Comunicacion presentada en el 6th meeting of the IOBC-WPRS Working Group Multitrophic Interaction... more Comunicacion presentada en el 6th meeting of the IOBC-WPRS Working Group Multitrophic Interactions in Soil, celebrado en Cordoba (Espana) del 4 al 7 de abril de 2011.
Trabajo presentado en el Working Group "Biological Control of Fungal and Bacterial Plant Pat... more Trabajo presentado en el Working Group "Biological Control of Fungal and Bacterial Plant Pathogens", celebrado en Graz (Austria) del 7 al 10 de junio de 2010.
In southern Spain, the most destructive root rot diseases of avocado are caused by Rosellinia nec... more In southern Spain, the most destructive root rot diseases of avocado are caused by Rosellinia necatrix and Phytophthora cinnamomi. The addition of organic amendments or mulches produced some benefits; among them, seem to prevent the disease by their influence in the microbial balance in the soil. In this sense, we are studying the effect of the application of different types of amendments to avocado trees, in order to get insight about their influence on the soil microbial communities and activities. The analysis of cultured microorganisms revealed the importance of specific groups of microorganisms in these soils, like actinomycetes or the genera Pseudomonas. The culture-independent technique DGGE revealed the presence of complex bacterial communities in the different treatment with organic mulches.
This study focused on the microbial profile present in an agricultural soil that becomes suppress... more This study focused on the microbial profile present in an agricultural soil that becomes suppressive after the application of composted almond shells (AS) as organic amendments. For this purpose, we analyzed the functions and composition of the complex communities present in an experimental orchard of 40-year-old avocado trees, many of them historically amended with composted almond shells. The role of microbes in the suppression of Rosellinia necatrix, the causative agent of avocado white root rot, was determined after heat-treatment and complementation experiments with different types of soil. Bacterial and fungal profiles obtained from natural soil samples based on the 16S rRNA gene and ITS sequencing revealed slight differences among the amended (AS) and unamended (CT) soils. When the soil was under the influence of composted almond shells as organic amendments, an increase in Proteobacteria and Ascomycota groups was observed, as well as a reduction in Acidobacteria and Mortiere...
Pseudomonas fluorescens PCL1606 is a rhizobacteria with biocontrol activity against many soil-bor... more Pseudomonas fluorescens PCL1606 is a rhizobacteria with biocontrol activity against many soil-borne phytopathogenic fungi. Its antagonist activity strongly correlates with the production of the antibiotic 2-hexyl, 5-propyl resorcinol (HPR). However, other antibiotics could be detected in P. fluorescens PCL1606, such as pyrrolnitrin (PRN) and hydrogen cyanide (HCN), and could be also related to its antagonist activity. To determine the role of these antibiotics on biocontrol, a collection of mutants in different antibiotics was initiated, studying in first place the genes involved in the production of HPR. A collection of site-directed mutants to the homologous dar operĂłn, related to the HPR production in P. fluorescens PCL1606, have been constructed. Characterization of the potential traits involved in the biocontrol activity of these derivative strains were performed, including antagonism, motility, production of signal molecules, biofilm formation and biocontrol. Our results showe...
Microorganisms in Industry and Environment - From Scientific and Industrial Research to Consumer Products - Proceedings of the III International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2009), 2010
One of the main avocado diseases in southern Spain is white root rot caused by the fungusRosellin... more One of the main avocado diseases in southern Spain is white root rot caused by the fungusRosellinia necatrixPrill. The use of organic soil amendments to enhance the suppressiveness of natural soil is an inviting approach that has successfully controlled other soilborne pathogens. This study tested the suppressive capacity of different organic amendments againstR. necatrixand analyzed their effects on soil microbial communities and enzymatic activities. Two-year-old avocado trees were grown in soil treated with composted organic amendments and then used for inoculation assays. All of the organic treatments reduced disease development in comparison to unamended control soil, especially yard waste (YW) and almond shells (AS). The YW had a strong effect on microbial communities in bulk soil and produced larger population levels and diversity, higher hydrolytic activity and strong changes in the bacterial community composition of bulk soil, suggesting a mechanism of general suppression. ...
ABSTRACT This study tested the effectiveness of single and combined applications of Trichoderma a... more ABSTRACT This study tested the effectiveness of single and combined applications of Trichoderma and rhizobacterial strains to control white root rot (WRR) caused by Rosellinia necatrix in avocado plants. Three Trichoderma, two T. atroviride and one T. virens monoconidal strains and four bacterial strains (Bacillus subtilis, Pseudomonas pseudoalcaligenes and two P. chlororaphis) were assayed to determine their compatibilities in vitro. In addition, the effects of the bacterial filtrates were evaluated against the Trichoderma strains and reciprocally; these filtrates were applied alone or in combination to determine their effectiveness against R. necatrix. Individual control agents or combinations of them were applied to avocado plants that were artificially inoculated with a virulent R. necatrix strain. Compatibility between the combined Trichoderma applications and the bacterial strains was observed and these combinations significantly improved the control of R. necatrix during the in vitro experiments. A relative protective effect of some Trichoderma and bacteria was observed on the control of avocado WRR when they were applied singly. The combinations of T. atroviride strains with bacterial strains P. chlororaphis and P. pseudoalcaligenes showed a better control of avocado WRR, whereas the rest of Trichoderma and bacteria combinations also reduced significantly the level of disease and induced a delay at the onset of disease with respect to avocado plants inoculated either with Trichoderma or bacteria.
Comunicacion presentada en el 6th meeting of the IOBC-WPRS Working Group Multitrophic Interaction... more Comunicacion presentada en el 6th meeting of the IOBC-WPRS Working Group Multitrophic Interactions in Soil, celebrado en Cordoba (Espana) del 4 al 7 de abril de 2011.
Trabajo presentado en el Working Group "Biological Control of Fungal and Bacterial Plant Pat... more Trabajo presentado en el Working Group "Biological Control of Fungal and Bacterial Plant Pathogens", celebrado en Graz (Austria) del 7 al 10 de junio de 2010.
In southern Spain, the most destructive root rot diseases of avocado are caused by Rosellinia nec... more In southern Spain, the most destructive root rot diseases of avocado are caused by Rosellinia necatrix and Phytophthora cinnamomi. The addition of organic amendments or mulches produced some benefits; among them, seem to prevent the disease by their influence in the microbial balance in the soil. In this sense, we are studying the effect of the application of different types of amendments to avocado trees, in order to get insight about their influence on the soil microbial communities and activities. The analysis of cultured microorganisms revealed the importance of specific groups of microorganisms in these soils, like actinomycetes or the genera Pseudomonas. The culture-independent technique DGGE revealed the presence of complex bacterial communities in the different treatment with organic mulches.
This study focused on the microbial profile present in an agricultural soil that becomes suppress... more This study focused on the microbial profile present in an agricultural soil that becomes suppressive after the application of composted almond shells (AS) as organic amendments. For this purpose, we analyzed the functions and composition of the complex communities present in an experimental orchard of 40-year-old avocado trees, many of them historically amended with composted almond shells. The role of microbes in the suppression of Rosellinia necatrix, the causative agent of avocado white root rot, was determined after heat-treatment and complementation experiments with different types of soil. Bacterial and fungal profiles obtained from natural soil samples based on the 16S rRNA gene and ITS sequencing revealed slight differences among the amended (AS) and unamended (CT) soils. When the soil was under the influence of composted almond shells as organic amendments, an increase in Proteobacteria and Ascomycota groups was observed, as well as a reduction in Acidobacteria and Mortiere...
Pseudomonas fluorescens PCL1606 is a rhizobacteria with biocontrol activity against many soil-bor... more Pseudomonas fluorescens PCL1606 is a rhizobacteria with biocontrol activity against many soil-borne phytopathogenic fungi. Its antagonist activity strongly correlates with the production of the antibiotic 2-hexyl, 5-propyl resorcinol (HPR). However, other antibiotics could be detected in P. fluorescens PCL1606, such as pyrrolnitrin (PRN) and hydrogen cyanide (HCN), and could be also related to its antagonist activity. To determine the role of these antibiotics on biocontrol, a collection of mutants in different antibiotics was initiated, studying in first place the genes involved in the production of HPR. A collection of site-directed mutants to the homologous dar operĂłn, related to the HPR production in P. fluorescens PCL1606, have been constructed. Characterization of the potential traits involved in the biocontrol activity of these derivative strains were performed, including antagonism, motility, production of signal molecules, biofilm formation and biocontrol. Our results showe...
Microorganisms in Industry and Environment - From Scientific and Industrial Research to Consumer Products - Proceedings of the III International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2009), 2010
One of the main avocado diseases in southern Spain is white root rot caused by the fungusRosellin... more One of the main avocado diseases in southern Spain is white root rot caused by the fungusRosellinia necatrixPrill. The use of organic soil amendments to enhance the suppressiveness of natural soil is an inviting approach that has successfully controlled other soilborne pathogens. This study tested the suppressive capacity of different organic amendments againstR. necatrixand analyzed their effects on soil microbial communities and enzymatic activities. Two-year-old avocado trees were grown in soil treated with composted organic amendments and then used for inoculation assays. All of the organic treatments reduced disease development in comparison to unamended control soil, especially yard waste (YW) and almond shells (AS). The YW had a strong effect on microbial communities in bulk soil and produced larger population levels and diversity, higher hydrolytic activity and strong changes in the bacterial community composition of bulk soil, suggesting a mechanism of general suppression. ...
ABSTRACT This study tested the effectiveness of single and combined applications of Trichoderma a... more ABSTRACT This study tested the effectiveness of single and combined applications of Trichoderma and rhizobacterial strains to control white root rot (WRR) caused by Rosellinia necatrix in avocado plants. Three Trichoderma, two T. atroviride and one T. virens monoconidal strains and four bacterial strains (Bacillus subtilis, Pseudomonas pseudoalcaligenes and two P. chlororaphis) were assayed to determine their compatibilities in vitro. In addition, the effects of the bacterial filtrates were evaluated against the Trichoderma strains and reciprocally; these filtrates were applied alone or in combination to determine their effectiveness against R. necatrix. Individual control agents or combinations of them were applied to avocado plants that were artificially inoculated with a virulent R. necatrix strain. Compatibility between the combined Trichoderma applications and the bacterial strains was observed and these combinations significantly improved the control of R. necatrix during the in vitro experiments. A relative protective effect of some Trichoderma and bacteria was observed on the control of avocado WRR when they were applied singly. The combinations of T. atroviride strains with bacterial strains P. chlororaphis and P. pseudoalcaligenes showed a better control of avocado WRR, whereas the rest of Trichoderma and bacteria combinations also reduced significantly the level of disease and induced a delay at the onset of disease with respect to avocado plants inoculated either with Trichoderma or bacteria.
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