOR]

Isolates of the fire blight pathogen Erwinia amylovora with high-level resistance to Oxytetracycline (minimal inhibitory concentration [MIC] > 100 µg/ml) and to streptomycin (MIC > 100 µg/ml) were recovered from four commercial pear orchards in California between 2018 and 2020. The two representative Oxytetracycline- and streptomycin-resistant (OxyTcR-SmR) sttains 32-10 and 33-1 were as virulent as the antibiotic susceptible strain 13-1 in causing blossom blight of pear and were recovered more than 50% of the time 7 days after co-inoculation to pear flowers with strain 13-1. In the field, inoculation of strain 32-10 to pear flowers that were pretreated with Oxytetracycline at 200 µg/ml did not reduce disease compared with an untreated control. Four OxyTcR-SmR strains were subjected to draft genome sequencing to identify the genetic determinants of antibiotic resistance and their location. A 43.6-kb IncX plasmid, designated pX11-7, was detected in each of the four strains, and this plasmid encoded the tetracycline-resistance gene tetB and the streptomycin-resistance gene pair strAB within a large putatively mobile genetic element consisting of the transposon Tn10 that had inserted within the streptomycin-resistance transposon Tn60S2. We also determined that pX11-7 was conjugative and was transferred at a rate that was 104 to 105 higher into an E. amylovora strain isolated in California compared with an E. amylovora strain that was isolated in Michigan. The occurrence of high levels of resistance to both Oxytetracycline and streptomycin in E. amylovora strains from commercial pear orchards in California significantly limits the options for blossom blight management in these locations. [ABSTRACT FROM AUTHOR]

Nighttime applications of germicidal UV light (UV-C) have been used to suppress several fungal diseases of plants, but less is known of UV-C's potential to suppress bacterial plant pathogens. Fire blight of apple and pear, caused by the bacterium Erwinia amylovora, is difficult to suppress using cultural practices, antibiotics, and host resistance. We therefore investigated the potential of UV-C as an additional means to manage the disease. Laboratory assays confirmed that in vitro exposure of cultures E. amylovora to UV-C at doses ranging from 0 to 400 J/m² in the absence of visible light was more than 200% as effective as cultures exposed to visible light after the same UV-C treatments. In a 2-year orchard study, we demonstrated that with only two nighttime applications of UV-C at 200 J/m² made at bloom resulted in an incidence of blossom blight and shoot blight equivalent to the results viewed when antibiotic and biopesticide commercial standards were applied. In vitro dose-response studies indicated consistency in pathogen response to suppressive UV-C doses, including pathogen isolates that were resistant to streptomycin. Based on these results, UV-C may be useful in managing bacterial populations with antibiotic resistance. Concurrent measurements of host growth after UV-C applications indicated that the dose required to suppress E. amylovora had no significant (P > 0.05) effects on foliar growth, shoot extension, internode length, or fruit finish but substantially reduced epiphytic populations of E. amylovora on host tissues. [ABSTRACT FROM AUTHOR]

Fire blight, caused by Erwinia amylovora, is an economically important disease in apples and pears worldwide. This pathogen relies on the type III secretion system (T3SS) to cause disease. Compounds that inhibit the function of the T3SS (T3SS inhibitors) have emerged as alternative strategies for bacterial plant disease management, as they block bacterial virulence without affecting growth, unlike traditional antibiotics. In this study, we investigated the mode of action of a T3SS inhibitor named TS 108, a plant phenolic acid derivative, in E. amylovora. We showed that adding TS 108 to an in vitro culture of E. amylovora repressed the expression of several T3SS regulon genes, including the master regulator gene hrpL. Further studies demonsttated that TS 108 negatively regulates CsrB, a global regulatory small RNA, at the posttranscriptional level, resulting in a repression of hrpS, which encodes a key activator of hrpL. Additionally, TS 108 has no impact on the expression of T3SS in Dickeya dadantii or Pseudomonas aeruginosa, suggesting that its inhibition of the E. amylovora T3SS is likely species specific. To better evaluate the performance of T3SS inhibitors in fire blight management, we conducted five independent field experiments in four states (Michigan, New York, Oregon, and Connecticut) from 2015 to 2022 and observed reductions in blossom blight incidence as high as 96.7% compared with unseated trees. In summary, the T3SS inhibitors exhibited good efficacy against fire blight. [ABSTRACT FROM AUTHOR]

Fire blight, caused by the plant-pathogenic bacterium Erwinia amylovora, is a devastating disease that occurs on rosaceous plants, including pears and apples. E. amylovora is indigenous to North America and was spread to the Eurasian continent in the second half of the 20th century through contaminated plant materials. In 2016, fire blight was first observed in Yili, Xinjiang Province, in Northwestern China. Since then, it has spread to most pear-producing regions in Xinjiang Province and parts of Gansu Province. The disease has caused severe damage to China's pear and apple industries, including the 2017 disease epidemic in Korla, Xinjiang, which caused an overall yield reduction of 30 to about 50% in Korla and the destruction of over 1 million pear trees. Over the past few years, a combined effort of research, extension, and education by the Chinese government, scientists, and fruit growers has greatly alleviated outbreaks and epidemics in affected regions while successfully limiting the further spread of fire blight to new geographical regions. Here, we review the occurrence, spread, and damage of this disease to the Chinese fruit industry, as well as the management options used in China and their outcomes. We also discuss future perspectives for restraining the spread and alleviating the damage of fire blight in China. [ABSTRACT FROM AUTHOR]

After transitioning from periodic to model-based control policy for fire blight blossom infection, it is crucial to provide the timing of field application with easy and accurate information. To assess the risk of blossom infection, Maryblyt was employed in 31 sites across apple-producing regions nationwide, including areas prone to fire blight outbreaks, from 2021 to 2023. In 2021 and 2023, two and seven sites experienced Blossom Infection Risk-Infection warning occurrences among 31 sites, respectively. However, in 2022, most of the sites observed Blossom Infection Risk-Infection from April 25 to 28, highlighting the need for blossom infection control. For the comparison between the two model-based control approaches, we established treatment 1, which involved control measures according to the Blossom Infection Risk-Infection warning and treatment 2, aimed at maintaining the Epiphytic Infection Potential below 100. The analysis of control values between these treatments revealed that treatment 2 was more effective in reducing Blossom Infection Risk-Infection and the number of days with Epiphytic Infection Potential above 100, with respective averages of 95.6% and 93.0% over the three years. Since 2022, the implementation of the K-Maryblyt system and the deployment of Automated Weather Stations capable of measuring orchard weather conditions, with an average of 10 stations per major apple fire blight county nationwide, have taken place. These advancements will enable the provision of more accurate and timely information for farmers based on fire blight models in the future.

Recently, the domestic plant disease control policy for fire blight has been implemented partial control in ad-dition to burial control. In this study, an on-site management survey was conducted targeting orchards that implemented partial disease control from 2019 to 2020 in order to find efficient implementation methods for partial disease control. As a result of an investigation into 22 pear and apple orchards in Cheonan and Chungju, 7 orchards were buried. The upper part of the cut infected plants was burned at 16 orchards and covered with plastic vinyl after lime treatment at 6 orchards. The lower stumps of cut infected plants were burned at 7 orchards and covered with plastic vinyl after lime treatment at 15 orchards. There were two orchards where suckers appeared on the stumps even though covers were applied. There was no infection by Erwinia amylovora in the suckers. The conservation condition of lime treatment was good, but warning signs were absent at 6 orchards. Most orchards treated the stumps and surrounding areas with glyphosate-isopropylamine herbicide. The effect of partial control was judged to be safe.

Abstract Background Fire Blight, incited by Erwinia amylovora, is one of the most damaging pear and apple diseases in the world. Fire blight was introduced to Egypt in the 1960 and threatens the Egypt’s costs for pear industry. Currently, Phage therapy is considered to be secured biological method for controlling plant bacterial diseases. This investigation aimed to isolate and identify molecularly for bacteria causing fire bright disease. As well as isolation and identification bacteriophages via spot and plaque assay techniques from pear fire blight lesions and soil. On the other hand, bacteriophages were identified based on plaque morphology, virion morphology, physical characters, profile of DNA restriction and protein. Results Pathogenicity test revealed that healthy seedlings and pear fruits were responsive to fire blight E. amylovora. Considering the relatively wide host range and greatest protein and genetic variability, using restriction enzyme pattern, the three diversity phage isolates named, EAP1, EAP2 and EAP3 showed a lack of diversity out of five were fatherly characterized. The phages confirmed the close relation of EAP1, EAP2 to Siphoviridae (hexagonal head and long flexible non-contractile tail) and EAP3 to Myoviridae (icosahedral head and contractile tail). The phages retained higher lytic competence of 90.4; 92.68 and 95.25% for EAP1, EAP2 and EAP3, respectively. The phages were stable at strong alkaline (pH 10) 2% salt solution conditions and UV spectra. While EAP3 phage revealed the hexagonal head and very short tail that belongs to Myoviridae family. Bacteriophages were characterized by digestion of the phage DNA with three restriction endonucleases and were placed into three groups based on the patterns. Bacteriophages were 9 used for reducing bacterial infection populations and severity on pear. In a bioassay, the biocontrol of E. amylovora was evaluated using disks of immature pear fruit. On the pear disk surface, bacterial exudate was considerably suppressed by all phage isolates. According to measurements of the bacterial population still present on the disk surface, phage therapy could reduce it by up to 97%. Bacteriophages reduced pear fire blight disease severity on pear fruit trails. Conclusion The results indicated that bacteriophage isolates may demonstrate variable reactivity against E. amylovora. Bacteriophages reduced pear fire blight disease severity on pear fruit trials. The results indicated that bacteriophage isolates may demonstrate variable reactivity against E. amylovora.

The subject of the study was to identify the antagonism of the Lactobacillus plantarum strain 17 M against the causative agent of fire blight, the bacterium Erwinia amylovora, and to evaluate its protective capabilities on apple blossoms against this disease. For comparison 9 strains of lactic acid bacteria from the LLP "SPC of Microbiology and Virology" collection were included in the study. Strain 17 M appeared to be superior in limiting the growth of the pathogen on all 3 liquid media tested. Its maximum inhibitory activity was proved on MRS Broth medium. The analysis of the secondary metabolites produced by strain 17 M in liquid medium revealed that it consisted mainly of acetic acid (53.2 ± 4.3%), lactic acid (16.3 ± 2.3%) and 2,3-butanedione (14.84 ± 4.1%). The presence of other organic compounds was also detected but in a smaller amount. Study on influence of those compounds on growth of E. amylovora showed that lactic acid at concentration of 5% showed inhibitory activity but it was not toxic to apple flowers. The effectiveness of strain 17 M culture liquid diluted with sterile water and added to E. amylovora inoculum at 10% or 20% was 76.7 ± 5.8% and 88.3 ± 12.6%, respectively. This study confirms the potential use of strain 17 M as an active microbial agent to combat fire blight of fruit crops in Kazakhstan. [ABSTRACT FROM AUTHOR]

Clonal rootstocks of apple trees are one of the main components of intensive horticulture, and they play an important role in regulating tree growth, yield, fruit quality, and resistance to biotic and abiotic stresses. In the two-year monitoring survey reported here, eleven rootstocks mainly used for cultivar grafting in Kazakhstan were assessed for fire blight resistance, taking genetic background into consideration. The loci FB_F7 on LG7 and FB_MR5 and RLP1 on LG3 were analyzed on the basis of SCAR and SNP markers. The rootstocks 'Geneva 41', '62-396', and 'Geneva16', bearing resistant alleles for five markers (AH0JFXM, AH21B92, AH4AAGA, AH5I8MI, and AH6R6SQ), four markers (AH0JFXM, AH21B92, AH4AAGA, and AH5I8MI), and one (AH4AAGA) SNP marker, respectively, were not infected during the monitoring period despite weather conditions in 2022 being favorable for the development and spread of Erwinia amylovora. No connection was identified between the presence of a resistant allele for the AE10-375 marker and fire blight resistance responses. This is the first study to evaluate the fire blight resistance of foreign and local rootstocks grown in the Kazakhstan southern region. [ABSTRACT FROM AUTHOR]

The YopJ group of acetylating effectors from phytopathogens of the genera Pseudomonas and Ralstonia have been widely studied to understand how they modify and suppress their host defence targets. In contrast, studies on a related group of effectors, the Eop1 group, lag far behind. Members of the Eop1 group are widely present in the Erwinia-Pantoea clade of Gram-negative bacteria, which contains phytopathogens, non-pathogens and potential biocontrol agents, implying that they may play an important role in agroecological or pathological adaptations. The lack of research in this group of YopJ effectors has left a significant knowledge gap in their functioning and role. For the first time, we perform a comparative analysis combining AlphaFold modelling, in planta transient expressions and targeted mutational analyses of the Eop1 group effectors from the Erwinia-Pantoea clade, to help elucidate their likely activity and mechanism(s). This integrated study revealed several new findings, including putative binding sites for inositol hexakisphosphate and acetyl coenzyme A and newly postulated target-binding domains, and raises questions about whether these effectors function through a catalytic triad mechanism. The results imply that some Eop1s may use a catalytic dyad acetylation mechanism that we found could be promoted by the electronegative environment around the active site. [ABSTRACT FROM AUTHOR]

Wild apples and their hybrids are valued as a source of genetic resistance to biotic and abiotic stress. Malus niedzwetzkyana is an endangered ornamental apple species endemic to Southeast Kazakhstan, the center of Malus domestication. To test the fire blight resistance of M. niedzwetzkyana, eight plant genotypes were inoculated with a local strain of Erwinia amylovora. The genotypes possess different genetic backgrounds, which was confirmed via SSR profiling. Four out of eight displayed moderate to severe symptoms of fire blight infection, while the three wild genotypes proved resistant. To search for the source of the resistance, the samples were tested for the presence of FBF7 QTL using SCAR markers, where seven genotypes tested positive for one of the markers (AE10-375) and one for the other (GE80-19). No correlation between resistance phenotype and FBF7 QTL was confirmed, indicating the source lies elsewhere. Developing detailed genetic and phenotypic profiles of wild apple species helps advance both the preservation efforts and marker-assisted selection in apple breeding. [ABSTRACT FROM AUTHOR]