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Simple Summary: Clostridial infections in cattle are a major veterinary concern in Brazil, significantly impacting the country's livestock industry. These infections are caused by various Clostridium species, which are anaerobic, spore-forming bacteria capable of producing powerful toxins. The main clostridial diseases affecting cattle in Brazil include botulism, tetanus, blackleg, malignant edema and enterotoxemia. Prevention and control measures of regular vaccination programs are crucial in preventing clostridial diseases. Ensuring proper hygiene, especially during surgical procedures, and minimizing injuries can help reduce the risk of infection. Surveillance and research are essential for understanding the epidemiology of these diseases and improving control strategies. Monitoring outbreaks and investigating new cases help in adapting vaccination protocols and management practices. The economic impact of clostridial infections causes significant economic losses in Brazil's cattle industry due to high mortality rates, decreased productivity, and the costs associated with vaccination and treatment. Effective prevention and control strategies are crucial to mitigate these losses and ensure the health and productivity of cattle herds. Clostridial infections in cattle are a significant concern for Brazilian livestock. These diseases are caused by various species of Clostridium, which are known for their ability to produce potent toxins. Botulism in cattle is a serious and often fatal condition caused by the ingestion of neurotoxins produced by C. botulinum. This bacterium thrives in decomposing organic matter, such as spoiled feed, carcasses, and contaminated water. Tetanus is less common, but it is a serious disease that follows the contamination of wounds with Clostridium tetani spores. It results in muscle stiffness, spasms, and often death due to respiratory failure. Blackleg (C. chauvoei) is a disease that primarily affects young cattle, leading to acute lameness, swelling, and high fever. Malignant edema (C. septicum and others) is characterized by rapid onset of swelling at wound sites, and it can occur after injuries or surgical procedures. Enterotoxemia is triggered by the rapid growth of C. perfringens in the gut following excessive carbohydrate intake. This leads to toxin production that causes sudden death. In conclusion, clostridial bovine infections remain a persistent challenge for Brazilian cattle farmers. With continued focus on vaccination, good management practices, and research, the impact of these diseases can be minimized, safeguarding the livestock industry's economic viability. [ABSTRACT FROM AUTHOR]

In order to understand the epidemiological features of rapeseed blackleg in northern China, a 2‐year survey of blackleg on wild mustard (Sinapis arvensis) and rapeseed (Brassica napus) was done in Zhaosu County of Xinjiang Uyghur Autonomous Region of China. Blackleg frequently occurs on both plants in this region, with mean values of disease incidence reaching up to 28% on wild mustard and 14% on rapeseed. A total of 556 pycnidia‐forming fungal isolates were obtained from wild mustard (69) and rapeseed (487). Morphological and molecular identification indicated that all of the 69 isolates from wild mustard and the majority of the isolates from rapeseed (477/487, 97.9%) belonged to Leptosphaeria biglobosa 'canadensis' (Lb‐c); the remaining 10 isolates from rapeseed (10/487, 2.1%) belonged to L. biglobosa 'brassicae' (Lb‐b). Among 239 isolates of Lb‐c (62 from wild mustard and 177 from rapeseed), two mating‐type idiomorphs (MAT1‐1 and MAT1‐2) were detected. Chi‐square test showed that the ratio of MAT1‐1 to MAT1‐2 of isolates was 1:1, implying that the individuals of Lb‐c can frequently conduct sexual reproduction to produce ascospores as the primary airborne infection source. The virulence of 10 Lb‐c isolates from wild mustard and rapeseed and five Lb‐b isolates from rapeseed was determined on both plants. The results showed that the Lb‐c isolates from wild mustard were as virulent as isolates of Lb‐c and Lb‐b from rapeseed. Thus, Lb‐c can act as inoculum of rapeseed blackleg, and eliminating plants of wild mustard may improve efficacy of crop rotation in suppression of rapeseed blackleg. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) plays multiple and pivotal roles in plant defence against abiotic and biotic stresses. Blackleg, mainly caused by the fungal pathogen Leptosphaeria maculans, is one of the most devastating diseases in canola (Brassica napus) resulting in significant yield loss worldwide. Few studies have investigated the function of ABA biosynthesis genes in response to fungal pathogens. In this study, we identified and characterized BnNCED3 (9‐cis‐epoxycarotenoid dioxygenease) and BnTX1 (trithorax‐like factor) from B. napus. Transgenic B. napus 'Westar' plants overexpressing BnNCED3 showed enhanced adult plant resistance to blackleg infection. Chromatin immunoprecipitation‐quantitative PCR demonstrated that BnTX1 bound to the promoter region of the BnNCED3 gene. However, the overexpression of BnTX1 in transgenic plants decreased adult plant resistance to blackleg pathogen infection. The expression analysis confirmed the abundance of BnNCED3 transcripts was higher in BnTX1‐RNAi knockdown plants than in overexpressing plants. Thus, BnTX1 might play a negative role in regulating BnNCED3 gene expression and hence ABA biosynthesis, thereby affecting plant disease resistance. Our study provides a new model demonstrating how increased ABA levels can enhance plant disease resistance, which may lead to the characterization of minor/quantitative genes in the B. napus–L. maculans interaction. [ABSTRACT FROM AUTHOR]

Phytopathogenic bacteria of the genus Pectobacterium are responsible for several diseases that affect potato (Solanum tuberosum L.) production worldwide, including blackleg and tuber soft rot. These bacteria are highly diverse, with over 17 different species currently identified. However, some of the recently described species, such as Pectobacterium punjabense, are still poorly understood. In this study, we focused on P. punjabense isolates collected from diseased potato tubers in Russia in 2021. Whole-genome sequencing was used to characterise the genomic diversity of the pathogen and determine the biochemical profiles of the isolated bacteria. The ability of these isolates to cause soft rot symptoms was tested. A comparative assessment of the potential pathogenicity of the Pectobacterium isolates was conducted by infecting potato tubers and measuring the accumulation of biomass in a liquid medium during cultivation at different temperatures. A TaqMan qPCR assay was developed for the highly sensitive and specific characterisation of P. punjabense strains, which can be used in diagnostic systems. This is the first report on P. punjabense causing potato disease in the Russian Federation. [ABSTRACT FROM AUTHOR]

AbstractIn earlier studies, it was found that Leptosphaeria maculans could readily infect canola via fresh wounds but would require extended leaf wetness to infect intact tissues. We hypothesized that flea beetle feeding wounds might facilitate L. maculans infection under field conditions. Multi-year plot trials were conducted in western Canada to assess the effect of reducing flea beetle feeding wounds on canola seedlings with in-crop insecticide on subsequent blackleg infection. The experiment encompassed susceptible and resistant cultivars seeded into canola stubble from the previous year, with pyrethroid insecticide applied weekly commencing at trace feeding (<5%) to mitigate the insect damage. Fluopyram seed treatment was used as an additional treatment against early blackleg infection. Results from eight station years showed moderate feeding damage by flea beetles and generally high blackleg pressure, with the average disease incidence > 80%. Despite reduced feeding damage due to in-crop insecticide treatment, significant blackleg reduction was not observed. A greenhouse study revealed no correlation between puncture wounds on cotyledons and successful stem infection under high-inoculum conditions, suggesting that reduced insect feeding might not effectively counteract the heavy inoculum pressure resulting from canola residue in field trials. Fluopyram seed treatment did not reduce blackleg substantially, while resistant cultivars consistently exhibited effectiveness. Furthermore, harvested seed from plots with lighter blackleg often displayed lower levels of L. maculans inoculum contamination. [ABSTRACT FROM AUTHOR]

Pectinolytic bacteria were isolated from potato plants and tubers showing blackleg and soft rot symptoms, collected from fields and storages in the province of Ain Defla, Algeria, in the period from 2016 to 2018. Twelve Gram-negative pectinolytic bacterial isolates were obtained from the crystal violet pectate medium growth. These strains induced a hypersensitive reaction and soft rot symptoms when inoculated in tobacco leaves and potato tuber slices, respectively. Biochemical characterisation has revealed that the isolates correspond to two distinct phenotypes. Molecular identification by PCR using specific Dickeya spp. ADE1/ADE2 primers proved that four isolates S441, B74, D14 and A13 were of the genus Dickeya. Subsequently, additional biochemical tests have allowed their classification to the Dickeya biovar 3, known as the Dickeya solani species. Pathogenicity tests performed on potato, tomato and eggplant plants confirmed their virulence in various Solanaceae. Finally, the effects of initial inoculum concentration and of various temperature and humidity regimes were investigated. Maceration assays performed on potato tuber discs revealed more severe damage at high concentrations and when increasing temperature and humidity. This first study of D. solani causing blackleg and soft rot on potato in Algeria highlights the potential risks associated with this disease in the next years. [ABSTRACT FROM AUTHOR]

Brassica species, globally cultivated as economically important vegetable and oilseed crops, face challenges from pathogens impacting their growth and productivity. Among these, blackleg, caused by the fungal pathogen Leptosphaeria maculans, stands out as a significant concern. Genetic resistance, primarily mediated by resistance gene analogues (RGAs), is key to sustainable blackleg control. Utilising wild relatives of Brassica species presents a promising avenue for enhancing resistance to blackleg in cultivated crops. In this study, we employed the newly published Hirschfeldia incana reference genome to identify the genome-wide RGAs in H. incana. A total of 914 candidate RGAs were identified; the receptor-like protein kinases (RLK) family contained the highest number with 608 (66.53%), followed by the Transmembrane coiled-coil (TM-CC) family with 167 (18.27%), nucleotide-binding site-leucine-rich repeats (NLR) family with 98 (10.72%) and receptor-like proteins (RLPs) with 41 (4.48%). We conducted duplication analysis on the 914 candidate RGAs, which revealed gene duplication occurs frequently to expand the RGAs in H. incana and significantly contributes to plant defence responsiveness. The phylogenetic analysis provided insights into the diversification and functional implications of the identified groups. We used the sequences of the 49 cloned R genes to identify homologs across H. incana. A total of 75 cloned disease-resistance gene homologs (CDRHs) were found. Cis-acting elements (CREs) were analysed in promoter sequences of 914 RGAs in H. incana, which confirmed their potential function in disease defence. Overall, the results suggest that the wild species H. incana could be a potential R gene source for various disease resistances, including blackleg.

Blackleg is a common cause of death in cattle, mostly caused by the bacterium Clostridium chauvoei. Cardiac lesions were traditionally considered uncommon in cases of blackleg in cattle until a 2018 study reported otherwise. This study was aimed at determining the prevalence of cardiac disease among cattle that died of blackleg in Tennessee, USA. The outcome of this study would reinforce the importance of assessing cardiac lesions in suspected cases of blackleg in cattle. The University of Tennessee Veterinary Medical Center database searched for cattle with a confirmed diagnosis of blackleg necropsied between 2004 and 2018. Of the 120 necropsy reports, 37 had a diagnosis of blackleg. Histology slides of skeletal muscle (26/37) and the heart (26/37) were reviewed to confirm the presence of supportive lesions. Of the 37 cases of blackleg identified, 26 animals (70.3%) had cardiac lesions, including 4 (10.8%) that had only cardiac involvement without skeletal muscle lesions. Specifically, (5.4%; 2/37) had only necrotizing myocarditis; (13.5%; 5/37) had only fibrinous or fibrinosuppurative pericarditis, epicarditis, or endocarditis; (51.4%; 19/26) had a combination of myocarditis and pericarditis, epicarditis, or endocarditis; and (29.7%; 11/37) had no lesions. Furthermore, of the 26 cases with cardiac lesions, 24 cases had gross lesions, while 2 cases were identified only by microscopic examination. This indicates that gross examination alone is insufficient to identify cardiac involvement in blackleg cases in cattle. Contrary to traditional perceptions, cardiac lesions in cases of bovine blackleg could be as high as 70% and are most often associated with skeletal muscle lesions. The prevalence of cardiac lesions in cases of blackleg in cattle may be higher when the heart is examined microscopically than if it is only evaluated grossly. Pathologists should specifically evaluate the heart for lesions in suspected cases of blackleg in cattle and utilize microscopic examination when gross lesions are absent.

BACKGROUND: Phoma stem canker is a damaging disease of oilseed rape caused by two related fungal species, Leptosphaeria maculans and L. biglobosa. However, previous work has mainly focused on L. maculans and there has been little work on L. biglobosa. This work provides evidence of the importance of L. biglobosa to stem canker epidemics in the UK. RESULTS: Quantification of L. maculans and L. biglobosa DNA using species‐specific quantitative PCR showed that L. biglobosa caused both upper stem lesions and stem base cankers on nine oilseed rape cultivars in the UK. Upper stem lesions were mainly caused by L. biglobosa. For stem base cankers, there was more L. maculans DNA than L. biglobosa DNA in the susceptible cultivar Drakkar, while there was more L. biglobosa DNA than L. maculans DNA in cultivars with the resistance gene Rlm7 against L. maculans. The frequency of L. biglobosa detected in stem base cankers increased from 14% in 2000 to 95% in 2013. Ascospores of L. biglobosa and L. maculans were mostly released on the same days and the number of L. biglobosa ascospores in air samples increased from the 2010/2011 to 2012/2013 growing seasons. CONCLUSION: Effective control of L. maculans increased infection by L. biglobosa, causing severe upper stem lesions and stem base cankers, leading to yield losses. The importance of L. biglobosa to phoma stem canker epidemics can no longer be ignored. Effective control of phoma stem canker epidemics needs to target both L. maculans and L. biglobosa. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Canola (Brassica napus L.) production is threatened by blackleg disease caused by Leptosphaeria maculans. Disease outcome is determined by interactions among pathogens, plants, farming practices, and environmental factors. Although the gene-for-gene interactions between the pathogen and its plant host are relatively clear, how precisely the pathogen interacts with the environment and farming practices is still poorly understood, making disease forecasting challenging for commercial farmlands. In recent years, artificial intelligence (AI) has been successful in forecasting disease risks based on environmental factors. In this study, we evaluated two AI methods and a data augmentation method to forecast disease risk using a dataset collected from 116 farmlands in Alberta in 2021 and 2022. We first assessed a machine learning model (support vector machine or SVM) and a deep-learning model (convolutional neural network or CNN) to predict blackleg severity based on five weather variables, flea beetle damage, root maggot damage, and crop-rotation variables. Both SVM and CNN predicted the disease risk with an accuracy of over 66%. The data augmentation method did not improve model performance. Flea beetle feeding and maggot damage contribute little to the model's performance, and omitting these data did not appear to affect the results. In contrast, crop rotation contributes substantially to model performance. The five weather variables contribute roughly equally to the model's performance, and removing any of the individual weather variables did not impact prediction ability for both models. [ABSTRACT FROM AUTHOR]

The threat of emerging plant diseases has become more frequent as global warming and international trade are increasing. Blackleg and soft rot of potatoes caused by the group of bacteria in the family Pectobacteriaceae and the genera Dickeya and Pectobacterium are important diseases causing economic losses globally. In the European Union, they are regulated non‐quarantine pests. Five species are commonly known to cause blackleg symptoms on potatoes indistinguishable from each other. For decades, P. atrosepticum has been the classic seed potato bacterial pathogen in cool temperate climates of Europe and North America, causing blackleg disease. However, recently several new species, unknown in Northern Europe, have emerged as virulent pathogens. One of these species is D. solani. In Finland, D. solani was first found in 2004 and has been the cause of major outbreaks of blackleg in Finland for more than a decade. Currently, its incidence has declined significantly because of a stringent, concerted engagement strategy adopted to combat the pathogen that is described in detail in this article. This strategy implemented in Finland could serve as a model system to combat other emerging and re‐emerging species of Dickeya and Pectobacterium and serve as useful support information for the formulation of a policy framework for the management of emerging plant health risks. [ABSTRACT FROM AUTHOR]

Pectinolytic bacteria of the family Enterobacteriaceae, specifically Dickeya solani, are known to cause potato blackleg. This study aimed to evaluate the effectiveness of a mixture of two bacteriophages from the genus Limestonevirus in controlling Dickeya solani in both greenhouse and field trials. The potential of bacteriophages for ecological potato control was also assessed. The phages φDs3CZ and φDs20CZ were isolated from soil in the Czech Republic between 2019 and 2021. They were applied preventively and curatively as a solution on artificially wounded and inoculated seed tubers immediately prior to planting. The phage-treated variant showed a highly significant reduction in the extent of D. solani infection compared to the untreated control in both the greenhouse and field trial. The effect of the phages depended on the concentration of the solution, the rate of tuber injury, and the sequence of application. When applied preventively, the phages caused a significantly higher reduction in the rate of blackleg symptoms (86.7% and/or 87.1%) compared to the curative application (54.6 and/or 36.6%). Phages φDs3CZ and φDs20CZ showed potential for use in biological potato control against Dickeya solani. [ABSTRACT FROM AUTHOR]

Blackleg is an infectious disease caused by Clostridium chauvoei. Cardiac blackleg has been reported in ruminants as an uncommon presentation of the disease; its pathogenesis is not understood completely. We include here a literature review of cardiac blackleg and a description of 2 cases in 12-15-mo-old feedlot steers in Argentina. Fourteen of 1,190 steers died suddenly over a period of 10 d. Postmortem examinations were performed on 5 of these animals. Grossly, severe, diffuse, fibrinous pericarditis and pleuritis, multifocal necrohemorrhagic myocarditis, diffuse pulmonary congestion, mild splenomegaly, and moderate congestion of meningeal vessels were observed. No significant gross lesions were observed in the skeletal muscles of any animal. Histology was performed on 2 of the steers. The main microscopic features were necrotizing myocarditis with myriad intralesional gram-positive rods with subterminal spores plus fibrinosuppurative pericarditis and pleuritis. C. chauvoei was detected by immunohistochemistry and PCR in the myocardium of both animals. These findings confirm a diagnosis of cardiac blackleg in these 2 steers and presumptively in the other affected animals.

This article discusses a case of a young heifer that died suddenly on a farm, showing symptoms of increased respiratory rate and elevated temperature. The necropsy revealed necrohemorrhagic myocarditis and myositis, with the presence of Clostridium chauvoei, the causative agent of blackleg disease. Blackleg is a common disease in young, well-fed cattle and can cause limb weakness, fever, and muscle swelling. The article emphasizes the importance of recognizing and diagnosing blackleg in order to prevent further outbreaks. The disease is characterized by the production of toxins that lead to localized tissue damage and systemic toxemia. Vaccination is available and has been shown to be effective in protecting animals from severe clinical disease. The presence of C. chauvoei can be confirmed through various testing methods, and the spores can be transmitted through environmental exposure or contaminated feed. [Extracted from the article]

In 2012–2021, 2,030 outbreaks of acute infectious animal diseases were registered in the Republic of Kazakhstan. Among all the diseases blackleg accounted for 20.7% (421 outbreaks), which suggests that the nosological unit is of high epizootological significance among other infectious animal diseases in the country. Analysis of the blackleg outbreaks registered over the recent 10years demonstrates asignificant annual growth in the number of outbreaks (from19 to 81outbreaks) in the Republic of Kazakhstan and the disease persistence in the territory. Within the mentioned period, the average number of blackleg-infected animals per one outbreak ranged between1 and 3 animals, which proves that blackleg is anon-contagious disease. The research indicates that blackleg is a seasonal disease in the Republic of Kazakhstan with an incidence rise in autumn. The data analysis for 2012–2022 did not reveal any regular blackleg epizooties. The epizootological zoning made it possible to conclude that the blackleg situation in 6 Oblasts (which account for42.8% of the total territory) was rather tense; in 5 Oblasts (35.7% of the country’s territory) the epizootic situation was less tense and the remaining 3 Oblasts (21.5%) are disease-free. Therefore, blackleg zoning in the Republic makes it possible to use a differential approach to planning preventive veterinary and control measures, depending on the intensity of the epizootic situation. The research results will help to improve the system of blackleg surveillance, to predict the disease spread in animals and can be used to develop anti-epizootic measures.

Clostridial infections in cattle are a significant concern for Brazilian livestock. These diseases are caused by various species of Clostridium, which are known for their ability to produce potent toxins. Botulism in cattle is a serious and often fatal condition caused by the ingestion of neurotoxins produced by C. botulinum. This bacterium thrives in decomposing organic matter, such as spoiled feed, carcasses, and contaminated water. Tetanus is less common, but it is a serious disease that follows the contamination of wounds with Clostridium tetani spores. It results in muscle stiffness, spasms, and often death due to respiratory failure. Blackleg (C. chauvoei) is a disease that primarily affects young cattle, leading to acute lameness, swelling, and high fever. Malignant edema (C. septicum and others) is characterized by rapid onset of swelling at wound sites, and it can occur after injuries or surgical procedures. Enterotoxemia is triggered by the rapid growth of C. perfringens in the gut following excessive carbohydrate intake. This leads to toxin production that causes sudden death. In conclusion, clostridial bovine infections remain a persistent challenge for Brazilian cattle farmers. With continued focus on vaccination, good management practices, and research, the impact of these diseases can be minimized, safeguarding the livestock industry’s economic viability.

Soft rot Pectobacteriaceae (SRP) are the causative agents of soft rot and blackleg in potato. In this study, we investigated if potato seed lots of the same cultivar, but originating from different fields, inoculated with the same density of SRP and planted in the same field, showed differences in blackleg disease incidence. We tested if these differences were correlated with the microbial community composition in tuber, and the soil where the mother tubers were grown, as the microbiome is known to play a large role in plant disease resistance. We found that tubers from seed lots with a high disease incidence had a different microbial community composition than tubers from seed lots with a low disease incidence. Several taxa could be identified that were on average more abundant in seed lots with a low disease incidence. However, the taxa that differed in abundance were different between the two growing seasons. Most of the taxa that differed in abundance between seed lots with high and low disease incidence were also present in the soil of the fields from which the tubers originated. However, the taxa did not differ in abundance between the different fields. This raises the question as to how these taxa are recruited by the tuber. [ABSTRACT FROM AUTHOR]

A collection of isolates of the fungi Leptosphaeria maculans and L. biglobosa, which cause blackleg disease on Brassica napus (canola/oilseed rape) and other Brassicaceae species, was assembled to represent the global diversity of these pathogens and a resource for international research. The collection consists of 226 isolates (205 L. maculans and 21 L. biglobosa) from 11 countries. The genomes of all 205 L. maculans isolates were sequenced, and the distribution and identity of avirulence gene alleles were determined based on genotypic information and phenotypic reactions on B. napus lines that hosted specific resistance genes. Whilst the frequencies of some avirulence alleles were consistent across each of the regions, others differed dramatically, potentially reflecting the canola/oilseed rape cultivars grown in those countries. Analyses of the single‐nucleotide polymorphism (SNP) diversity within these L. maculans isolates revealed geographical separation of the populations. This "open access" resource provides a standardized set of isolates that can be used to define the basis for how these fungal pathogens cause disease, and as a tool for discovery of new resistance traits in Brassica species. [ABSTRACT FROM AUTHOR]

Leptosphaeria maculans is a fungal pathogen that causes blackleg disease in canola (Brassica napus), resulting in significant yield and economic losses in Canada and many parts of the world. Plant NAC transcription factors play critical roles in plant development and response to biotic or abiotic stress. In this study, we identified and characterized a BnNAC19 gene from Brassica napus. The overexpression of BnNAC19 in transgenic canola plants contributed to the improvement of seedling resistance against L. maculans. The mycelial growth of a green fluorescent protein‐tagged strain of L. maculans and production of pycnidiospores were shown to be inhibited in the transgenic canola plants overexpressing BnNAC19. In addition, the canola transgenic line overexpressing BnNAC19 showed increased disease resistance in the adult plant, which was determined by quantitative resistance. Both increased seedling and adult plant resistance in transgenic canola plants overexpressing BnNAC19 indicate that the BnNAC19 gene plays a positive role against L. maculans. The expression pattern of genes BnNAC19 upstream and downstream of BnNAC19 that participate in plant defence pathways were investigated to elucidate the B. napus resistance mechanisms to L. maculans infection, and hence to aid the long‐term blackleg disease‐resistant breeding programmes. [ABSTRACT FROM AUTHOR]

Phytopathogenic bacteria of the genus Pectobacterium are responsible for several diseases that affect potato (Solanum tuberosum L.) production worldwide, including blackleg and tuber soft rot. These bacteria are highly diverse, with over 17 different species currently identified. However, some of the recently described species, such as Pectobacterium punjabense, are still poorly understood. In this study, we focused on P. punjabense isolates collected from diseased potato tubers in Russia in 2021. Whole-genome sequencing was used to characterise the genomic diversity of the pathogen and determine the biochemical profiles of the isolated bacteria. The ability of these isolates to cause soft rot symptoms was tested. A comparative assessment of the potential pathogenicity of the Pectobacterium isolates was conducted by infecting potato tubers and measuring the accumulation of biomass in a liquid medium during cultivation at different temperatures. A TaqMan qPCR assay was developed for the highly sensitive and specific characterisation of P. punjabense strains, which can be used in diagnostic systems. This is the first report on P. punjabense causing potato disease in the Russian Federation.

Phoma stem canker (blackleg), caused by the fungi Leptosphaeria maculans (anamorph Phoma lingam) and L. biglobosa, is one of the most devastating diseases in oilseed rape (Brassica napus L.) production worldwide. However, the population structure and genetic variation of L. biglobosa populations in China have rarely been investigated. Here, a collection of 214 fungal strains of blackleg from China (including Shaanxi, Jiangxi, Hubei, Jiangsu, Chongqing, Sichuan, Guangxi, Guizhou, Hunan, and Henan) and Europe (France and Ukraine) was identified as L. biglobosa. Three simple sequence repeat (SSR) markers were developed to characterize their population structure. The results showed that the Nei's average gene diversity ranged from 0.6771 for the population from Jiangsu to 0.3009 for the population from Hunan. In addition, most of the genetic variability (96%) occurred within groups and there were only relatively small amounts among groups (4.0%) (FST = 0.043, p = 0.042 < 0.05). Pairwise population differentiation (FST) suggested that significant genetic differentiation was observed between different L. biglobosa populations. Bayesian and unweighted average method analysis revealed that these L. biglobosa strains were clustered into three branches, and three European strains were similar to those from eastern China. The pathogenicity assay showed that those in Group III were significantly more virulent than those in Group I (t = 2.69, p = 0.016). The study also showed that Group III was dominant in Chinese L. biglobosa populations, which provides new insights for the further study of population evolution and the management of this pathogen. [ABSTRACT FROM AUTHOR]

Pectobacterium and Dickeya species are pathogens of increasing importance on potatoes worldwide. These Soft Rotting Pectobacteriaceae (SRP) cause soft rot, blackleg, and aerial stem rot of tubers and plants, which can lead to extensive yield losses under conditions favourable for disease development. High priority is placed on continual, regular surveillance of Pectobacterium and Dickeya populations internationally, to ensure that new pathogens are not introduced into potato production areas. A survey was therefore undertaken to identify the primary SRP on potatoes in South Africa. Representative isolates were tested for pathogenicity and symptom expression, singly and in combination, in tuber slice assays and pot trials. Results showed that Pectobacterium brasiliense (Pb) remains the dominant and most pathogenic species in the country. The presence of Pectobacterium carotovorum (Pc) and Pectobacterium parmentieri was confirmed, although these species were far less common than Pb. Pectobacterium versatile (Pv) was reported for the first time on potatoes in South Africa. Pv caused soft rot in tuber slice assays and blackleg symptoms in pathogenicity pot trials, albeit at low incidences. Some strains identified as Pc were recently reclassified as a novel species, Pv. Pectobacterium carotovorum is more often associated with aerial stem rot than blackleg, which might explain low blackleg incidence in the trials, as well as the aerial stem rot symptoms from which the initial isolations were made. The lack of detection of Dickeya solani in any of the samples suggests that it remains absent from the country. [ABSTRACT FROM AUTHOR]

Soft rot Pectobacteriaceae (SRP), such as Pectobacterium and Dickeya, are phytopathogenic agents responsible for blackleg disease on several crops, such as potatoes, affecting the yield and depressing the seed production quality. However, neither conventional nor biocontrol products are available on the market to control this disease. In this study Pseudomonas PA14H7, a bacteria isolated from potato rhizosphere, was selected as a potential antagonist agent against Dickeya solani. In order to understand the mechanism involved in this antagonism, we managed to identify the main active molecule(s) produced by PA14H7. Cell-free supernatant (CFS) of PA14H7 cultures were extracted and analyzed using LC-MS, GC-MS, and NMR. We further correlated the biological activity against Dickeya solani of extracted CFS-PA14H7 to the presence of 7-hydroxytropolone (7-HT) complexed with iron. In a second time, we have synthesized this molecule and determined accurately using LC-UV, LC-MS, and GC-MS that, after 48 h incubation, PA14H7 released, in its CFS, around 9 mg/L of 7-HT. The biological activities of CFS-PA14H7 vs. synthetic 7-HT, at this concentration, were evaluated to have a similar bacteriostatic effect on the growth of Dickeya solani. Even if 7-HT is produced by other Pseudomonas species and is mostly known for its antibacterial and antifungal activities, this is the first description of its involvement as an effective molecule against pectinolytic bacteria. Our work opens the way for the comprehension of the mode of action of PA14H7 as a biocontrol agent against potato blackleg. [ABSTRACT FROM AUTHOR]

Blackleg disease is devastating for wasabi (Eutrema japonicum) production, occurring at any time and everywhere within the main production area of the Sichuan Province, China. There have been very few studies on the chemical control of this disease. In this study, we isolated and identified a local popular strain of the pathogen Plenodomus wasabiae. The isolated fungus strain caused typical disease spots on the leaves and rhizomes upon inoculation back to wasabi seedlings. The symptoms of blackleg disease developed very quickly, becaming visible on the second day after exposure to P. wasabiae and leading to death within one week. We then evaluated the efficacy of ten widely used fungicides to screen out effective fungicides. The efficacy of the tested fungicides was determined through mycelial growth inhibition on medium plates. As a result, tebuconazole and pyraclostrobin were able to inhibit the mycelial growth of P. wasabiae, and the most widely used dimethomorph in local production areas produced the lowest inhibition activity (13.8%). Nevertheless, the highest control efficacy of tebuconazole and pyraclostrobin on wasabi seedlings was only 47.48% and 39.03%, respectively. Generally, the control efficacy of spraying the fungicide before inoculation was better than that after inoculation. An increase in the application concentration of the two fungicides did not proportionately result in improved performance. We cloned the full-length sequence of sterol 14-demethylase (CYP51) and cytochrome B (CYTB) of which the mutations may contribute to the possible antifungalresistance. These two genes of the isolated fungus do not possess any reported mutations that lead to fungicide resistance. Previous studies indicate that there is a significant difference between fungicides in terms of the effectiveness of controlling blackleg disease; however, the control efficacy of fungicides is limited in blackleg control. Therefore, field management to prevent wound infection and unfavorable environmental conditions are more important than pesticide management. [ABSTRACT FROM AUTHOR]

Pectobacterium atrosepticum (Pba) are phytopathogenic, pectinolytic, non-sporulating, gram-negative rods causing blackleg and soft rot diseases in potato. They are ubiquitously present under temperate climate conditions and contribute to significant economic losses. Currently, there are no efficient control methods against soft rot Pectobacteriaceae (SRP). As limitation of the spread of SRP is solely prevention-based, we undertook broad characterization on both genotypic and phenotypic levels of the P. atrosepticum isolates acquired during monitoring of potato fields in Poland in 2013, 2014 and 2016. Of REP, ERIC and BOX-based genomic fingerprinting, the BOX-based approach turned out to be the most informative and allowed for classification of 118 Pba strains into six groups. The present study indicated that IV and I BOX profiles dominated among the investigated population. Finally, 23 Pba strains representing all BOX groups and originating from various growing seasons were selected for genotypic, phylogenetic and phenotypic studies. rpoS-based phylogeny revealed intraspecies variation (16 SNP sites) among the studied Pba strains, in contrast to the analyses relying on gyrA (1 SNP) and recA (0 SNP) sequences. Pba strains showed higher potency to macerate potato tissue at 20 °C than 28 °C. These isolates exhibited rather uniform production of plant cell wall degrading enzymes (pectinases, cellulases and proteases), lipases, siderophores and biofilm, however in the majority of cases inferior in comparison to Dickeya solani and Pectobacterium carotovorum strains. In conclusion, this study revealed genotypic and phenotypic uniformity in addition to high virulence potential of Pba strains isolated from potato fields during several growing seasons in Poland. [ABSTRACT FROM AUTHOR]

Pectinolytic bacteria of the family Enterobacteriaceae, specifically Dickeya solani, are known to cause potato blackleg. This study aimed to evaluate the effectiveness of a mixture of two bacteriophages from the genus Limestonevirus in controlling Dickeya solani in both greenhouse and field trials. The potential of bacteriophages for ecological potato control was also assessed. The phages φDs3CZ and φDs20CZ were isolated from soil in the Czech Republic between 2019 and 2021. They were applied preventively and curatively as a solution on artificially wounded and inoculated seed tubers immediately prior to planting. The phage-treated variant showed a highly significant reduction in the extent of D. solani infection compared to the untreated control in both the greenhouse and field trial. The effect of the phages depended on the concentration of the solution, the rate of tuber injury, and the sequence of application. When applied preventively, the phages caused a significantly higher reduction in the rate of blackleg symptoms (86.7% and/or 87.1%) compared to the curative application (54.6 and/or 36.6%). Phages φDs3CZ and φDs20CZ showed potential for use in biological potato control against Dickeya solani.

P. brasiliense is an important bacterial pathogen causing blackleg (BL) in potatoes. Nevertheless, P. brasiliense is often detected in seed lots that do not develop any of the typical blackleg symptoms in the potato crop when planted. Field bioassays identified that P. brasiliense strains can be categorized into two distinct classes, some able to cause blackleg symptoms and some unable to do it. A comparative pangenomic approach was performed on 116 P. brasiliense strains, of which 15 were characterized as BL-causing strains and 25 as non-causative. In a genetically homogeneous clade comprising all BL-causing P. brasiliense strains, two genes only present in the BL-causing strains were identified, one encoding a predicted lysozyme inhibitor Lprl (LZI) and one encoding a putative Toll/interleukin-1 receptor (TIR) domain-containing protein. TaqMan assays for the specific detection of BL-causing P. brasiliense were developed and integrated with the previously developed generic P. brasiliense assay into a triplex TaqMan assay. This simultaneous detection makes the scoring more efficient as only a single tube is needed, and it is more robust as BL-causing strains of P. brasiliense should be positive for all three assays. Individual P. brasiliense strains were found to be either positive for all three assays or only for the P. brasiliense assay. In potato samples, the mixed presence of BL-causing and not BL-causing P. brasiliense strains was observed as shown by the difference in Ct value of the TaqMan assays. However, upon extension of the number of strains, it became clear that in recent years additional BL-causing lineages of P. brasiliense were detected for which additional assays must be developed. [ABSTRACT FROM AUTHOR]

Context: Class III acyl-CoA-binding proteins such as those from dicots (Arabidopsis and grapevine) play a role in defence against biotrophic pathogens. The overexpression of the monocot Oryza sativa (rice) OsACBP5 in Arabidopsis and rice has been demonstrated to enhance broad-spectrum disease resistance against selected phytopathogens in OsACBP5-overexpressing (OsACBP5-OE) lines. Aims: We aimed to develop transgenic rapid-cycling Brassica napus (B. napus -RC) and canola cv. Westar OsACBP5-OEs using tissue culture-based Agrobacterium -mediated transformation and to evaluate transgenic plants for resistance against Alternaria blight, blackleg and Sclerotinia rot diseases. Methods: Transgenic B. napus -RC and cv. Westar OsACBP5-OEs were generated through Agrobacterium -mediated transformation using Agrobacterium strain LBA4404 harbouring a plasmid with the rice complementary DNA encoding OsACBP5 driven by the cauliflower mosaic virus 35S promoter. Alternaria blight and blackleg pathogen assays were based on infecting young cotyledons, while detached leaf assay was used to test the tolerance of B. napus plants toward Sclerotinia sclerotiorum. Key results: Average transformation efficiencies of 24.2% and 29.1% were obtained for B. napus -RC and B. napus cv. Westar cotyledons respectively. OsACBP5-OE plants exhibited resistance 5 days after inoculation with Alternaria brassicae , 12 days after inoculation with Leptosphaeria maculans , and 24 h after inoculation with S. sclerotiorum. Conclusions: Transformation of B. napus -RC was shown herein to be an effective trait testing platform for canola. This study also provides an insight into the usefulness of OsACBP5 in enhancing resistance to necrotrophic phytopathogens. Implications: OsACBP5 can be overexpressed in other crops to generate pathogen-resistant varieties. Oilseed rape is the second largest oilseed crop in the world; and with an increase in oilseed rape cultivation worldwide there is a corresponding threat of elevated disease incidences arising from various phytopathogens. Fungal pathogens pose severe threats to the yield of oilseed rape crops, whereas bacterial and viral pathogens have very little effect. In this paper, we have successfully generated transgenic oilseed rape plants that are resistant to early infection from various fungal pathogens. [ABSTRACT FROM AUTHOR]

Blackleg and aerial stem rot of potato (Solanum tuberosum L.), caused by soft rot enterobacteria of the genera Pectobacterium and Dickeya, has recently increased years in Hebei Province, China. Field surveys were performed during the 2021 potato growing season in Hebei to identify and characterize bacterial pathogens. Sixteen potato plants showing blackleg or aerial stem rot were collected from three potato-producing areas, and ten representative pectinolytic bacteria were isolated from symptomatic plants. 16S rDNA sequencing and multilocus sequence analysis were performed to determine the taxonomic position of the bacterial isolates. The isolates belonged to the genus Pectobacterium, including Pectobacterium atrosepticum, Pectobacterium carotovorum, Pectobacterium brasiliense, and Pectobacterium parmentieri. The exceptions were isolates BY21311 and BY21312, which belonged to a new species of Pectobacterium polonicum previously found in groundwater. The taxonomy of isolate BY21311 was confirmed using whole genome-based analysis. P. polonicum has only been identified in potato plants on one farm in Baoding region in China. Isolates BY21311 and BY21312 displayed similar physiological and biochemical traits to the type strain DPMP315T. Artificial inoculation assays revealed that isolate BY21311 fulfilled Koch's postulates for potato blackleg. These findings represent the first time P. polonicum, a waterassociated Pectobacterium species may be the cause of blackleg in the field. Interestingly, P. polonicum BY21311 has reduced ability to macerate potato tubers when compared to P. atrosepticum, P. brasiliense, P. versatile, and P. parvum, which is more virulent in tubers than the type strain DPMP315T. The host range of isolate BY21311 was determined by injection method, which can impregnate five plants. Although the genome of isolate BY21311 harbors gene clusters encoding a type III secretion system, it did not elicit a hypersensitive response (HR) in Nicotiana benthamiana or N. tabacum leaves. T3SS effector AvrE and T4SS effector PilN were obtained by predicting isolate BY21311 genome. P. polonicum appears to show significant variations in gene content between two genomes, and gene content varies between isolates BY21311 and DPMP315T, with strain specific-genes involved in many aspects, including lipopolysaccharide biosynthesis, substrate translocation, T4SS and T6SS among others, suggesting that isolates BY21311 and DPMP315T might represent distinct clades within the species. [ABSTRACT FROM AUTHOR]

Dickeya and Pectobacterium species are the causal agents of blackleg and soft rot diseases. This article explores the possibility of using the glycoalkaloids (GAs) naturally produced by the potato tuber after the greening process as a blackleg control method. We first tested the effect of GAs extracted from four potato cultivars on the growth and viability of one Dickeya and one Pectobacterium strain in growth media. Then, four years of field experiments were performed in which the incidence of blackleg was assessed in plants grown from the seed tubers of cv. Agria that were subjected to various greening treatments. In the growth media, all GAs isolated from the four cultivars appeared to be bacteriostatic and bactericidal against both bacteria strains. The inhibitory effect varied among GAs from different cultivars. Except for a one-year field trial, the blackleg incidence was lower in plants grown from green seed tubers without the yield being affected. The blackleg control was marginal, probably due to the low production of GAs by the tubers of cv. Agria after greening. Based on our findings, seed tuber greening has a good potential for blackleg control after the identification of varieties that present optimal GA composition after greening. [ABSTRACT FROM AUTHOR]

Pectobacterium species are one of the main bacterial agents of soft rot and blackleg diseases that cause economic damage to potato crops. Farmers around the world suffer losses from both diseases and use different strategies to control. In this study, local potato genotypes were evaluated for disease severity of soft rot and blackleg. We discovered putative genotypes with low disease severity for both diseases. In the tuber experiment, the lowest soft rot was determined for genotype 18 with 34% disease severity. The highest soft rot was found in the cultivars Natasha, Laperla and Sultanecem. In the plant experiment, the lowest lesion length was measured in the cultivars Sultannur, Orchestra and Marabel. The 33% disease severity for these cultivars was also calculated for genotypes 18 and 32. With regard to soft rot and blackleg of potato, this is the first study to determine disease severity of Turkish local potato genotypes. [ABSTRACT FROM AUTHOR]

Blackleg, caused by Leptosphaeria maculans, is an important disease of canola (Brassica napus). The pathogen can attack stems, leaves and pods, but basal stem cankers are most damaging and can result in significant yield losses. In Canada, Verticillium stripe (Verticillium longisporum) has recently emerged as another disease threat to canola. Symptoms of Verticillium stripe can resemble those of blackleg, and the two diseases may occur together. The effect of blackleg on yield was explored in field experiments with two canola hybrids and by evaluating a wider variety of hybrids in commercial crops in central Alberta, Canada. The impact on yield of L. maculans/V. longisporum interactions was also assessed under field and greenhouse conditions. In most hybrids, the relationship between blackleg severity and yield components was best explained by second-degree quadratic equations, although a linear relationship was found for one variety sampled in commercial fields. When L. maculans was co-inoculated with V. longisporum, blackleg severity and yield losses increased. In some cases, Verticillium stripe caused greater yield losses than blackleg. The results suggest that the interaction between L. maculans/V. longisporum may cause more severe losses in canola, highlighting the need for proactive disease management strategies. [ABSTRACT FROM AUTHOR]

Blackleg (Phoma) disease, caused by the ascomycete fungi Plenodomus biglobosus and P. lingam, threatens oilseed rape (OSR; Brassica napus) crops internationally. In many parts of the world, both species co-occur, but in China only P. biglobosus has so far been reported. Plenodomus biglobosus reproduces asexually (pycnidiospores), but also sexually (pseudothecia-yielding ascospores), via a heterothallic mating system requiring MAT1-1 and MAT1-2 genotypes. However, the roles of airborne ascospore inoculum in driving blackleg disease outbreaks in China are less well understood compared to elsewhere in the world. This is despite the very different agronomic cropping practices in parts of China, in which paddy rice and OSR are often grown in rotation; OSR stubble is often submerged under water for long periods potentially affecting pseudothecial development. Here, we indirectly investigate the potential role of sexual reproduction by developing new polymerase chain reaction (PCR) -based mating-type diagnostics for P. biglobosus and subsequently screening an international collection of 59 European and 157 Chinese isolates. Overall, in both Europe and China, P. biglobosus mating types did not deviate from a 1:1 ratio, such as is generally thought to occur under frequency-dependent selection in sexually reproducing pathogen populations. Both mating types were balanced in all the individual European countries tested (Austria, France, Poland, UK). Conversely, in China, mating types were only balanced in the eastern region; in the northern and southwestern regions there were skewed ratios, more typical of predominantly asexual reproduction, towards MAT1-1 and MAT1-2, respectively. The implications of these findings and future research directions for improved understanding of P. biglobosus epidemiology on OSR, particularly in China, are considered. [ABSTRACT FROM AUTHOR]

Blackleg, caused by Leptosphaeria maculans, is an important disease of canola, managed primarily through host--plant resistance. Fungal avirulence (AvrLm) genes code for effectors recognized by major host--plant resistance (Rlm) genes. AvrLm4-7 is predominant in the pathogen population in Oklahoma and Kansas, USA, and interacts with the Rlm4 and Rlm7 resistance genes. High-resolution melting analysis and sequencing were used to evaluate the genetic variability of AvrLm4-7 in avirulent (A) and virulent (a) reference isolates, and in isolates (n = 67) collected in Oklahoma from 2014 to 2017. Melting analysis of PCR products from the central primers (493 bp) and from new upstream external primers (105 bp) produced melting profiles that differed among avirulent (AvrLm4-AvrLm7 (A4A7)) and virulent (avrLm4-AvrLm7 (a4A7) and (avrLm4-avrLm7 (a4a7)) pathogen genotypes. Genotypic classification by melting analysis was supported by pathogenicity scores on seedling cotyledons of susceptible, Rlm4, and Rlm7 differentials. All of the local isolates were a4A7 genotypes. In the sequences of a4A7 reference isolates, all showed the expected mutation at bp 358 of C to G resulting in virulence on Rlm4, and silent mutations of either C to T at bp 256 or A to G at bp 134. These two haplotypes displayed unique melting profiles from the central primers in 64% and 36% of local isolates, respectively. Only the central primers produced pathotype-specific melting curves. Sustainable deployment of Rlm7 canola is needed for effective management of blackleg in the region. High-resolution melting will be useful to monitor allelic variability in AvrLm4-7 and for rapid detection of a4a7 strains. [ABSTRACT FROM AUTHOR]

Blackleg is a major fungal disease of canola caused by Leptosphaeria maculans. Due to the breakdown of current host resistance, having an effective fungicide to avoid seedling infection is important to avoid disease. Pydiflumetofen is a newly developed broad‐spectrum seed treatment fungicide in the succinate dehydrogenase inhibitor (SDHI) group. We evaluated the separate and combined application of pydiflumetofen and Vibrance Flexi on early‐season control of blackleg using moderately resistant canola cultivar SY4135 and susceptible cultivar Westar. In the greenhouse, seedlings inoculated with green fluorescent protein (GFP)‐tagged L. maculans showed lesion development and apoplastic mycelial growth in cotyledons in control and Vibrance Flexi treatments but no lesion development or in planta mycelial growth was observed in pydiflumetofen‐treated seedlings, in Westar or SY4135, 14 days postinoculation. SY4135 and Westar plants with pydiflumetofen‐treated seeds inoculated with L. maculans isolate D3 had significantly lower disease severity. Both host genotypes treated with pydiflumetofen showed lower disease severity estimates than the other treatments. Statistically significant disease severity reduction was cultivar dependent in the field. Canola is most susceptible to blackleg as a seedling, from the cotyledon to two‐ to four‐leaf stage. Pydiflumetofen protects the plant at the critical window for infection. Therefore, pydiflumetofen could be a potential tool that farmers can add to their blackleg management toolbox. [ABSTRACT FROM AUTHOR]

Hybridization of Brassica napus with various Brassicaceae species can result in obtaining new forms with increased resistance to blackleg, a dangerous disease caused mainly by Leptosphaeria maculans. In this study, we aimed to correlate the field resistance of selected Brassica hybrids to blackleg with chromosomal structure revealed by Fluorescence in situ hybridization. Tested genotypes varied in the number of chromosomes and rDNA signals. The greatest variation was observed for A1-type chromosomes. Field evaluation also revealed significant differences in L. maculans resistance. Performed analyses allowed to distinguish three B. napus × Brassica fruticulosa genotypes in which variable patterns of chromosomal structure might be connected to field resistance. However, a more thorough study, including the detection of all A-genome chromosomes, is required.

Quantitative polymerase chain reaction (qPCR) is a commonly used technique for plant disease diagnosis, which generally requires DNA extraction from the plant samples. The efficiency of DNA extraction has a significant influence on the accuracy of qPCR. Thus, including a DNA extraction efficiency control is important in qPCR analyses. To develop and evaluate a DNA extraction efficiency control, a Stagonospora nodorum (syn. Phaeosphaeria nodorum , synonym and correct taxonomic name: Parastagonospora nodorum) strain named HUA-22 was created by transferring a green florescent protein (GFP) gene into the genome of the S. nodorum strain Sn15. HUA-22 showed a similar pathogenicity as Sn15 but carried a strong GFP activity. A qPCR primers/probe set named P-GFP, targeting the GFP sequence, was designed. Using P-GFP, qPCR analysis was conducted on DNA extracted from replicated samples of HUA-22 conidia, and confirmed that HUA-22 could be used to characterize the variation in replicated DNA extractions. Conidia of HUA-22 were used to spike soil samples inoculated with the canola clubroot pathogen Plasmodiophora brassicae , canola stem samples infected with the blackleg pathogens Leptosphaeria biglobosa and/or L. maculans and wheat/barley samples infected with Xanthomonas translucens pv. translucens (Xtt) or X. translucens pv. undulosa (Xtu). Duplex qPCR using P-GFP and a primers/probe set specific to P. brassicae , triplex qPCR using P-GFP and primers/probe sets specific to L. biglobosa and L. maculans , and triplex qPCR using P-GFP and primers/probe sets specific to Xtt and Xtu were conducted. The results indicated that HUA-22 could be used as a standard for DNA extraction efficiency in qPCR-based plant disease diagnosis. Adding HUA-22 conidia to plant or soil samples prior to DNA extraction, and subsequent use of the P-GFP detection control, provided an added control that could distinguish truly negative from false-negative qPCR results. • A GFP -labeled S. nodorum strain named HUA-22 was created by transformation. • GFP in HUA-22 can be used as a DNA control in qPCR diagnosis of plant diseases. • HUA-22 was tested in the diagnosis of plant diseases caused by five pathogens. [ABSTRACT FROM AUTHOR]

Phoma stem canker (blackleg), caused by the fungi Leptosphaeria maculans (anamorph Phoma lingam) and L. biglobosa, is one of the most devastating diseases in oilseed rape (Brassica napus L.) production worldwide. However, the population structure and genetic variation of L. biglobosa populations in China have rarely been investigated. Here, a collection of 214 fungal strains of blackleg from China (including Shaanxi, Jiangxi, Hubei, Jiangsu, Chongqing, Sichuan, Guangxi, Guizhou, Hunan, and Henan) and Europe (France and Ukraine) was identified as L. biglobosa. Three simple sequence repeat (SSR) markers were developed to characterize their population structure. The results showed that the Nei’s average gene diversity ranged from 0.6771 for the population from Jiangsu to 0.3009 for the population from Hunan. In addition, most of the genetic variability (96%) occurred within groups and there were only relatively small amounts among groups (4.0%) (FST = 0.043, p = 0.042 < 0.05). Pairwise population differentiation (FST) suggested that significant genetic differentiation was observed between different L. biglobosa populations. Bayesian and unweighted average method analysis revealed that these L. biglobosa strains were clustered into three branches, and three European strains were similar to those from eastern China. The pathogenicity assay showed that those in Group III were significantly more virulent than those in Group I (t = 2.69, p = 0.016). The study also showed that Group III was dominant in Chinese L. biglobosa populations, which provides new insights for the further study of population evolution and the management of this pathogen.

Blackleg disease is devastating for wasabi (Eutrema japonicum) production, occurring at any time and everywhere within the main production area of the Sichuan Province, China. There have been very few studies on the chemical control of this disease. In this study, we isolated and identified a local popular strain of the pathogen Plenodomus wasabiae. The isolated fungus strain caused typical disease spots on the leaves and rhizomes upon inoculation back to wasabi seedlings. The symptoms of blackleg disease developed very quickly, becaming visible on the second day after exposure to P. wasabiae and leading to death within one week. We then evaluated the efficacy of ten widely used fungicides to screen out effective fungicides. The efficacy of the tested fungicides was determined through mycelial growth inhibition on medium plates. As a result, tebuconazole and pyraclostrobin were able to inhibit the mycelial growth of P. wasabiae, and the most widely used dimethomorph in local production areas produced the lowest inhibition activity (13.8%). Nevertheless, the highest control efficacy of tebuconazole and pyraclostrobin on wasabi seedlings was only 47.48% and 39.03%, respectively. Generally, the control efficacy of spraying the fungicide before inoculation was better than that after inoculation. An increase in the application concentration of the two fungicides did not proportionately result in improved performance. We cloned the full-length sequence of sterol 14-demethylase (CYP51) and cytochrome B (CYTB) of which the mutations may contribute to the possible antifungalresistance. These two genes of the isolated fungus do not possess any reported mutations that lead to fungicide resistance. Previous studies indicate that there is a significant difference between fungicides in terms of the effectiveness of controlling blackleg disease; however, the control efficacy of fungicides is limited in blackleg control. Therefore, field management to prevent wound infection and unfavorable environmental conditions are more important than pesticide management.

Blackleg is an infectious disease of cattle and rarely other ruminants, produced by Clostridium chauvoei and characterized by necrotizing myositis. In most cases of blackleg, the large muscles of the pectoral and pelvic girdles are affected, with other skeletal muscles and the heart involved less frequently. We studied 29 blackleg cases selected from the archives of the California Animal Health and Food Safety Laboratory, 1991-2015. Immunohistochemistry was also evaluated to detect C. chauvoei in formalin-fixed, paraffin-embedded (FFPE) tissues of cattle. Nineteen animals had gross and/or microscopic lesions in both skeletal muscle and heart, 9 had lesions in the skeletal musculature alone, and 1 in the heart alone. Gross lesions in the skeletal musculature involved the following muscle groups: hindquarters ( n = 8), forequarters ( n = 5), neck ( n = 5), lumbar area ( n = 3), brisket ( n = 2), diaphragm ( n = 2), abdominal wall ( n = 1), thoracic wall ( n = 1), and tongue ( n = 1). Of the 20 animals that had lesions in the heart, 11 had pericarditis and myocarditis; 7 had pericarditis, myocarditis, and endocarditis; and 1 each had pericarditis and myocarditis. Immunohistochemistry was 100% sensitive to detect C. chauvoei in FFPE skeletal muscle and/or heart of cattle with blackleg. Simultaneous lesions in skeletal musculature and heart were relatively common in blackleg cases in California; the most affected skeletal muscles were those of the hindlimbs.

Abstract Background The native potatoes (Solanum tuberosum subsp. tuberosum L.) grown in Chile (Chiloé) represent a new, unexplored source of endophytes to find potential biological control agents for the prevention of bacterial diseases, like blackleg and soft rot, in potato crops. Result The objective of this study was the selection of endophytic actinobacteria from native potatoes for antagonistic activity against Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum, and their potential to suppress tissue maceration symptoms in potato tubers. This potential was determined through the quorum quenching activity using a Chromobacterium violaceaum ATCC 12472 Wild type (WT) bioassay and its colonization behavior of the potato plant root system (S. tuberosum) by means of the Double labeling of oligonucleotide probes for fluorescence in situ hybridization (DOPE-FISH) targeting technique. The results showed that although Streptomyces sp. TP199 and Streptomyces sp. A2R31 were able to inhibit the growth of the pathogens, only the Streptomyces sp. TP199 isolate inhibited Pectobacterium sp. growth and diminished tissue maceration in tubers (p ≤ 0.05). Streptomyces sp. TP199 had metal-dependent acyl homoserine lactones (AHL) quorum quenching activity in vitro and was able to colonize the root endosphere 10 days after inoculation. Conclusions We concluded that native potatoes from southern Chile possess endophyte actinobacteria that are potential agents for the disease management of soft rot and blackleg.

Blackleg, caused by the fungus Leptosphaeria maculans, is an important disease of canola. Both ascospores and pycnidiospores of the fungus can infect intact leaves under conditions of extended leaf wetness, with infection then progressing further into the stem. In western Canada, spring is typically cool and dry and additional factors may be involved for successful infection. This study was designed to assess the effect of wounding and wound age on cotyledon infection, to evaluate the likelihood that flea beetle-feeding injuries could contribute to increased disease. Infection of canola cotyledons occurred readily via mechanical wounds in the absence of leaf wetness when seedlings were spray inoculated with pycnidiospores of L. maculans, whereas no infection occurred on intact cotyledons even under 6-h leaf wetness. Wound age also played a role in susceptibility; wounded tissues were less susceptible when plants were kept in a greenhouse for 8 h or longer before inoculation, with substantially reduced infection success relative to fresh wounds. This wound-age effect was similar on susceptible and resistant canola varieties. A high temperature (25°C) seemed to favour the healing of wounds, reducing susceptibility when compared with control (21/16°C) and low (10°C) temperatures. Leaf wetness post-wounding may hinder healing, and high post-inoculation humidity (80–90% relative humidity) increased infection via older wounds slightly, relative to lower (50–60%) relative humidity. These data provide a rationale for studying the effect of improved flea beetle control on early L. maculans infection of canola. [ABSTRACT FROM AUTHOR]

Pectobacterium is a diverse genus which comprises of multiple destructive bacterial species which cause soft rot/blackleg/wilt disease complex in a wide variety of crops by employing high levels of virulence factors. During the 2018, 2019 and 2020 potato growing seasons, numerous outbreaks of bacterial wilt, stem blackleg and tuber soft rot were recorded, and symptomatic plant samples from ten localities in the Province of Vojvodina (Serbia) were collected and analysed. Bacterial soft-rot pathogens were detected in 63 samples using genus and species-specific primers. Through 16S rRNA Sanger sequencing of 19 representative isolates, the identity of P. brasiliense (73.7%), P. punjabense (15.8%), and P. carotovorum (10.5%) species were revealed. To further validate the identification, genotypic profiling of Pectobacterium strains using rep-PCR (ERIC, BOX, REP) was conducted for 25 selected isolates and the phylogenetic assessment based on four selected housekeeping genes (gyrA, recA, rpoA, and rpoS). Physiological and biochemical properties were analysed using basic microbiological tests and VITEK® 2 GN card, and pathogenicity was confirmed on cv. VR808 and cv. Desiree potato tubers and plants. This study confirmed the distinctiveness of the newly described P. punjabense in Serbia as well as the high diversity of Pectobacterium brasiliense and Pectobacterium carotovorum species in Serbia. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum) is grown in Ecuador's Andean region at altitudes from 2,200 to 3,600 m.a.s.l., and the most commercially significant cultivar is Superchola, which constitutes 60% of total production, covering around 11,000 hectares (MAG, s.f. 2022). From November 2022 to January 2023, dark, water-soaked lesions progressing upwards from the base of the stems were observed on Superchola potato plants in Cañar, Ecuador (2°23'56.4''S 78°59'13.2''W). Approximately 20 plants in a hectare showed symptoms. Symptomatic stems from five plants were collected, surface-disinfected with 2% sodium hypochlorite, followed by 70% ethanol, and thoroughly rinsed with sterile distilled water. Plant tissue sections (1 cm²) were homogenized in 10 mM MgCl₂, serially diluted, and plated on Tryptic Soy Agar (TSA). After 48 hours of incubation at 28°C, creamy-white, yellowish, and white round colonies appeared. Streak plating was performed, yielding 14 purified bacterial isolates named M1 to M14. For the pathogenicity tests, each purified isolate was inoculated into healthy potato tubers and stem pieces (5 cm) using the prick inoculation method described by Ma et al. (2018) with modifications. Surface-sterilized tubers and stems were wounded using autoclaved toothpicks, into which 5µl of a bacterial suspension, carrying ~1 x 106 CFU/ml of bacteria per strain, was deposited into a 5 mm deep wound. Three independent replicates were conducted. Only one isolate, designated as M3, presented maceration on potato tubers, and dark, watered-soaked lesions appeared on the stem 48 h post-inoculation with strain. Other bacterial isolates showed no symptoms in either stems or tubers. Pathogenicity tests were confirmed on healthy, 4-week-old potato plants grown in a 50% perlite and 50% peat moss substrate. Inoculations were done using two methods: (1) toothpick piercing, where 5 µl of saline solution containing ~1 x 106 CFU/ml of bacteria was applied to a wound approximately 5mm deep (Ma et al. 2018), and (2) immersion of the plant foliage in a bacterial suspension of 1x 108 CFU/ml in saline solution for 10 min Controls used bacteria-free toothpicks (wounded) and sterile 10 mM MgCl₂ solution (unwounded). Plants were enclosed in plastic containers to maintain high humidity and grown at 15/25°C (day/night) with a 12 h photoperiod. Five days post-inoculation, blackleg symptoms were observed in the stems of the infected area, which turned black and rotten (wounded and unwounded). In all cases, negative controls remained symptomless. To complete Koch's postulates, bacteria were reisolated from symptomatic potato stems and showed the same morphology. To identify the isolate M3, whole genome sequencing using Oxford Nanopore technology was performed. Three marker genes were extracted, and a 5,734-bp sequence was concatenated from dnaX (2073 bp), recA (1,074bp), and leuS (2,583bp) (GenBank accession nos. PQ177849, PQ177847 and PQ177848, respectively). The concatenated sequences of M3 and type strains were used to construct a multilocus Bayesian inference phylogenetic tree using BEAST version 1.8.4. Isolate M3 grouped with Pectobacterium peruviense, showing a 100% sequence identity with the type strain P. peruviense IFB5232(Drummond et al. 2012; Portier et al. 2019; Toth et al. 2021; Waleron et al. 2018). To our knowledge, this is the first report of P. peruviense causing blackleg and soft rot in potato plants in Ecuador. Further research is essential, but this information could assist in monitoring the pathogen's spread and developing disease management strategies.

Management of plant disease in agro-ecosystems ideally relies on a combination of host genetic resistance, chemical control, and cultural practices. Growers increasingly rely on chemical and genetic options, but their relative benefits in disease control, yield, and economic outcomes are rarely quantified. We explore this relationship for blackleg crown canker disease (caused by Leptosphaeria maculans ), a major biotic constraint limiting canola production globally. Data from 20 field trials conducted from 2013 to 2015 in canola-growing regions of Australia were used to assess the effects of host resistance and fungicide treatment on blackleg severity, grain yield, and gross margin. In the absence of fungicide, blackleg disease was 88% lower in the most resistant compared with the most susceptible blackleg resistance category. In the most susceptible resistance category, the most effective fungicide treatment significantly reduced blackleg severity (from 50 to 6%) and increased grain yield (478 kg/ha, 41%) and gross margin (AU$120/ha, 17%). However, the mean benefits of fungicide tended to decrease with increasing levels of genetic resistance, to the point that yield, disease, and gross margin benefits were close to zero in the most resistant cultivars. Overall, these findings suggest that fungicides can reduce blackleg severity, but the benefits of application strongly depend on associated levels of genetic resistance. Canola cultivars with higher genetic resistance reliably reduced blackleg disease and maintained grain yield without the associated cost of fungicide application. The intensification of canola production to meet increasing global demand will require strategies to sustainably manage and protect finite genetic resistance resources to control blackleg disease., Competing Interests: The author(s) declare no conflict of interest.

Pectobacterium atrosepticum is a narrow-host-range, pectinolytic, plant-pathogenic bacterium causing blackleg of potato (Solanum tuberosum L.) worldwide. Till present, several P. atrosepticum genomes have been sequenced and characterized in detail; however, all of these genomes have come from P. atrosepticum isolates from plants grown in temperate zones, not from hosts cultivated under different climatic conditions. Herewith, we present the first complete, high-quality genome of the P. atrosepticum strain Green1 isolated from potato plants grown under a subarctic climate in Greenland. The genome of P. atrosepticum strain Green1 consists of one chromosome of 4,959,719 bp, with a GC content of 51% and no plasmids. The genome contains 4,531 annotated features, including 4,179 protein-coding genes, 22 ribosomal RNA genes, 70 transfer RNA genes, 8 noncoding RNA genes, 2 CRISPRs, and 126 pseudogenes. We believe that the information in this first high-quality, complete, closed genome of P. atrosepticum strains isolated from host plants grown in a subarctic agricultural region will provide resources for comparative genomic studies and for analyses targeting climatic adaptation and ecological fitness mechanisms present in P. atrosepticum.[Graphic: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.