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Berlin Brandenburg

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  • 1
    In: PLoS ONE, 2014, Vol.9(8)
    Description: Rhizosphere competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing rhizosphere competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the rhizosphere competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the rhizosphere of lettuce. The rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the rhizosphere of lettuce with more than 10 6 colony forming units per g root dry mass two weeks after planting. An effect of the soil type on rhizosphere competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable rhizosphere competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in their conduciveness for bottom rot disease. Compared to effect of the soil type of the rhizosphere bacterial communities, the effects of the pathogen and the inoculants were less pronounced. The soil types had a surprisingly low influence on rhizosphere competence and biocontrol activity while they significantly affected the bottom rot disease severity.
    Keywords: Research Article ; Biology And Life Sciences
    E-ISSN: 1932-6203
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  • 2
    Language: English
    In: PLoS ONE, 01 January 2015, Vol.10(9), p.e0138242
    Description: The hemibiotrophic soil-borne fungus Verticillium dahliae is a major pathogen of a number of economically important crop species. Here, the metabolic response of both tomato and Arabidopsis thaliana to V. dahliae infection was analysed by first using non-targeted GC-MS profiling. The leaf content of both major cell wall components glucuronic acid and xylose was reduced in the presence of the pathogen in tomato but enhanced in A. thaliana. The leaf content of the two tricarboxylic acid cycle intermediates fumaric acid and succinic acid was increased in the leaf of both species, reflecting a likely higher demand for reducing equivalents required for defence responses. A prominent group of affected compounds was amino acids and based on the targeted analysis in the root, it was shown that the level of 12 and four free amino acids was enhanced by the infection in, respectively, tomato and A. thaliana, with leucine and histidine being represented in both host species. The leaf content of six free amino acids was reduced in the leaf tissue of diseased A. thaliana plants, while that of two free amino acids was raised in the tomato plants. This study emphasizes the role of primary plant metabolites in adaptive responses when the fungus has colonized the plant.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: PLoS ONE, August 6, 2014, Vol.9(8)
    Description: Rhizosphere competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing rhizosphere competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the rhizosphere competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the rhizosphere of lettuce. The rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the rhizosphere of lettuce with more than 10.sup.6 colony forming units per g root dry mass two weeks after planting. An effect of the soil type on rhizosphere competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable rhizosphere competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in their conduciveness for bottom rot disease. Compared to effect of the soil type of the rhizosphere bacterial communities, the effects of the pathogen and the inoculants were less pronounced. The soil types had a surprisingly low influence on rhizosphere competence and biocontrol activity while they significantly affected the bottom rot disease severity.
    Keywords: RNA ; Biological Pest Control
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Journal of phytopathology, 2011, Vol.159(1), pp.35-44
    Description: The impact of continuous cropping of lettuce on the disease dynamics of bottom rot and genotypic diversity of the causal pathogen Rhizoctonia solani AG 1-IB was studied over 3 years with two crops per year within a field naturally infested with R. solani the pathogen. This field had not had lettuce cultivated in it for 7 years. The disease incidence (DI) and disease severity (DS) were assessed at each harvest and mapped. Surprisingly, a high DI was already observed in the first crop of year one of this field study. In addition, the pathogen was also found to be evenly distributed. Severely infected plants occurred mainly in patches, and the position varied between crops. A significant increase in DS was already observed in the second year, and both temperature conditions and continuous cropping influenced the DS on average over time. Rhizoctonia isolates were randomly collected from the first crop in 1999 and the sixth crop in 2001. The genotypic diversity within the subgroup of R. solani AG 1-IB was analysed by BOX-PCR genomic fingerprinting and the aggressiveness of isolates by bioassay. The fingerprints revealed a high level of genotypic diversity within the AG 1-IB field population. However, continuous cropping was found not to have an impact on genotypic diversity and aggressiveness. ; Includes references ; p. 35-44.
    Keywords: Cropping Systems;
    ISSN: 0931-1785
    E-ISSN: 14390434
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  • 5
    In: PLoS ONE, 2017, Vol.12(3)
    Description: Soil and rhizosphere bacteria produce an array of secondary metabolites including a wide range of volatile organic compounds (VOCs). These compounds play an important role in the long-distance interactions and communication between (micro)organisms. Furthermore, bacterial VOCs are involved in plant pathogens inhibition and induction of soil fungistasis and suppressivenes. In the present study, we analysed the volatile blend emitted by the rhizospheric isolate Pseudomonas donghuensis P482 and evaluated the volatile effect on the plant pathogenic fungi and bacteria as well as one oomycete. Moreover, we investigated the role of the GacS/GacA system on VOCs production in P . donghuensis P482. The results obtained demonstrated that VOCs emitted by P . donghuensis P482 have strong antifungal and antioomycete, but not antibacterial activity. The production of certain volatiles such as dimethyl sulfide, S-methyl thioacetate, methyl thiocyanate, dimethyl trisulfide, 1-undecan and HCN is depended on the GacS/GacA two-component regulatory system. Apparently, these compounds play an important role in the pathogens suppression as the gacA mutant entirely lost the ability to inhibit via volatiles the growth of tested plant pathogens.
    Keywords: Research Article ; Physical Sciences ; Physical Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Physical Sciences ; Physical Sciences ; Biology And Life Sciences ; Medicine And Health Sciences
    E-ISSN: 1932-6203
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  • 6
    In: PLoS ONE, 2017, Vol.12(9)
    Description: Rhizoctonia solani Kühn infects most plant families and can cause significant agricultural yield losses worldwide; however, plant resistance to this disease is rare and short-lived, and therefore poorly understood, resulting in the use of chemical pesticides for its control. Understanding the functional responses of this pathogen during host infection can help elucidate the molecular mechanisms that are necessary for successful host invasion. Using the pathosystem model soybean- R . solani anastomosis group AG1-IA, we examined the global transcriptional responses of R . solani during early and late infection stages of soybean by applying an RNA-seq approach. Approximately, 148 million clean paired-end reads, representing 93% of R . solani AG1-IA genes, were obtained from the sequenced libraries. Analysis of R . solani AG1-IA transcripts during soybean invasion revealed that most genes were similarly expressed during early and late infection stages, and only 11% and 15% of the expressed genes were differentially expressed during early and late infection stages, respectively. Analyses of the differentially expressed genes (DEGs) revealed shifts in molecular pathways involved in antibiotics biosynthesis, amino acid and carbohydrate metabolism, as well as pathways involved in antioxidant production. Furthermore, several KEGG pathways were unique to each time point, particularly the up-regulation of genes related to toxin degradation (e.g., nicotinate and nicotinamid metabolism) at onset of necrosis, and those linked to synthesis of anti-microbial compounds and pyridoxine (vitamin B6) biosynthesis 24 h.p.o. of necrosis. These results suggest that particular genes or pathways are required for either invasion or disease development. Overall, this study provides the first insights into R . solani AG1-IA transcriptome responses to soybean invasion providing beneficial information for future targeted control methods of this successful pathogen.
    Keywords: Research Article ; Medicine And Health Sciences ; Medicine And Health Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences
    E-ISSN: 1932-6203
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  • 7
    In: PLoS ONE, 2016, Vol.11(5)
    Description: Downy mildew is currently the most serious disease of sweet basil around the world. The oomycete causal agent Peronospora belbahrii requires ≥ 4h free leaf moisture for infection and ≥7.5h of water-saturated atmosphere (relative humidity RH≥95%) at night for sporulation. We show here that continued nocturnal fanning (wind speed of 0.4–1.5 m/s) from 8pm to 8am dramatically suppressed downy mildew development. In three experiments conducted during 2015, percent infected leaves in regular (non-fanned) net-houses reached a mean of 89.9, 94.3 and 96.0% compared to1.2, 1.7 and 0.5% in adjacent fanned net-houses, respectively. Nocturnal fanning reduced the number of hours per night with RH≥95% thus shortened the dew periods below the threshold required for infection or sporulation. In experiments A, B and C, the number of nights with ≥4h of RH≥95% was 28, 10 and 17 in the non-fanned net-houses compared to 5, 0 and 5 in the fanned net-houses, respectively. In the third experiment leaf wetness sensors were installed. Dew formation was strongly suppressed in the fanned net-house as compared to the non-fanned net-house. Healthy potted plants became infected and sporulated a week later if placed one night in the non-fanned house whereas healthy plants placed during that night in the fanned house remained healthy. Infected potted basil plants sporulated heavily after one night of incubation in the non-fanned house whereas almost no sporulation occurred in similar plants incubated that night in the fanned house. The data suggest that nocturnal fanning is highly effective in suppressing downy mildew epidemics in sweet basil. Fanning prevented the within-canopy RH from reaching saturation, reduced dew deposition on the leaves, and hence prevented both infection and sporulation of P . belbahrii .
    Keywords: Research Article ; Biology And Life Sciences ; Biology And Life Sciences ; Earth Sciences ; Earth Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Medicine And Health Sciences
    E-ISSN: 1932-6203
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  • 8
    In: PLoS ONE, 2015, Vol.10(3)
    Description: A pot experiment was performed to study the effectiveness of remediation using different plant species and the enzyme response involved in remediating PAH-contaminated soil. The study indicated that species Echinacea purpurea , Festuca arundinacea Schred, Fire Phoenix (a combined F . arundinacea ), and Medicago sativa L. possess the potential for remediation in PAH-contaminated soils. The study also determined that enzymatic reactions of polyphenol oxidase (except Fire Phoenix), dehydrogenase (except Fire Phoenix), and urease (except Medicago sativa L.) were more prominent over cultivation periods of 60d and 120d than 150d. Urease activity of the tested species exhibited prominently linear negative correlations with alkali-hydrolyzable nitrogen content after the tested plants were cultivated for 150d (R 2 = 0.9592). The experiment also indicated that alkaline phosphatase activity in four of the five tested species ( Echinacea purpurea , Callistephus chinensis , Festuca arundinacea Schred and Fire Phoenix) was inhibited during the cultivation process (at 60d and 120d). At the same time, the study determined that the linear relationship between alkaline phosphatase activity and effective phosphorus content in plant rhizosphere soil exhibited a negative correlation after a growing period of 120d (R 2 = 0.665). Phytoremediation of organic contaminants in the soil was closely related to specific characteristics of particular plant species, and the catalyzed reactions were the result of the action of multiple enzymes in the plant rhizosphere soil.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 9
    Language: English
    In: Plant and Soil, 2012, Vol.361(1), pp.343-357
    Description: Co-inoculation of biocontrol agents with different modes of action is assumed to improve biocontrol activity. The present study aimed to investigate the effects of single or co-inoculation of Trichoderma viride strain GB7 and Serratia plymuthica strain 3Re4-18 on microbial communities in the rhizosphere of lettuce and their ability to suppress Rhizoctonia solani AG1-IB.Growth chamber experiments with two different application modes were performed with single or co-inoculation of GB7 and 3Re4-18 in the presence or absence of R. solani. Biocontrol efficacy and plant growth parameters were assessed. Bacterial and fungal communities were analyzed by 16S rRNA gene and ITS fragments PCR-amplified from total community DNA of rhizosphere samples and analyzed by denaturing gradient gel electrophoresis.Compared to the single application, the co-inoculation of 3Re4-18 and GB7 resulted in an improved biocontrol efficacy. DGGE analysis revealed more pronounced effect on microbial community in co-inoculation treatment. The abundance of 3Re4-18 in the rhizosphere seemed to be increased in the presence of R. solani.The applied cultivation-independent methods provided insights into the complex interaction in response to the pathogen and the antagonists. Co-inoculation resulted in an improved biocontrol efficacy and an increased evenness of the microbial communities.
    Keywords: Biocontrol ; Co-inoculation ; Rhizosphere community ; 16S rRNA gene and ITS-based fingerprints
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 10
    In: PLoS ONE, 2018, Vol.13(2)
    Description: Biotic stress, as a result of plant-pathogen interactions, induces the accumulation of reactive oxygen species in the cells, causing severe oxidative damage to plants and pathogens. To overcome this damage, both the host and pathogen have developed antioxidant systems to quench excess ROS and keep ROS production and scavenging systems under control. Data on ROS-scavenging systems in the necrotrophic plant pathogen Rhizoctonia solani are just emerging. We formerly identified vitamin B6 biosynthetic machinery of R . solani AG3 as a powerful antioxidant exhibiting a high ability to quench ROS, similar to CATALASE ( CAT ) and GLUTATHIONE S-TRANSFERASE ( GST ). Here, we provide evidence on the involvement of R . solani vitamin B6 biosynthetic pathway genes; RsolPDX1 ( KF620111.1 ), RsolPDX2 ( KF620112.1 ), and RsolPLR ( KJ395592.1 ) in vitamin B6 de novo biosynthesis by yeast complementation assays. Since gene expression studies focusing on oxidative stress responses of both the plant and the pathogen following R . solani infection are very limited, this study is the first coexpression analysis of genes encoding vitamin B6, CAT and GST in plant and fungal tissues of three pathosystems during interaction of different AG groups of R . solani with their respective hosts. The findings indicate that distinct expression patterns of fungal and host antioxidant genes were correlated in necrotic tissues and their surrounding areas in each of the three R . solani pathosystems: potato sprout- R . solani AG3; soybean hypocotyl- R . solani AG4 and soybean leaves- R . solani AG1-IA interactions. Levels of ROS increased in all types of potato and soybean tissues, and in fungal hyphae following infection of R . solani AGs as determined by non-fluorescence and fluorescence methods using H 2 DCF-DA and DAB, respectively. Overall, we demonstrate that the co-expression and accumulation of certain plant and pathogen ROS-antioxidant related genes in each pathosystem are highlighted and might be critical during disease development from the plant’s point of view, and in pathogenicity and developing of infection structures from the fungal point of view.
    Keywords: Research Article ; Physical Sciences ; Physical Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Medicine And Health Sciences
    E-ISSN: 1932-6203
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