Search

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]

We evaluated the effectiveness of three different treatment groups at managing apple shoot blight, and the resulting canker incidence and canker length on wood caused by Erwinia amylovora. Preventative foliar sprays or trunk injections of giant knotweed extract (Regalia), oxytetracycline (Arbor-OTC or FireLine + Regulaid), or streptomycin (Agri-mycin/FireWall + Regulaid) were applied to mature 'Fuji' trees. Regalia and oxytetracycline were ineffective at reducing shoot blight severity, showing poor disease reductions of 18.2% and 24.3% compared to untreated controls across both years. Streptomycin was effective at controlling shoot blight severity when applied as a spray application, reducing necrosis by up to 93.9% across both years. Canker incidence was also poorly reduced by Regalia and oxytetracycline with an average decrease of 33.3% and 52.4%, respectively. Again, spray applications of streptomycin were most effective at reducing canker incidence (95.2%). When present, canker length was best controlled by spray applications of streptomycin, showing an average reduction of 95.7%. The effectiveness of Regalia and oxytetracycline was poor, reducing canker length by only 30.4% and 43.5%, respectively. Trunk injections of Regalia were consistently less effective than spray applications. Compared to their spray application counterpart, Regalia injections were, on average, 12.5%, 26.3%, and 25.1% less effective at reducing shoot blight severity, canker incidence, and canker length, respectively. Injected Arbor-OTC was more effective than spray applications of oxytetracycline. On average, Arbor-OTC injections were up to 28.3%, 40.1%, and 30% more effective at reducing shoot blight severity, canker incidence, and canker length compared to spray applications. Overall, Regalia and oxytetracycline were not as effective as streptomycin at controlling fire blight. The search for organic antibiotic alternatives for shoot blight and canker control continues, as cankers are increasing in economic importance by causing bearing wood and young tree death. [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]

Flowers serve as hubs for biotic interactions with pollinators and microbes, which can significantly impact plant reproduction and health. Previous studies have shown that the flower microbiota undergoes dynamic assembly processes during anthesis. However, the influence of foraging pollinators on the assembly and dispersal of the flower microbiota and the transmission of plant pathogens remains poorly understood. In this study, we used insect exclusion netting to investigate the role of pollinators in the assembly of the microbiota on apple stigma and the transmission of the fire blight pathogen Erwinia amylovora. We found that excluding pollinators had a minor impact on the community diversity and composition of the apple stigma microbiota, while the flower's developmental stage had a strong influence. Additionally, pollinator exclusion altered bacterial dispersal and the relative abundance of different bacterial species, including E. amylovora, suggesting that pollinators play a role in transmitting plant pathogens. Using a reporter system, we demonstrated that bumble bees can transmit the fire blight pathogen from an infected flower under controlled growth conditions. Our study highlights the importance of intrinsic and pollinator‐independent microbes as sources of inoculum for the stigma microbiota and underscores the role of foraging pollinators in vectoring plant pathogens. [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]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The U.S. Department of Agriculture (USDA) has performed European pear (Pyrus communis L.) scion breeding for over a century. The breeding program started in the early 1900s by Merton B. Waite in the Washington D.C. area and the program's main goal was to develop host resistance to the devastating disease fire blight, caused by Erwinia amylovora. Most of the historic European pear cultivars being produced in the U.S. were susceptible to fire blight, prompting a need to breed for resistance. More than six generations of USDA breeders have continued this effort to breed disease-resistant European pears. Along with fire blight resistance, the pear breeding programs sought improved fruit quality, cold hardiness, and resistance to psylla (Cacopsylla pyricola Foërster), a significant insect pest of pear. Herein, we discuss the history of the program through each generation of breeder(s). We also present breeding aims, parental selection, and releases. In total, the program has released ten named pear varieties between 1938 and 2022. [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]

The rapid emergence of multidrug-resistant (MDR) bacteria has motivated researchers to develop new antibiotic agents including antimicrobial adjuvants that resensitise against multidrug-resistance. In this study, four peptides, two 12-mer and two 8-mer derived from the primary structure of human glucose-dependent insulinotropic polypeptide (GIP), were synthesized by solid-phase peptide synthesis (SPPS). These peptides were designated as AO1, AO2, AO3, and AO4, respectively. Their antimicrobial activity was tested against bacteria possessing an AcrAB-TolC efflux pump system, namely Escherichia coli TG1 and Erwinia amylovora 1189. Although the peptides were shown to have no antimicrobial activity, through a synergistic action they each reduced the MIC values of the selected AcrAB-TolC antibiotic substrates by 4 to 8-fold in E. coli TG1 and 4 to 16-fold in E. amylovora 1189. The activity of synthetic peptides as AcrAB-TolC inhibitors in E. coli TG1 and E. amylovora 1189 was tested by intercellular ethidium bromide (EtBr) accumulation assay at different concentrations ranging from 12.5 to 100 µg mL− 1. When compared to a reference efflux pump inhibitor, the four peptides each demonstrated good inhibitory action, with the optimum being 100 µg mL− 1. Our results show these to be promising lead peptides for further development as potential antibacterial adjuvants against MDR bacteria. [ABSTRACT FROM AUTHOR]

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.

Erwinia amylovora is a gram-negative plant pathogen that causes fire blight in apple and pear trees, resulting in significant damage worldwide. In this study, we monitored the emergence of fire blight from 2019 to 2023 to determine the emergence patterns and the factors affecting the outbreak of the disease. As a result of the 5-year survey on the emergence of fire blight, a total of 2,029 cases have emerged, mostly in apple trees of 1,378 cases (67.9%) followed by 645 cases (31.8%) in pear trees, and from quince, hawthorn, and mountain ash trees. Fire blight appeared in specific areas of Gyeonggi, Chungnam, Gangwon, and Chungbuk provinces in 2019, but spread to Andong and Yesan in 2021, Muju and Bonghwa in 2023. In 2020 and 2021, there were 744 and 618 cases of fire blight outbreaks, respectively, compared to other years (188–245 cases/year). Notably, 914 of these cases were observed in apple trees from May to July, with 667 cases reported in Chungju and Jecheon. The incidence of fire blight was positively correlated with the daily maximum temperatures and rainy days in January and February, as well as the rainy days in May and June. The average age of the diseased pear trees was 25 years, higher than the 10-year average age of the apple trees. This study provides fundamental information to understand the status and factors affecting the fire blight emergence in Korea. Prevention measures should be established through continuous analysis of the status of fire blight.

Aims The Gram-negative bacterium Erwinia amylovora (Ea) is the causal agent of fire blight, a devastating disease of apples and pears. In the fire blight disease cycle, Ea grows in different plant tissues, each presenting a distinct nutrient environment. Here, we investigate the ability of aspartate and tyrosine double auxotroph Ea lines to proliferate on apple flower stigma surfaces representing the epiphytic growth stage of Ea and in developing fruitlets representing one endophytic growth stage of Ea. Methods and results Heterologous complementation studies in an Escherichia coli aspartate and tyrosine auxotroph verify that Ea aspartate aminotransferase (AspC) and tyrosine aminotransferase (TyrB) act as aspartate and tyrosine amino transferases. Growth analysis reveals that Ea aspC tyrB mutants multiply to near-wild-type levels on apple flower stigmas and immature fruitlets. Conclusions Ea AspC and TyrB are reciprocally complementing for aspartate and tyrosine synthesis in Ec and in Ea. Ea aspC and tyrB mutants obtain sufficient aspartate and tyrosine to support multiplication on stigma surfaces and virulence in immature fruitlets. [ABSTRACT FROM AUTHOR]

A greater genetic diversity is essential for disease resistance in particular, and intergeneric hybridization makes this possible. The genus Cydomalus (syn: Cydolus), which is frequently used as rootstock, was derived from intergeneric hybridization between Cydonia oblonga Mill. and Malus domestica Borkh in Moldova and Bulgaria. It is known that hybrids from this genus exhibit quince and/or apple characteristics and some of them have been identified with reddish fruit skin color in Türkiye in the last decade. Erwinia amylovora Burril. is the most devastating bacterial disease in the Rosaceae family, and there have been no reports of Cydomalus. In this study, fire blight susceptibility index of three Cydomalus genotypes, were collected from İzmir and Manisa provinces, and two important quince rootstocks were determined by artificial inoculations with the most virulent Erwinia amylovora strain of our collection, under greenhouse conditions for two consecutive years. In addition, susceptibility levels of two Cydomalus genotypes were observed under natural disease pressure habitats. In line with the results of artificial inoculations, two of Cydomalus genotypes were determined to be more tolerant to fire blight disease than quince rootstocks and these genotypes could be used in breeding studies. Moreover, Cydomalus genus was identified as the new host for Erwinia amylovora. [ABSTRACT FROM AUTHOR]

The current investigation was conducted to assess the antagonistic activity of Lacticaseibacillus paracasei M12, a novel strain, against the pathogenic agent Erwinia amylovora E22, which causes fire blight in fruit crops. The E. amylovora E22 strain was isolated from Golden Delicious floral colonization dynamics and specificity of Aureobasidium pullulans strains used to suppress fire blight in apple fruit. The L. paracasei M12 strain was collected from the phyllosphere of the garden cenosis in the Almaty region of Kazakhstan. Identification of both isolates relied on morphological and biochemical tests as well as PCR analysis. Results indicated that the zone of pathogen growth inhibition due to the action of the L. paracasei M12 strain was 41.5 ± 1.5 mm. The maximum inhibitory activity of this antagonist was observed on the 7th day of fermentation. Lactic acid constituted the largest percentage in the cultural broth component composition (43.55%) and exhibited inhibitory effects against E. amylovora E22. Evaluation of various concentrations of the broth in vitro demonstrated that the use of the original broth (100%) resulted in complete inhibition of pathogen growth. A parallel outcome was observed in tests conducted on immature pear fruits, where those treated with 100% of M12 culture broth exhibited complete protection against fire blight infection, while 50% and 20% concentrations showed a slight appearance of the disease. Furthermore, the incorporation of TWEEN® 80 as an adhesive agent enhanced the antagonistic activity of the L. paracasei M12 strain in vitro. Consequently, the L. paracasei strain M12 emerges as a promising candidate for the development of a novel biopesticide targeting fire blight. It was shown that the biological efficacy of L. paracasei M12 against fire blight during double treatment of Aport and Starkrimson fruit trees was 80.3% and 80.7%, respectively. [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]

The genetic diversity of 52 Erwinia amylovora isolates from pome fruit trees with fire blight in Central and Eastern Georgia from the years 2020–2022 was examined using specific PCR and genotyping of CRISPR repeat regions 1 and 2. The analysis identified three distinct genotypes: (A, a, α), matching historical Western European strains; (A, z, α), distinctive for Georgia and differing by a three-spacer deletion in CRR2 (2034–2036); as well as novel genotype (A, ä, α), which was not observed previously. Genotypes (A, a, α) and (A, z, α) were found to coexist geographically in all four regions investigated, whereas genotype (A, ä, α) was reported only in one case in the region of Kvemo Kartli. On separate instances, multiple genotypes were detected even within the same orchard or tree, illustrating the complex genetic landscape of E. amylovora in the country. [ABSTRACT FROM AUTHOR]

Fire blight caused by Erwinia amylovora reached Kazakhstan in 2008. Here, the disease poses a threat not only to agricultural production of apples and pears, but also to the forests of wild Malus sieversii, the progenitor of most domesticated apple varieties worldwide. In the period 2019–2021, the spread of fire blight in the growth area of wild apples was limited by the weather conditions. In 2022, late spring and early summer were characterized by increased rainfall and moderate temperatures favorable for the disease. The goal of this study was to monitor the distribution of fire blight in private households and small orchards in the zones adjacent to wild apple distribution areas. A total of 91 samples with fire blight-compatible symptoms were collected from cultural apples (68), wild apple (10), pear (5), hawthorn (7), and quince (1) in south-eastern and eastern Kazakhstan, resulting in 21 isolates (one from pear, one from quince, and 19 from apple) of E. amylovora. All isolates belonged to the archetypal CRISPR genotype A. Considering the relative proximity of the infections to the forests of wild M. sieversii, additional measures for fire blight control and prevention will have to be implemented, including state monitoring of the wild apple forests for disease symptoms and awareness campaigns for specially protected natural territories that safeguard M. sieversii, as well as for local pomaceous-fruit growing communities. [ABSTRACT FROM AUTHOR]

Fire blight disease, caused by Erwinia amylovora is present worldwide and affects over 40 countries in Europe where it is listed as a quarantine or regulated pest often due to ineffective control strategies maladapted to the respective production systems. In Portugal, the disease was confirmed in 2010 and the occurrence of disease outbreaks in new production areas has risen over the years. The disease affects the national production of apple and pear fruits, with greater impact on the national pear variety 'Rocha', widely exported to European countries and Brazil. The mild temperatures and high relative humidity promote the progression of the disease during winter, revealing the potential activity of the bacterium in the latency period (LP) of the host. Infection alert risk using the established predictive models Maryblight TM, Cougarblight and BIS98 was put in place in 2013 by Centro Operativo e Tecnológico Hortofrutícola Nacional (COTHN). These attempts to control the spread of this disease, showed low accuracy for the Portuguese epidemiological reality. Within the framework of project Fire4CAST we developed a new epidemiological model to predict fire blight disease using a systems biology approach integrating microbiological, cytological and genomic pathogen data with phenological host development and climatic variables. The presence of E. amylovora was monitored in orchards with fire blight history using standard laboratory tests. Simultaneously, the implementation of immune-flow cytometry (IFCM) highlighted the viability of E. amylovora populations prevailing during winter and early spring, long before bloom risk period. The integration of the whole data set allowed the development of the Fire4CAST predictive model, able to monitor the expected infection date (EID) and to define accurate outbreak alarms. Fire4CAST model enabled the detection of outbreak risk during winter based on rules that consider climatic data variables, which were validated by effective presence of live and active E. amylovora populations and real-time quantitative PCR (qPCR) data, accomplishing a precision rate of 83%. Field application of Fire4CAST can hopefully guide the implementation of successful control strategies, leading to more sustainable pome chain production areas. [ABSTRACT FROM AUTHOR]

The paper presents an attempt to explain the potential mechanisms related to the biocontrol capacity of the four strains representing bacterial species in which this activity was observed for the first time (Pseudomonas vancouverensis L16, Pseudomonas chlororaphis subsp. aureofaciens 3M, Enterobacter ludwigii 43M and Pseudomonas protegens 59M). The P. protegens 59M strain showed the highest effectiveness in protecting pear fruitlets against fire blight. The phenotypic analyses of tested mechanisms showed that all strains demonstrated the ability of motility, hydrogen cyanide production and degradation of nicotinic acid. Also, all strains except E. ludwigii 43M, produced siderophores and P. vancouverensis L16 was able to produce biosurfactant, salicylic acid and indole-3-acetic acid (IAA) while the E. ludwigii 43M and P. chlororaphis subsp. aureofaciens 3M strains produced IAA and homoserine lactones (AHL), respectively. A study on the detection of genes encoding antibiotics characteristic of pseudomonads showed the presence of prnD in the P. chlororaphis subsp. aureofaciens 3M strain and phlD, pltC, pltB and pltC in P. protegens 59M, which suggested that the latter strain had the largest number of antibiotic-coding genes among all the strains tested. The regulatory gene gacA was also present in P. protegens 59M and P. chlororaphis subsp. aureofaciens 3M strains. However, none of the genes sought were detected in the L16 strain. It was assumed that the ability of strain P. protegens 59M to completely protect slices of pear fruitlet against E. amylovora infection is related to the production of antibiotics and possibly also to the other detected mechanisms of antagonism, such as siderophore, IAA and HCN production. [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]

Fire blight, caused by the bacterial pathogen Erwinia amylovora, continues to be a devastating disease affecting commercial apple and pear plantings in almost all areas of the world, with recent incursions into Korea and China. During the past two decades, significant gains in knowledge of E. amylovora and fire blight disease have been achieved, in topic areas such as genetic and genomic diversity, host-pathogen interactions, host resistance, and disease management. As we look forward to the next two decades and beyond of fire blight research, we summarize the current research knowledge in topics focused on E. amylovora pathogen and population biology and propose research questions that we hope can guide the field forward to gain the necessary understanding that will lead to sustainable management of this disease. [ABSTRACT FROM AUTHOR]

The persistence and progression of Erwinia amylovora in naturally infected orchards is still not fully understood and the majority of studies have been carried out under controlled or artificial infections. A major hurdle stems from the inability to characterize the viability of the bacterium in its natural state. Most standard tests, including real-time qPCR, fail to differentiate live from dead cells, while culture dependent methods lack sensitivity. Even in orchards with recurring infections, the detection of E. amylovora is erratic. Immuno-flow cytometry (IFCM) is considered a high throughput tool in clinics and food industry but has been rarely used as diagnostic test for plant pathogens. Two pear orchards with fire blight history, located in the central part of Portugal, were selected for epidemiological monitoring between February and June, from 2019 to 2022. A total of 440 samples were tested using EPPO standard diagnostic protocols. To address the epidemiological behaviour of E. amylovora, we devised an IFCM test using specific monoclonal antibodies and viability dyes, validated in a subset of 149 samples, testing positive in routine diagnostic tests. Our IFCM test was able to differentiate live and dead E. amylovora in naturally infected samples with concentrations as low as 3.54 × 104 cell·mL−1, confirming positive results for 91% these samples, while 19.4% were considered positive by isolation, 38% using conventional PCR and 95% for real-time qPCR. Temporal analysis showed the highest number of positive samples regardless of the method employed in April, May and June, while viability values measured with IFCM were the highest in April, coinciding with the exit of dormancy and early flowering of pear trees. Integrative analysis of E. amylovora viability and population dynamics over the growing season allowed identification of distinct outbreak risks associated with these Portuguese pear orchards. [ABSTRACT FROM AUTHOR]

Fire blight caused by bacterium Erwinia amylovora is one of the most damaging diseases of apple and pear trees and many other plant species of the Rosaceae family. So far, it has been detected in almost all areas of pome fruit cultivation and in some regions it causes economic damage every year. Plant protection against fire blight is aimed at both preventing their infection and controlling the disease. However, the protection of plants against bacteriosis is generally difficult due to the small range of plant protection products and the growing doubts about their safety for the environment. Limitations related to their use have resulted in an increased interest in alternative methods, including the method of biological protection using various microorganisms. The first research on biological control agents was conducted in the USA about 100 years ago. Currently, it is also carried out in other countries, especially where fire blight causes economic losses. Commercial products whose active ingredients are mainly bacteria have already been developed. This work is a review of the studies and achievements in this field from its beginnings focusing on the Gram-negative bacteria and bacteriophages as a biocontrol agents. [ABSTRACT FROM AUTHOR]

Fire blight is the most important bacterial disease in apple (Malus × domestica). Owing to the severity of the caused damages, fire blight resistance is an important breeding objective. In the past, various phenotypic screening methods and strategies have been used to identify new sources of fire blight resistance for breeding. In this study, breeding material, modern cultivars and heirloom accessions were phenotyped by artificial inoculation of shoots under greenhouse (n = 273) and flowers under field conditions (n = 20) and genotyped for known resistance genes and quantitative trait loci by using molecular markers. A comparison between the two phenotyping methods was made in relation to the two control varieties 'Gala Galaxy' and 'Enterprise'. The results obtained for the resistance sources FB_MR5, Fb_E and FB_F7 are consistent with previously published data, showing a large effect of the two major resistance genes FB_MR5 ('Malus × robusta 5') and Fb_E ('Evereste'). Genotypes carrying FB_F7 showed greater variation in their resistance levels, but were on average less susceptible than 'Gala Galaxy' and genotypes with no known resistance gene or quantitative trait locus (QTLs) in both tests. No correlation was found between the results of 18 genotypes phenotyped with both inoculation methods. The ranking of genotypes according to their flower and shoot fire blight resistance varied between the two methods. However, 11 of the 18 tested genotypes showed no significant difference between the results of the two methods. Additionally, it was found that flower shedding appears to be an important triggered mechanism for flower resistance to fire blight. [ABSTRACT FROM AUTHOR]

The genus Erwinia includes plant-pathogenic, non-pathogenic and even opportunistic human pathogens. Among them, Erwinia amylovora is one of the most studied species, as the etiological agent of the relevant necrotic plant disease fire blight. Its most important pathogenicity factor is amylovoran, an exopolysaccharide essential in the formation of a protective biofilm used by the bacterium to escape the plant protection mechanisms. Amylovoran biosynthesis, regulation and secretion require the concerted action of twelve genes clustered in a region spanning 16 kb, the ams operon. Most of the encoded proteins build and polymerize the repeating oligosaccharide units of galactose, glucose, glucuronic acid and pyruvate, others have signalling, regulation and secretion functions. We compared the ams operon organisation, predicted 3D structure of the encoded proteins of Erwinia amylovora in eighteen Erwinia species. We detected the presence of a paralog (for the amsG gene) and some rearrangements in the EPS biosynthetic operon in specific taxa that could be connected to the species-specific pathogenicity profile. The present study adds fundamental information about the genomic determinants of exopolysaccharide secretion in the Erwinia genus, and clarifies the evolutionary relationships among the genes in the ams operon. [ABSTRACT FROM AUTHOR]

Lectins, a large group of proteins present in all kingdoms of life can bind reversibly to glycans. The roles of plant lectins are diverse and include resistance to biotic or abiotic stress, notably bacterial resistance. A gene family encoding amaranthin-like lectins termed MdAGGs in apple (Malus domestica) has been identified to be overexpressed upon treatment with the plant resistance inducer acibenzolar-S-methyl (ASM) which promotes enhanced resistance to the fire blight disease caused by Erwinia amylovora (Ea). In this study, we first screened the ability of purified MdAGG10 to agglutinate bacterial cells in vitro among a range of bacterial species. Several bacterial species, either Gram positive or negative, either plant- or human-pathogens were found to be agglutinated by MdAGG10 in acidic conditions. Apple and Arabidopsis lines constitutively overexpressing MdAGG10 were generated and evaluated for their resistance to, respectively, Ea and Ralstonia solanacearum, both plant pathogens that were found in our screening. Despite MdAGG10 protein accumulated in tissues of both apple and Arabidopsis lines, they remained susceptible to their respective pathogens. Interestingly, in vitro agglutination of Ea by MdAGG10 did not impair bacterial growth, suggesting that other plant molecules are involved in the resistance to fire blight triggered after an ASM treatment. [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]

Malus ×robusta 5, which has been the subject of extensive fire blight resistance research over time, is highly resistant or susceptible to the fire blight-causative bacterial pathogen, Erwinia amylovora – depending on the strain. M. ×robusta 5 has been crossed with susceptible apple cultivars and rootstocks, and inoculated with several E. amylovora strains in order to study the genetics and mechanism of its fire blight resistance and susceptibility. A strong resistance QTL was first mapped on linkage group 3 (LG3) of M. ×robusta 5 using an F1 progeny derived from a cross with the apple cultivar 'Idared' in Germany. This QTL was confirmed in two other F1 populations derived from crossing M. ×robusta 5 with the rootstock 'Malling 9' in New Zealand, and with 'Ottawa 3' in the USA. A second QTL on LG7 was detected in the 'Idared' × M. ×robusta 5 population but only with strains that break the LG3 QTL. However, in the US population of 'Ottawa 3' × M. ×robusta 5, the LG7 QTL was detected regardless of strain-specificity, unlike in the New Zealand population of 'Malling 9' × M. ×robusta 5 where the LG7 QTL was not also detected. Here, we report the detection of the LG7 QTL in a different 'Malling 9' × M. ×robusta 5 population in Germany, and confirm the independence of the LG7 locus to E. amylovora strains. [ABSTRACT FROM AUTHOR]

Fire blight, caused by the bacterial pathogen Erwinia amylovora, is a severe bacterial disease of apple and pear that can quickly destroy whole plants. In the last decade, it was also detected in Central Asia, where wild pomaceous fruit plants represent the dominant species in mid-altitude forests and constitute a critical foundation for the entire ecosystem. Efficiently informing farmers, forestry services and private persons about the instances and dangers of fire blight, the correct way to recognize the symptoms, and the methods of disease control is thus of paramount importance in a vast and fragmented natural landscape like the one characterizing countries like Kyrgyzstan, Kazakhstan and Tajikistan. For that purpose, we have developed an app for smartphones and mobile devices that can inform stakeholders about fire blight, simultaneously allowing a citizen science approach for mapping the spread of the disease in Central Asia. The app is available in the three national languages as well as in Russian, English, and German, and can easily be adapted to new countries, languages or even diseases. [ABSTRACT FROM AUTHOR]

Fire blight represents a great threat to apple and pear production worldwide. The ability of its causal agent, Erwinia amylovora, to spread rapidly in the host plants makes this devastating disease difficult to manage. Copper and antibiotics are still the most effective solutions to control fire blight, although their application contribute to environmental pollution and to the development of E. amylovora resistant populations. Thus, there is an urgent need to find new alternatives to such plant protection products. In this review, we summarized what is known on E. amylovora biology, as the knowledge of the plant pathogen biology is essential to develop eco-friendly management strategies. Notably, the presence of E. amylovora alone does not necessarily result in the disease development as it is the final outcome of multiple interactions established between E. amylovora cells, flower microbiota, plant host, insect vectors and environment. For instance, specific humidity and temperature create the suitable conditions for E. amylovora to grow and reach the specific cell density needed for plant infection. Once fire blight develops, insects act as potential vectors of E. amylovora, playing a role in the dispersal of the disease. The host plant represents an important factor as its susceptibility varies among the species belonging to the Rosaceae family. Recent studies showed apple flower microbiota might promote or hinder the infection progress, thus representing a possible source of new biocontrol agents effective in controlling E. amylovora. [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]

A strong fire blight resistance QTL (Mfu10) was previously detected on linkage group 10 (LG10) of Malus fusca accession MAL0045, using several strains of the causative bacterium, Erwinia amylovora. As no strain capable of breaking the resistance of MAL0045 has been found, we hypothesized that another locus contributes to its fire blight resistance. However, none was detected with strains previously tested on the progeny. Here, an avrRpt2EA mutant strain (Ea1038) with the chromosomal S-allele deleted and complemented with the less aggressive C-allele, was used to phenotype MAL0045 × 'Idared' progeny. We performed phenotype-genotype analyses using the first genetic map of MAL0045, which is scarcely dense, and a recently constructed saturated map. As expected, Mfu10 was detected on LG10 with Ea1038, as was previously with other strains. Interestingly, a QTL with a logarithm of odds (LOD) thresholds of 5.5 and 2.9, significant at the genome-wide and chromosome levels, respectively, was detected with Ea1038 on LG16 (Mfu16) in a subset of 76 individuals, but only using the saturated map. Progenies carrying both Mfu10 and Mfu16 were significantly more resistant than progenies carrying only Mfu10. However, the LOD of Mfu16 diminished to 2.6 in a larger subset of individuals. We hypothesize that Mfu16 is present in the genome of MAL0045 albeit unstable in the progeny. [ABSTRACT FROM AUTHOR]

Erwinia amylovora, the primary cause of fire blight, is thought to be one of the most difficult crop diseases to eradicate. The study aimed to evaluate the performance of essential sesame oil (SO) and silver nanoparticle synthesized by sesame oil SO-AgNPs against E. amylovora. Using GC-MS, it was found that essential sesame oil contains the main component of the oil was sesamin, asarninin, heptane, c-Sitosterol, anethol, and trimethyl -6- ((s) - 4-methylcyclohexan – 3 – en-1-yl)) tetrahydro -2H-pyran. The diluted sesame oil (SO) was used as a reducing agent in synthesis of AgNPs in aqueous solution. By using UV-Visible spectrophotometry (UV–Vis), Dynamic Light Scattering (DLS), High Resolution Transmission Electron Microscopy (HRTEM), and Fourier Transformer InfraRed (FTIR) analysis, the produced Ag NPs were studied. The average particle size of the spherical Ag NPs was determined to be 54.98 nm using data from HRTEM and DLS. SO-Ag NPs (20 µg/ml) showed a promising antibacterial against E. amylovora, producing a 22.9 mm Zone of Inhibition (ZOI) against E. amylovora, followed by SO-Ag NPs (10 ug/ml) that gave 18.2 mm ZOI., compared to gentamicin that produced 13.2 mm ZOI. The most effective inducers were SO-Ag NPs at 10 ug/ml, which decreased the percentage of disease severity by 27.5 and increased the percentage of protection against disease infection by 68.39%. SO-Ag NPs was the most effective inducers which decreased the contents of Malonaldehyde (MDA) and H2O2 by 41.3% and 77.1%. Applying SO-Ag NPs or SO lowered the level of malondialdehyde (MDA) and hydrogen peroxide (H2O2) and improved the fruit set and yield in infected trees. We could assume that, to prevent E. amylovora fire blight disease in pears, SO-Ag NPs, SO are safe, effective, and environmentally friendly alternatives to conventional antibiotics.  [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central European Agriculture is the property of Journal of Central European Agriculture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'high risk plants, plant products and other objects'. Taking into account the available scientific information, including the technical information provided by the applicant country, this Scientific Opinion covers the plant health risks posed by the following commodities: Sorbus aucuparia bare‐root plants and rooted plants in pots up to 7 years old and specimen trees in pots up to 15 years old imported into the EU from the UK. A list of pests potentially associated with the commodities was compiled. The relevance of any pest was assessed based on evidence following defined criteria. Three EU quarantine pests (Entoleuca mammata and Phytophthora ramorum (non‐EU isolates), Erwinia amylovora), were selected for further evaluation. For two of the selected pests (E. mammata and P. ramorum), the risk mitigation measures implemented in the UK and specified in the technical dossier were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The degree of pest freedom varies between the pests evaluated, with P. ramorum being the pest most frequently expected on the imported S. aucuparia plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9812 and 10,000 bare‐root S. aucuparia plants per 10,000 will be free from P. ramorum. [ABSTRACT FROM AUTHOR]

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]

Bacteria, fungi, and mammals contain lactonases that can degrade the Gram-negative bacterial quorum sensing (QS) molecules N-acyl homoserine lactones (AHLs). AHLs are critical for bacteria to coordinate gene expression and pathogenicity with population density. However, AHL-degrading lactonases present variable substrate ranges, including degradation of the Pencillium expansum lactone mycotoxin patulin. We selected Erwinia spp. as our model bacteria to further investigate this interaction. We find both native apple microbiome Erwinia spp. and the fruit tree pathogen Erwinia amylovora to be inhibited by patulin. At patulin concentrations that inhibited E. amylovora growth, expression of E. amylovora lactonase encoded by EaaiiA was increased. EaAiiA demonstrated the ability to degrade patulin in vitro, as well, as in vivo where it reduced apple disease and patulin production by P. expansum. Fungal-bacterial co-cultures revealed that the E. amylovora Δeaaiia strain failed to protect apples from P. expansum infections, which contained significant amounts of patulin. Our results suggest that bacterial lactonase production can modulate the pathogenicity of P. expansum in response to the secretion of toxic patulin. [ABSTRACT FROM AUTHOR]

The monitoring of plant diseases in nurseries, breeding farms and orchards is essential for maintaining plant health. Fire blight (Erwinia amylovora) is still one of the most dangerous diseases in fruit production, as it can spread epidemically and cause enormous economic damage. All measures are therefore aimed at preventing the spread of the pathogen in the orchard and containing an infection at an early stage [1–6]. Efficiency in plant disease control benefits from the development of a digital monitoring system if the spatial and temporal resolution of disease monitoring in orchards can be increased [7]. In this context, a digital disease monitoring system for fire blight based on RGB images was developed for orchards.Between 2021 and 2024, data was collected on nine dates under different weather conditions and with different cameras. The data source locations in Germany were the experimental orchard of the Julius Kühn Institute (JKI), Institute of Plant Protection in Fruit Crops and Viticulture in Dossenheim, the experimental greenhouse of the Julius Kühn Institute for Resistance Research and Stress Tolerance in Quedlinburg and the experimental orchard of the JKI for Breeding Research on Fruit Crops located in Dresden–Pillnitz. The RGB images were taken on different apple genotypes after artificial inoculation with Erwinia amylovora, including cultivars, wild species and progeny from breeding.The presented ERWIAM dataset contains manually labelled RGB images with a size of 1280 × 1280 pixels of fire blight infected shoots, flowers and leaves in different stages of development as well as background images without symptoms. In addition, symptoms of other plant diseases were acquired and integrated into the ERWIAM dataset as a separate class. Each fire blight symptom was annotated with the Computer Vision Annotation Tool (CVAT [8]) using 2-point annotations (bounding boxes) and presented in YOLO 1.1 format (.txt files). The dataset contains a total of 1611 annotated images and 87 background images. This dataset can be used as a resource for researchers and developers working on digital systems for plant disease monitoring.

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]

Actinomycetes have long been recognized as an important source of antibacterial natural products. In recent years, actinomycetes in extreme environments have become one of the main research directions. Streptomyces sp. KN37 was isolated from the cold region of Kanas in Xinjiang. It demonstrated potent antimicrobial activity, but the primary active compounds remained unclear. Therefore, we aimed to combine genomics with traditional isolation methods to obtain bioactive compounds from the strain KN37. Whole-genome sequencing and KEGG enrichment analysis indicated that KN37 possesses the potential for synthesizing secondary metabolites, and 41 biosynthetic gene clusters were predicted, some of which showed high similarity to known gene clusters responsible for the biosynthesis of antimicrobial antibiotics. The traditional isolation methods and activity-guided fractionation were employed to isolate and purify seven compounds with strong bioactivity from the fermentation broth of the strain KN37. These compounds were identified as 4-(Diethylamino)salicylaldehyde (1), 4-Nitrosodiphenylamine (2), N-(2,4-Dimethylphenyl)formamide (3), 4-Nitrocatechol (4), Methylsuccinic acid (5), Phenyllactic acid (6) and 5,6-Dimethylbenzimidazole (7). Moreover, 4-(Diethylamino)salicylaldehyde exhibited the most potent inhibitory effect against Rhizoctonia solani, with an EC50 value of 14.487 mg/L, while 4-Nitrosodiphenylamine showed great antibacterial activity against Erwinia amylovora, with an EC50 value of 5.715 mg/L. This study successfully isolated several highly active antimicrobial compounds from the metabolites of the strain KN37, which could contribute as scaffolds for subsequent chemical synthesis. On the other hand, the newly predicted antibiotic-like substances have not yet been isolated, but they still hold significant research value. They are instructive in the study of active natural product biosynthetic pathways, activation of silent gene clusters, and engineering bacteria construction. [ABSTRACT FROM AUTHOR]

Fire blight, a disease of pome fruits caused by the bacterium Erwinia amylovora, has become increasingly difficult to manage after the emergence of streptomycin-resistant strains. Alternative antibiotics and copper are available; however, these chemicals have use restrictions in some countries and also can carry risks of phytotoxicity. Therefore, there is growing interest in biological-based management options, with bacteriophage (phages) showing promise, as these naturally occurring pathogens of bacteria are easy to isolate and grow. However, there are several technical challenges regarding the implementation of phage biocontrol in the field, as the viral molecules suffer from ultraviolet radiation (UVR) degradation and can die off rapidly in the absence of the host bacterium. In this work, we assessed the efficacy of Erwinia phages and a commercial phage product for blossom blight control in the field across multiple locations in the eastern United States. In these tests, disease control ranged from 0.0 to 82.7%, and addition of a UVR protectant only resulted in significantly increased disease control in 2 of 12 tests. We also analyzed microbial community population changes in response to phage application. Changes in bacterial community diversity metrics over time were not detected; however, relative abundances of target taxa were temporarily reduced after phage applications, indicating that these phage applications did not have deleterious effects on the flower microbiome. We have demonstrated that biological control of fire blight with phages is achievable, but a better understanding of phage-pathogen dynamics is required to optimize disease control efficacy. [ABSTRACT FROM AUTHOR]

Fire blight, a devastating disease caused by Erwinia amylovora, poses a significant threat to pear and apple trees in Xinjiang province, China. In an effort to combat this pathogen, we isolated 10 bacteria from various components of apple and crabapple trees and conducted screenings to assess their ability to inhibit E. amylovora in vitro. Through biochemical tests and partial 16S rRNA gene sequencing, we identified two promising strains, Priestia megaterium strain H1 and Bacillus subtilis strain I2. These strains were then evaluated for their efficacy in biocontrol under controlled laboratory conditions, focusing on immature fruits and leaves. Remarkably, all selected antagonists exhibited the capability to reduce the severity of the disease on both fruit and leaves. P. megaterium strain H1 and B. subtilis strain I2 exhibited significant reductions in disease incidence on both immature fruits and leaves compared to the control. Specifically, on immature fruits, they achieved reductions of 53.39% and 44.76%, respectively, while on leaves, they demonstrated reductions of 59.55% and 55.53%, respectively. Furthermore, during the study, we detected the presence of lipopeptides, including surfactin, iturins, bacillomycin D, and fengycins, in the methanol extract obtained from these two antagonistic bacteria using thin-layer chromatography (TLC). Based on the results obtained, B. subtilis strain I2 and P. megaterium strain H1 exhibit considerable potential for controlling fire blight. However, further evaluation of their efficacy under natural field conditions is essential to validate their practicality as a biocontrol method. [ABSTRACT FROM AUTHOR]

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]