The rhizobacterium Pseudomonas chlororaphis PCL1606 doesn´t have PGPR activity as additional mechanism to biocontrol

Pseudomonas chlororaphis PCL1606 was isolated from rhizosphere of healthy avocado trees, growing in an area affected by white root rot (caused by Rosellinia necatrix), which is one of the most important diseases for avocado crops. PCL1606 revealed strong antagonist activity against R. necatrix, mainly due to the production of the antifungal compound 2-hexyl, 5-propyl resorcinol (HPR). HPR is crucial for the biocontrol activity, and is involved in bacterial colonisation of the avocado root surface. In this word, we elucidated if PCL1606 also presents plant-growth promoting (PGPR) activity as an additional mechanism involved in biological control. To study such PGPR activity, in vitro assays with tomato seedlings and commercial 6-month-old avocado plants were performed. Additionally, activities related with PGPR activity, such as 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole-3-acetic acid (IAA) production, phosphate solubilization or production of siderophores, were also tested. The obtained results showed that P. chlororaphis strain PCL1606 does not present plant growth promoting activity as an additional trait to its biocontrol ability.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Deciphering the suppressive soil microbiota from an avocado crop

Comunicación en pósterDifferent strategies based on ecological principles have been approached in sustainable agriculture causing positive effects, including the induction of soil suppressiveness against a wide range of soilborne pathogens. Suppressiveness against the phytopathogenic fungus Rosellinia necatrix was observed after the application of composted almond shells in avocado crops. Previous works have analyzed the use of this traditional strategy and applied new microbial community analysis techniques in order to help in the identification of targeted sustainable agricultural strategies. These studies have focused on the microbial profile from an induced-suppressive soil where the soil microbiome had a proven essential role. Microbial profiles based on the 16S rRNA gene and ITS regions sequencing were analysed and an increase in Gammaproteobacteria and Dothideomycetes groups, as well as a reduction in Xylariales (where R. necatrix is allocated) were observed. These results led to the bacterial isolation of different groups of Gammaproteobacteria from this suppressive soil in order to identify new strains with biological control properties. Different characterization tests were performed, and a final selection of representative strains belonging to the genus Pseudomonas and related groups showed, all of them, plant disease protection abilities. Moreover, using previously described biological control agents against R. necatrix, a bacterial synthetic community have been design in order to improve the knowledge of the multitrophic interactions that occur during biological control process.This work was supported by Plan Nacional I+D+I (MINECO, Spain) (AGL2014-52518-C2-IR) and co-financed by FEDER funds (EU). C.Vida was supported by a PhD fellowship from the FPI program of MINECO. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Isolation, characterization and selection of Pseudomonas spp. as biological control agents from a suppressive soil

Bacterial profile from a suppressive soil against Rosellinia necatrix, fungal pathogen of avocado roots, were obtained by 16S rRNA gene sequencing. The results revealed a significant increase in the bacterial class of Gammaproteobacteria, especially in some antagonistic representatives of Pseudomonas spp. For this reason, a collection of 246 bacterial isolates was obtained from this suppressive soil in order to identify new strains with antifungal activity against this fungal phytopathogen. First, we performed an isolation on a selective medium for Pseudomonas-like microorganisms. Then, we used different characterization tests in order to analyse the bacterial collection, including the identification of the general metabolic profile of glucose, the profiling of antifungals produced, both the putative production of antifungal compounds and lytic exoenzymes, as well as the evaluation of traits related with beneficial effects on plants. A final selection of representative strains resulted in antifungal isolates belonging to the genus Pseudomonas and related groups. These selected strains were tested for plant protection by an in vivo experiment using avocado and wheat plants challenged by the pathogen R. necatrix, showing all of them an antifungal ability and plant disease protection.This work was supported by Plan Nacional I+D+I from MINECO (Spain) (AGL2014-52518-C2-IR) and co-financed by FEDER funds (EU). C.Vida was supported by a PhD fellowship from the FPI program of MINECO.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Isolation, characterization and selection of bacterial isolates from a suppressive soil with beneficial traits to plants

Backgrounds This study focused on the characterization and selection of bacterial strains obtained from a suppressive soil displaying antifungal activity against the soilborne phytopathogenic fungi Rosellinia necatrix. Bacterial profile from this suppressive soil were first obtained by 16S rRNA gene sequencing, revealing a significant increase in the bacterial class Gammaproteobacteria, especially in some antagonistic representatives of Pseudomonas spp. Objectives To obtain and characterize a collection of 246 bacterial isolates obtained from this suppressive soil, in order to identify new strains with antifungal activity against fungal phytopathogens. Methods To obtain the bacterial collection, we performed an isolation on a selective medium for Pseudomonas-like microorganisms. Further characterization tests were used in order to analyse the bacterial collection, including identification of the general metabolic profile of glucose, the profiling of antifungals produced, including both the putative production of antifungal compounds and lytic exoenzymes, and the evaluation of traits related with beneficial effects on plants. Conclusions A final selection of representative strains resulted in antifungal isolates belonging to the genus Pseudomonas, but also some representatives of the genera Serratia and Stenotrophomonas. These selected strains were tested for plant protection by an in vivo experiment using avocado and wheat plants challenged by the pathogen R. necatrix, showing all of them an antifungal ability and plant disease protection. Pseudomonas-like strains isolated from suppressive soils constitute an excellent source for novel microbial biocontrol agents against soilborne fungal pathogens. This work was supported by grant AGL2014-52518-C2-1-R. Carmen Vida and Sandra Tienda are supported by a PhD fellowship from the FPI program of the Spanish Government.This work was supported by grant AGL2014-52518-C2-1-R. Carmen Vida and Sandra Tienda are supported by a PhD fellowship from the FPI program of the Spanish Government; Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Señalización de Pseudomonas chlororaphis PCL1606 en la rizosfera durante las interacciones multitróficas

Comunicación oralPseudomonas chlororaphis PCL1606 es una rizobacteria, que muestra capacidad antagonista y actividad de biocontrol frente a diferentes hongos fitopatógenos de suelo, entre ellos Rosellinia necatrix, que produce la enfermedad denominada podredumbre blanca radicular en el aguacate. Entre otros factores, se ha demostrado que PCL1606 produce un compuesto antifúngico (2-hexil, 5-propil resorcinol o HPR), que resulta clave para el antagonismo y la actividad biocontrol contra R. necatrix. En este trabajo se aborda el estudio en detalle de los procesos de interacción que tienen lugar durante el biocontrol de PCL1606 frente a R .necatrix en la raíz de aguacate. Para ello, se realizará una aproximación mediante RNA-seq, y que revelará que RNA mensajeros están presentes en ese determinado momento, permitiendo la identificación de los genes que se expresan durante el proceso de interacción, y la posible función e implicación en el proceso. Para la puesta a punto de un modelo experimental de interacción sobre el que realizar análisis moleculares, se han iniciado los experimentos realizando análisis de RNA-seq sobre placas de medio de cultivo, que revelaron la inducción y represión de distintos genes de PCL1606 en presencia/ausencia de R. necatrix. Genes representativos seleccionados se emplean como controles para estimar, mediante experimentos qRT-PCR, las condiciones experimentales del ensayo sobre raíz de aguacate. Una vez validado el modelo experimental, se iniciará el estudio de las interacciones multitróficas que tienen lugar mediante análisis de RNA-seq a las distintas condiciones de ensayo. El resultado previsto contempla que el análisis de los genes que se induzcan/repriman en este proceso, aportarán información fundamental sobre la biología del agente de biocontrol y los procesos que tienen lugar durante las interacciones multitróficas en el biocontrol.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La rizobacteria Pseudomonas chlororaphis PCL1606, no presenta actividad promotora del crecimiento como mecanismo adicional de biocontrol

Pseudomonas chlororaphis PCL1606 es una rizobacteria, que muestra capacidad antagonista y actividad de biocontrol frente a diferentes hongos fitopatógenos de suelo, entre ellos Rosellinia necatrix, que produce la enfermedad denominada podredumbre blanca radicular en la planta de aguacate. Se ha demostrado que PCL1606 produce el antifúngico 2 hexil, 5 propil resorcinol (HPR), entre otros compuestos antifúngicos. HPR es clave para el antagonismo y la actividad biocontrol contra R. necatrix, así como en la colonización de la rizosfera de aguacate. En este trabajo se analiza la posible actividad PGPR (actividad promotora del crecimiento de la planta mediada por rizobacterias) de P. chlororaphis PCL1606, como mecanismo adicional implicado en el control biológico. Para ello, se realizaron ensayos in vitro con semillas de tomate, así como ensayos en plantas comerciales de aguacate de 6 meses. También se estudiaron actividades relacionadas con el PGPR, como la actividad 1-aminociclopropano-1-carboxylato (ACC) deaminasa, la producción de ácido indol acético (IAA), la solubilización de fosfatos o la producción de sideróforos. Los resultados obtenidos de los distintos ensayos, muestran que la cepa P. chlororaphis PCL1606 no tiene actividad promotora del crecimiento vegetal.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Papel del HPR como molécula señal en las interacciones multitróficas en la bacteria de control biológico pseudomonas chlororaphis PCL1606.

En este trabajo, se analizará a nivel transcriptómico, la expresión/represión de los genes cuando se compara un mutante defectivo en la producción de HPR (mutante en el gen darB) frente a la cepa silvestre, identificando los fenotipos dependientes de la producción de HPR durante el proceso de interacción multitrófica, que se produce durante el control biológico de la podredumbre blanca radicular.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech . Este trabajo se ha financiado gracias a el Plan Nacional de l+D+I del Ministerio de Economía (AGL2014-52518-C2-l-R y AGL2017-83368-C2-l-R; MINECO, España) y cofinanciado con fondos PEDER (EU). S. Tienda está siendo financiada con una ayuda del programa FPI del MINECO

Development of a Pseudomonas-based biocontrol consortium with effective root colonization and extended beneficial side effects for plants under high-temperature stress

The root microbiota plays a crucial role in plant performance. The use of microbial consortia is considered a very useful tool for studying microbial interactions in the rhizosphere of different agricultural crop plants. Thus, a consortium of 3 compatible beneficial rhizospheric Pseudomonas strains previously isolated from the avocado rhizosphere, was constructed. The consortium is composed of two compatible biocontrol P. chlororaphis strains (PCL1601 and PCL1606), and the biocontrol rhizobacterium Pseudomonas alcaligenes AVO110, which are all efficient root colonizers of avocado and tomato plants.Funding for open access charge: Universidad de Málaga / CBU

Fitness Features Involved in the Biocontrol Interaction of Pseudomonas chlororaphis With Host Plants: The Case Study of PcPCL1606

The goal of this mini review is to summarize the relevant contribution of some beneficial traits to the behavior of the species Pseudomonas chlororaphis, and using that information, to give a practical point of view using the model biocontrol strain P. chlororaphis PCL1606 (PcPCL1606). Among the group of plant-beneficial rhizobacteria, P. chlororaphis has emerged as a plant- and soil-related bacterium that is mainly known because of its biological control of phytopathogenic fungi. Many traits have been reported to be crucial during the multitrophic interaction involving the plant, the fungal pathogen and the soil environment. To explore the different biocontrol-related traits, the biocontrol rhizobacterium PcPCL1606 has been used as a model in recent studies. This bacterium is antagonistic to many phytopathogenic fungi and displays effective biocontrol against fungal phytopathogens. Antagonistic and biocontrol activities are directly related to the production of the compound 2-hexyl, 5-propyl resorcinol (HPR), despite the production of other antifungal compounds. Furthermore, PcPCL1606 has displayed additional traits regarding its fitness in soil and plant root environments such as soil survival, efficient plant root colonization, cell-to-cell interaction or promotion of plant growth.This research was supported by the Spanish Plan Nacional I C D C I. Grant AGL2017-83368-C2-1-R and partially supported by the European Union (FEDER). CV and ST were supported by a grant from FPI, Ministerio de Ciencia e Innovación, Spain

Biological control and cross infection of the Neofusicoccum spp. causing mango postharvest rots in Spain.

Mango and avocado are the main subtropical crops in southern Spain. These fruits are grown and processed in the same geographical area and are transported to the rest of Europe. However, postharvest diseases during transportation and storage could damage the export market. These two fruits share, on many occasions, farms, processing and even transport, and could act as cross inoculation source. In this work, symptoms of rot in mango fruits were detected, and analyzed in search of the causal agent. Concurrently, asymptomatic avocado fruits were also analyzed. The main fungal genera found, both in mango and avocado, were Alternaria sp. and Neofusicoccum sp. Of these two genera, only Neofusicoccum sp. was able to reproduce the symptoms of rot in mango like previously detected. Likewise, Neofusicoccum sp. isolates, but not Alternaria sp., could produce rot symptoms in avocado inoculated fruits. Two microbial biological control agents were tested to study the control of this disease through sustainable strategies. These candidates to biological control were Pseudomonas chlororaphis PCL1606. and Bacillus velezensis UMAF6639, both antagonists showed antifungal characteristics. The applications of both microorganisms on the fruit showed significant levels of protection during preventive applications, although only UMAF6639 showed greater persistence in the fruit during the preventive applications in the field. According to our results, it is possible to establish that pathogenic Neofusicoccum parvum and N. mediterraneum are the main causes of mango postharvest rots in southern Spain. These fungi could also be potential pathogens to avocado fruits, suggesting a risk of cross-infections among crops. Biological strategies to control postharvest rots have shown better efficacy of preventive application strategies. Following the same strategy in open field experiments.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech