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Amy O Charkowski - One of the best experts on this subject based on the ideXlab platform.
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The Changing Face of Bacterial Soft-Rot Diseases
Annual review of phytopathology, 2018Co-Authors: Amy O CharkowskiAbstract:Bacterial Soft Rot is a disease complex caused by multiple genera of gram-negative and gram-positive bacteria, with Dickeya and Pectobacterium being the most widely studied Soft-Rot bacterial pathogens. In addition to Soft Rot, these bacteria also cause blackleg of potato, foot Rot of rice, and bleeding canker of pear. Multiple Dickeya and Pectobacterium species cause the same symptoms on potato, complicating epidemiology and disease resistance studies. The primary pathogen species present in potato-growing regions differs over time and space, further complicating disease management. Genomics technologies are providing new management possibilities, including improved detection and biocontrol methods that may finally allow effective disease management. The recent development of inbred diploid potato lines is also having a major impact on studying Soft-Rot pathogens because it is now possible to study Soft-Rot disease in model plant species that produce starchy vegetative storage organs. Together, these new...
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genomics of plant associated bacteria the Soft Rot enterobacteriaceae
2014Co-Authors: Amy O Charkowski, Jenna Lind, Isael RubiosalazarAbstract:The Soft Rot Enterobacteriaceae (SRE), which includes the two genera Pectobacterium and Dickeya, are broad host range pathogens that cause wilt and Rot diseases on monocot and dicot plant hosts worldwide. These bacterial pathogens secrete high amounts of plant-cell-wall-degrading enzymes (PCWDE), such as pectinases and polygalacturonases, that digest plant cell walls and cause the Soft Rot symptoms characteristic of the SRE. The SRE can also colonize insects, and some strains are also insect pathogens. Genome sequences of a few dozen SRE strains are available, and these sequences have hastened discovery of SRE the role that many attributes play in virulence, including adhesins, toxins, volatile compounds, and contact-dependent secretion systems. Genomic and gene expression analyses have changed the view of the SRE from simple brute force pathogens to that of sophisticated pathogens that use intricately regulated gene clusters to colonize plants. Gene expression experiments also show that even though important regulatory pRoteins are conserved among the SRE, these pRoteins may not play the same regulatory roles in different SRE species. For example, only some SRE rely upon acyl-homoserine lactone (AHL)-based quorum sensing for regulation of pathogenesis genes, and SRE responses to oxygen limitation vary between Pectobacterium and Dickeya. Although there are many examples of resistance to the SRE, little effort has been made toward understanding how plants resist bacterial Soft Rot diseases. The realization that the SRE require more than pectinase production for disease may lead to increased interest in discovering plant mechanisms used to resist SRE pathogens.
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Soft Rot disease severity is affected by potato physiology and pectobacterium taxa
Plant Disease, 2011Co-Authors: Maria Del Pilar Marquezvillavicencio, Russell L Groves, Amy O CharkowskiAbstract:Marquez-Villavicencio, M. D. P., Groves, R. L., and Charkowski, A. O. 2011. Soft Rot disease severity is affected by potato physiology and Pectobacterium taxa. Plant Dis. 95:232-241. Pectobacterium species cause disease worldwide in many crop and ornamental plants, including potato. A new Pectobacterium subspecies, P. caRotovorum subsp. brasiliensis was recently described in Brazil and later found in the United States, Israel, and South Africa. Its virulence traits and host range remain unknown. A comparison of three taxa commonly found on potato showed that both P. caRotovorum subsp. caRotovorum and subsp. brasiliensis are more aggressive in causing tuber and stem Soft Rot than P. atrosepticum. Also, despite bacterial growth inhibition in vitro of P. caRotovorum subsp. caRotovorum and P. atrosepticum strains by P. caRotovorum subsp. brasiliensis, this new subspecies and P. caRotovorum subsp. caRotovorum are able to co-colonize in the same infected tissue. Both subspecies were motile in lesions. Pathogenesis assays showed that host ranges of all three overlap, but are not identical. The host ranges of individual strains of P. caRotovorum subsp. caRotovorum and subsp. brasiliensis are limited, whereas P. atrosepticum can macerate many plant species in addition to potato. There was high variability in virulence assays with potato tuber; thus physiological factors were investigated. Tuber size, maturity, and field location had significant effects on susceptibility to Soft Rot, with larger, more mature tubers being more susceptible. The enterobacterial plant pathogen Pectobacterium (formerly Erwinia caRotovora) causes Soft Rot diseases in monocot and dicot host plants in at least 35% of angiosperms (28). In potato, Pectobacterium causes wilt, Soft Rot, and blackleg and affects plant health during field production and storage (39,40). Tuber Soft Rot and aerial stem Rot often occur after plants are wounded, and tuber Soft Rot is promoted by low oxygen conditions (6,29). In contrast, blackleg is considered a tuber-borne disease, with the bacterial pathogen causing an inky black decay on the lower part of the potato stem (40). Copper sprays may be used to prevent infection of wounded plant stems and leaves, but once the plant is colonized, there is no chemical control available for this pathogen (11). Resistance genes active against Pectobacterium have been found in multiple host species, but their sequences and mechanisms remain unknown (23–25,33,43,45,50,53,57). No currently grown commercial potato variety has an effective level of resistance to Soft Rot, stem Rot, or blackleg. Pectobacterium pathogenesis has been studied for over a century (19). To promote Rot, Soft Rot pathogens employ a wide range of plant cell wall degrading enzymes to disrupt and metabolize plant cells (1,48). Additional virulence determinants also have been described as contributing to bacterial invasion, establishment, multiplication, and host resistance evasion. These include the flagellar system (36), putative phytotoxins (3), quorum-sensing system (26,41,44), efflux pumps (51), the type III secretion system (16,54), and plant antimicrobial resistance systems (27). Conducive environmental factors are also critical for the infection proc
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The Soft Rot Erwinia
Plant-Associated Bacteria, 1Co-Authors: Amy O CharkowskiAbstract:The Soft Rot Erwinia are members of the most studied bacterial family, the Enterobacteriaceae, which also includes other important plant and animal pathogens such as Pantoea, Escherichia, Salmonella, Klebsiella, and Yersinia species. Plant pathologists have been studying the Soft Rot Erwinia for nearly 120 years and published thousands of pages on this pathogen. Because the Soft Rot Erwinia are amenable to genetic manipulation and because they are wide spread in the environment, they serve as an important model for studying the ecology and evolution of enterobacterial pathogenesis. 1. TAXONOMY OF THE Soft Rot ERWINIA "The correct name of the blackleg pathogen has been the subject of much discussion and the cause of considerable confusion" Leach, 1931.
Lina M. Quesada-ocampo - One of the best experts on this subject based on the ideXlab platform.
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Cultural, Chemical, and Alternative Control Strategies for Rhizopus Soft Rot of Sweetpotato.
Plant disease, 2016Co-Authors: A. C. Scruggs, Lina M. Quesada-ocampoAbstract:Rhizopus Soft Rot, caused primarily by Rhizopus stolonifer, is one of the most common postharvest diseases of sweetpotato and is often considered the most devastating. Traditionally, Rhizopus Soft Rot has been effectively controlled using postharvest dips in dicloran fungicides; however, due to changes in market preferences, use of these fungicides is now limited. This, along with the lack of labeled and effective fungicides for control of Rhizopus Soft Rot in sweetpotato, creates the need for integrated strategies to control the disease. The effects of storage temperature (13, 23, and 29°C), relative humidity (80, 90, and 100%), and initial inoculum levels (3-, 5-, and 7-mm-diameter mycelial plugs) on progression of Rhizopus Soft Rot in 'Covington' sweetpotato were examined. Percent decay due to Rhizopus Soft Rot infection was significantly reduced (P 0.05). Sporulation of R. stolonifer was also significantly reduced at the lowest temperature of 13°C. High relative humidity (>95%) significantly increased sporulation of R. stolonifer and sporulation also increased as initial inoculum level increased. Efficacy of chlorine dioxide (ClO2) fumigation, UV-C irradiation, and postharvest dips in alternative control products were also investigated for control of Rhizopus Soft Rot. Static ClO2 treatments were effective in reducing sporulation on treated roots but had no significant impact on incidence of Rhizopus Soft Rot. UV irradiation at 3.24 KJ/m2 1 h after inoculation as well as dips in aqueous ClO2 and StorOx 2.0 significantly (P < 0.05) reduced disease incidence. Understanding the epidemiological factors favoring Rhizopus Soft Rot and identifying alternative control strategies allow for improved recommendations to limit postharvest losses in sweetpotato.
A. C. Scruggs - One of the best experts on this subject based on the ideXlab platform.
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Cultural, Chemical, and Alternative Control Strategies for Rhizopus Soft Rot of Sweetpotato.
Plant disease, 2016Co-Authors: A. C. Scruggs, Lina M. Quesada-ocampoAbstract:Rhizopus Soft Rot, caused primarily by Rhizopus stolonifer, is one of the most common postharvest diseases of sweetpotato and is often considered the most devastating. Traditionally, Rhizopus Soft Rot has been effectively controlled using postharvest dips in dicloran fungicides; however, due to changes in market preferences, use of these fungicides is now limited. This, along with the lack of labeled and effective fungicides for control of Rhizopus Soft Rot in sweetpotato, creates the need for integrated strategies to control the disease. The effects of storage temperature (13, 23, and 29°C), relative humidity (80, 90, and 100%), and initial inoculum levels (3-, 5-, and 7-mm-diameter mycelial plugs) on progression of Rhizopus Soft Rot in 'Covington' sweetpotato were examined. Percent decay due to Rhizopus Soft Rot infection was significantly reduced (P 0.05). Sporulation of R. stolonifer was also significantly reduced at the lowest temperature of 13°C. High relative humidity (>95%) significantly increased sporulation of R. stolonifer and sporulation also increased as initial inoculum level increased. Efficacy of chlorine dioxide (ClO2) fumigation, UV-C irradiation, and postharvest dips in alternative control products were also investigated for control of Rhizopus Soft Rot. Static ClO2 treatments were effective in reducing sporulation on treated roots but had no significant impact on incidence of Rhizopus Soft Rot. UV irradiation at 3.24 KJ/m2 1 h after inoculation as well as dips in aqueous ClO2 and StorOx 2.0 significantly (P < 0.05) reduced disease incidence. Understanding the epidemiological factors favoring Rhizopus Soft Rot and identifying alternative control strategies allow for improved recommendations to limit postharvest losses in sweetpotato.
Safa Abdel-kader Mohamed Hamed - One of the best experts on this subject based on the ideXlab platform.
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In-vitro studies on wood degradation in soil by Soft-Rot fungi: Aspergillus niger and Penicillium chrysogenum
International Biodeterioration & Biodegradation, 2013Co-Authors: Safa Abdel-kader Mohamed HamedAbstract:Abstract This paper focuses on the biodegradation of wood by two Soft-Rot fungi, Aspergillus niger and Penicillium chrysogenum, in soil which was artificially infested. The structural changes of pine and sycamore wood were evaluated by scanning electron microscope (SEM). Surprisingly, Soft-Rot fungi tolerate low moisture to cause extensive decay in the wood samples. The micrographs showed differences in hyphae colonization and wood degradation patterns between Soft-Rot species under this study; A. niger produced Soft-Rot decay type I (cavity formation) and Soft-Rot decay type II (erosion), while P. chrysogenum caused only Soft-Rot decay type II.
C. J. K. Wang - One of the best experts on this subject based on the ideXlab platform.
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Diffuse cavity formation in Soft Rot of
1994Co-Authors: S. E. Anagnost, J. J. Worrall, C. J. K. WangAbstract:Summary A new type of Soft Rot of southern pine longitudinal tracheids is described. In this type, Soft-Rot cavities form by diffuse degradation of the $2 cell wall layer by hyphae growing within the cell wall. Cavity formation is diffuse and irregular as opposed to the restricted, periodic cavity formation typical of type i Soft Rot. Proboscis hyphae are small (diameter 0.6 to 0.9 gm) and rapidly autolyse. These proboscis hyphae are not easily recognizable with light microscopy, especially at later stages of decay, but require transmission electron microscopy to confirm their presence. This may be an alternative interpretation of the type 2 Soft Rot of Softwoods described previously as being caused by lumenal hyphae through an intact $3. Chemical analysis of pine test blocks revealed a greater loss of glucose and an increase of galactose with diffuse type i species compared to typical type 1 Soft Rot species. The term "diffuse type 1" is suggested to describe this Soft Rot.
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Diffuse cavity formation in Soft Rot of pine
Wood Science and Technology, 1994Co-Authors: S. E. Anagnost, J. J. Worrall, C. J. K. WangAbstract:A new type of Soft Rot of southern pine longitudinal tracheids is described. In this type, Soft-Rot cavities form by diffuse degradation of the S2 cell wall layer by hyphae growing within the cell wall. Cavity formation is diffuse and irregular as opposed to the restricted, periodic cavity formation typical of type 1 Soft Rot. Proboscis hyphae are small (diameter 0.6 to 0.9 μm) and rapidly autolyse. These proboscis hyphae are not easily recognizable with light microscopy, especially at later stages of decay, but require transmission electron microscopy to confirm their presence. This may be an alternative interpretation of the type 2 Soft Rot of Softwoods described previously as being caused by lumenal hyphae through an intact S3. Chemical analysis of pine test blocks revealed a greater loss of glucose and an increase of galactose with diffuse type 1 species compared to typical type 1 Soft Rot species. The term “diffuse type 1” is suggested to describe this Soft Rot.
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Soft Rot decay capabilities and interactions of fungi and bacteria from fumigated utility poles
1992Co-Authors: C. J. K. WangAbstract:The objectives were to (1) identify microfungi and bacterial associates isolated from fumigated southern pine poles from EPRI project RP 1471-72, (2) study the Soft-Rot capabilities of predominant fungi, and (3) study interactions among microorganisms in relation to wood decay. Methods for identification followed standard techniques using morphological and physiological criteria. Soft-Rot by microfungi alone and with bacteria was determined as weight loss and anatomical examination of wood blocks using light microscopy and limited electron microscopy. Acinetobacter calcoaceticus was the predominant bacterium. Twenty-one species of microfungi were identified including four new species. A book entitled IDENTIFICATION MANUAL FOR FUNGI FROM UTILITY POLES IN THE EASTERN UNITED STATES was published. An improved Soft-Rot test was devised. Fifty-one of 84 species (60%) of microfungi from poles tested were Soft-Rot positive; that is much greater than previously reported. Three types of anatomical damage of wood of pine or birch caused by Soft-Rot fungi were described. Interaction tests showed that, in some cases, there was a strong synergism between bacteria and fungi in causing weight loss, but results were inconsistent. Although Soft Rot is often most apparent under conditions of very high moisture, intermediate moisture levels appear to be optimal, as with basidiomycete decayers.
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Importance and mobilization of nutrients in Soft Rot of wood
Canadian Journal of Microbiology, 1991Co-Authors: James J. Worrall, C. J. K. WangAbstract:Soft Rot of wood by Chaetomium globosum and Scytalidium lignicola was negligible in the absence of added nutrients. Independently varying the concentrations of nutrients in double Abrams' solution (which is often used for testing Soft Rot of wood) showed that these concentrations are higher than necessary, and in some cases supraoptimal, for Soft Rot as measured by weight loss. Optimal nutrient concentrations were lower in cases of low decay capacity than in cases of high decay capacity. A suitable, reduced solution contained, per litre, 1.5 g NH4NO3, 2.5 g KH2PO4, 2.0 g K2HPO4, and 1 g MgSO4∙7H2O. Best results were obtained when blocks were infiltrated with the solution. Increasing osmolality with KCl inhibited Soft Rot, suggesting that the solution satisfies specific nutrient requirements rather than an osmophilic requirement. P and especially N were actively mobilized into decaying blocks. As any of the nutrients were added at low levels to the external solution, decay and the influx of N increased. Ke...
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Conditions for Soft Rot of wood
Canadian Journal of Microbiology, 1991Co-Authors: J. J. Worrall, S. E. Anagnost, C. J. K. WangAbstract:Conditions leading to optimal development of Soft Rot of wood were studied in vitro. Rates of weight loss generally remained more or less constant for 12 weeks, after which they decreased. Use of Petri dishes as decay chambers, saturation of blocks with a reduced nutrient solution containing micronutrients and vitamins, and use of a thick nylon mesh as a support between the agar and blocks generally gave better results than alternative conditions. Depending on experimental conditions, decay was either superficial or more or less uniform throughout the block. The uniform pattern was associated with higher weight losses than the superficial pattern. These and other results suggest that, although Soft Rot is most readily apparent as a surface decay of near-saturated wood in service, moisture conditions for optimal development may be no different than for decays caused by basidiomycetes. Key words: wood decay, moisture, Chaetomium globosum.
