ABSTRACT Agriculture requires new alternatives to control pests and diseases; biological controls can be a sustainable alternative for the continued success of this sector. This study was thus carried out to identify yeasts and lactic acid bacteria that have the antagonistic capacity to control three phytopathogens as Botrytis cinerea, Lasiodiplodia theobromae and Alternaria brassicae that have caused significant economic losses in agriculture. Thirteen strains of yeast and seven strains of lactic acid bacteria (LAB) were used to measure the percentage of growth inhibition, production of volatile organic compounds, production of biofilms, and the production of enzymes through a completely randomized design. The yeasts Hanseniaspora opuntiae and Saccharomyces cerevisiae and the LAB Lactococcus lactis and L. brevis stood out for their antagonistic capacity to inhibit the growth of phytopathogens by 66%, 58%, 65% and 39%, respectively. Pest and disease control highly depend on chemical phytosanitary inputs with negative economic, environmental, and social effects. This study demonstrated that the yeast H. opuntiae and the LAB L. brevis have potential as biological controls and has been observed to inhibit growth by more than 39%, providing a sustainable alternative that is less harmful to the environment and human health. To guarantee their effectivity under field conditions, their individual application, consortium application, and concentration, timing, and proper application method must be considered.

Abstract Paenibacillus sonchi genomovar Riograndensis SBR5T is a plant growth-promoting rhizobacterium (PGPR) isolated in the Brazilian state of Rio Grande do Sul from the rhizosphere of Triticum aestivum. It fixes nitrogen, produces siderophores as well as the phytohormone indole-3-acetic acid, solubilizes phosphate and displays antagonist activity against Listeria monocytogenes and Pectobacterium carotovorum. Comprehensive omics analysis and the development of genetic tools are key to characterizing and engineering such non-model microorganisms. Therefore, the complete genome of SBR5T was sequenced, and shown to encode 6,705 proteins, 87 tRNAs, and 27 rRNAs and it enabled a landscape transcriptome analysis that unveiled conserved transcriptional and translational patterns and characterized operon structures and riboswitches. The pangenome of P. sonchi species is open with a stable core pangenome. At the same time, the analysis of genes coding for nitrogenases revealed that the trait of nitrogen fixation is sparse within the Paenibacillaceae family and the presence of Fe-only nitrogenase in the P. sonchi group was exclusive to SBR5T. The development of genetic tools for SBR5T enabled genetic transformation, plasmid construction for constitutive and inducible gene expression, and gene repression using the CRISPRi system. Altogether, the work with P. sonchi can guide the study of non-model bacteria with economic potential. SBRT SBR T growthpromoting growth promoting PGPR (PGPR aestivum indole3acetic indoleacetic indole 3 acetic acid carotovorum nonmodel non model microorganisms Therefore sequenced 6705 6 705 6,70 proteins 8 tRNAs 2 riboswitches P time Feonly Fe only transformation expression system Altogether potential 670 70 6,7 67 7 6,

Resumo O Montado é um ecossistema mediterrânico florestal com particular resiliência, rico em biodiversidade e de grande relevância para a conservação da natureza. No entanto, está exposto a ameaças por pressões ambientais agravadas pelas mudanças climáticas e pela pressão do Homem, o que está a levar ao seu declínio. Os microrganismos do solo são cruciais na manutenção de várias das funções do solo onde se inclui a regulação de azoto no solo disponível para as plantas. As bactérias dos nódulos radiculares das leguminosas (conhecidas por rizóbios) podem melhorar o rendimento destes ecossistemas agroflorestais devido ao processo de fixação biológica de azoto que é levado a cabo pela simbiose que se estabelece entre estas bactérias e as leguminosas. Em Portugal, a mortalidade generalizada registada em sobreiros e azinheiras nas últimas décadas deve-se, entre outros fatores, a infeções por Phytophthora spp. nas raízes destas árvores. É, por isso, importante desenvolverem-se meios de biocontrolo para esta doença. O presente trabalho tem por base a avaliação da dimensão e eficácia da população rizobiana existente em solos de Montado. Foram também avaliadas outras importantes atividades in vitro, das bactérias isoladas dos nódulos radiculares dos trevos, como o antagonismo à Phytophthora, a solubilização de fosfato e a capacidade de degradarem a celulose.

Abstract The Montado is a particularly resilient Mediterranean forest ecosystems, rich in biodiversity and of great importance for nature conservation, However, it is exposed to threats from environmental pressures aggravated by global climate change and human pressure, which is leading to its decline. Soil microorganisms are crucial in the maintenance of several soil functions including the regulation of soil nitrogen available to plants. The bacteria in the root nodules of legumes (known as rhizobia) can improve the performance of these agroforestry ecosystems due to the process of biological nitrogen fixation that is carried out by the symbiosis established between these bacteria and legumes. In Portugal, the widespread mortality recorded in cork and holm oaks in recent decades is due, among other factors, to infections by Phytophthora spp. in the roots of these trees. It is therefore important to develop means of biocontrol for this disease. The present work is based on the evaluation of the size and effectiveness of the rhizobial population existing in Montado soils. It was also evaluated, the in vitro antagonist activity to Phytophthora, of the bacteria isolated from root nodules, phosphate solubilization and the ability to degrade cellulose, an essential component of Phytophthora cell wall.

Abstract Diverse habitats have been screened for novel antimicrobial actinomycetes, while others remain unexplored. In this study, we analyzed the bioactivities of actinomycetes cul-tured from rhizosphere soils of the desert plant Artemisia tridentata and the nearby bulk soils. Actinomycetes were screened for antifungal and antibacterial activities toward a panel of plant pathogens; all comparisons were between activities of rhizosphere soil isolates toward those of its counterpart bulk soil. A selected group of the strongest antifungal isolates were also tested against two antifungal-drug resistant strains of Candida albicans. 16S rDNA partial sequences and phylogenetic analysis of isolates that showed broad-spectrum antifungal activities were performed. Forty-two out of 200 and two soil isolated actinomycetes were selected for their strong antifungal activities. The highest proportion of isolates (p <0.05) from rhizosphere soil of an old plant showed antagonism against gram-positive bacteria (0.483 and 0.224 propor-tions against Bacillus subtilis and Rathayibacter tritici, respectively), and phytopathogenic fungi (0.259, 0.431, and 0.345 proportions against Fusarium oxysporum, Rhizoctonia solani and Pythium ultimum, respectively), while the highest antagonism against the gram-negative bacteria predominated in isolates from the bulk soils. Isolates from a rhizosphere soil of a young plant were characterized for strong antagonist activities against Fusarium oxysporum (0.333 proportion, p<0.05). Phylogenetic analysis of 16S rDNA sequences showed that isolates that exhibited strong antifungal activity were genetically similar. We conclude that the rhizosphere soil of A. tridentata is an excellent source for discovery of actinomycetes with potentially novel antifungal compounds.

Resumen En la búsqueda de actinomicetos antimicrobianos se han estudiado diversos hábitats, pero muchos permanecen aún sin explorar. En este estudio analizamos las actividades biológicas de cultivos de actinomicetos provenientes de suelos rizosféricos de la planta desértica Artemisia tridentata y de suelos no asociados a sus raíces. Los actinomicetos fueron seleccionados por sus actividades antifúngicas y antibacterianas contra un panel de patógenos de plantas. Todas las comparaciones fueron entre las actividades de los aislados rizosféricos y aquellas de los aislados no asociados a las raíces. Un grupo selecto de los aislados con las mayores actividades antifúngicas fueron también evaluados contra 2 cepas de Candida albicans resistentes a antifúngicos. Se realizó la secuenciación parcial del ARNr 16S y el análisis filogenético de los aislados que mostraron actividades antifúngicas de amplio espectro. Se seleccionaron 42 de 202 actinomicetos aislados por sus fuertes actividades antifúngicas. La mayor proporción de aislados de suelo rizosférico de plantas viejas mostraron antagonismo contra bacterias gram positivas y hongos fitopatógenos (proporciones de 0,259; 0,431 y 0,345 contra Fusarium oxyspo-rum, Rhizoctonia solani y Pythium ultimum, respectivamente), mientras que la mayor actividad antagónica contra las bacterias gram negativas predominaron en aislados de suelo no asociado a raíces. Los aislados de suelo rizosférico de plantas jóvenes se caracterizaron por una fuerte actividad antagónica contra F. oxysporum (proporción de 0,333, p < 0,05). El análisis filogenético de secuencias del ADNr 16S mostró que los aislados que presentaron fuerte actividad antifúng-ica fueron genéticamente similares. Concluimos que el suelo rizosférico de A. tridentata es una fuente excelente para el descubrimiento de actinomicetos productores de compuestos antifúngicos potencialmente novedosos.

Abstract Fluorescent Pseudomonas and Bacillus spp. are among the bacteria with the greatest potential for the biological control of plant diseases. The objectives of this research were: i) to identify fluorescent Pseudomonas and Bacillus species from the rhizosphere of wild agaves antagonists of pectinolytic bacteria, and ii) to detect the presence of genes for the biosynthesis of antimicrobial lipopeptides (AMPs) in the antagonist strains. The in vitro antagonist efficiency index (IEA) of 109 strains of fluorescent Pseudomonas and 119 of Bacillus spp. isolated from the rhizosphere of wild agaves against five pectinolytic bacterial strains of the genera Pectobacterium and Dickeya were evaluated. By PCR, antagonistic bacteria were identified by sequencing the 16S rRNA gene and AMPs genes: fenD (fengicin), ituC (iturin), srfAA (surfactin), and bmy (bacillomycin) for Bacillus spp., prnD (pyrrolnitrin), and phlD (2,4-diacetiylphloroglucinol) for fluorescent Pseudomonas were detected with specific primers. The in vitro IEA resulted in the selection of 25 antagonist strains against one or more pectinolytic bacteria. Comparison of the 16S rRNA gene sequences identified 11 (44%) strains in the Bacillus genus and 14 (56%) in Pseudomonas with similarities between 97 and 100%. Among the Bacillus and Pseudomonas species, most harbored between two to four AMPs genes. The ItuC, srfAA, and phlD genes were more frequent in all antagonist strains; all the genes evaluated were detected in the Bacillus subtilis (9B14) and Pseudomonas fluorescens (G3, D4, and H6) strains.

Resumen Pseudomonas fluorescentes y Bacillus spp. se encuentran entre las bacterias con mayor potencial para el control biológico de enfermedades en plantas. Los objetivos de esta investigación fueron: i) identificar especies de Pseudomonas fluorescentes y Bacillus de la rizósfera de agaves silvestres antagonistas de bacterias pectinolíticas, y ii) detectar la presencia de genes para la biosíntesis de lipopéptidos antimicrobianos (AMPs) en las cepas antagonistas. Se evaluó el índice de eficiencia antagonista (IEA) in vitro de 109 cepas de Pseudomonas fluorescentes y 119 de Bacillus spp. aisladas de la rizósfera de agaves silvestre contra cinco cepas bacterianas pectinolíticas de los géneros Pectobacterium y Dickeya. Por PCR, las bacterias antagonistas se identificaron por secuenciación del gen 16S rRNA y se detectaron los genes AMPs: fenD (fengicina), ituC (iturina), srfAA (surfactina), y bmy (bacilomicina) para Bacillus spp.; prnD (pirrolnitrina) y phlD (2,4 diacetilfloroglucinol) para Pseudomonas fluorescentes con iniciadores específicos. Los resultados del IEA in vitro resultó en la selección de 25 cepas antagonistas contra una o más bacterias pectinolítcas. La comparación de las secuencias del gen 16S rRNA identificaron 11 (44%) cepas en el género Bacillus y 14 (56%) en Pseudomonas con similitud entre el 97 y 100%. Entre las especies de Bacillus y Pseudomonas, la mayoría albergó entre dos a cuatro genes AMPs. Los genes ItuC, srfAA y phlD fueron de mayor frecuencia en todas las cepas antagonistas; en las cepas Bacillus subtilis (9B14) y Pseudomonas fluorescens (G3, D4 y H6) se detectaron todos los genes evaluados.

Resumo O fungo micotoxigênico Fusarium verticillioides é o principal patógeno do milho e causa doenças do colmo e da podridão da espiga com perdas econômicas significativas. Além disso, o uso excessivo de fungicidas no controle de F. verticillioides constitui uma ameaça ao meio ambiente e à saúde humana. Assim, alternativas sustentáveis, como o controle biológico, são necessárias para minimizar os riscos associados ao método atual. Este estudo isolou e caracterizou bactérias e fungos que colonizam o estigma do milho para avaliar novos agentes de biocontrole em potencial. As amostras foram coletadas em campos de milho nas localidades brasileiras de Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR e Goiânia-GO. Cento e sessenta e sete microrganismos foram isolados, 46% endofíticos e 54% epifíticos. O teste de antagonismo empregando a técnica de disco de difusão em meio sólido, mostrou que 83% dos isolados apresentaram atividade antagonista contra F. verticillioides. Em seguida, 42 isolados mais eficientes foram identificados a partir do sequenciamento parcial do gene 16S rRNA bacteriano e da região ITS de fungos. Os isolados bacterianos pertencem ao gênero Bacillus (57,1%), Burkholderia (23,8%), Achromobacter (7,1%), Pseudomonas (2,4%) e Serratia (2,4%), enquanto os fungos são Penicillium (2,4%), Candida (2.4), e Aspergillus (2,4%). Os resultados mostraram que microrganismos do estigma do milho podem representar novos agentes promissores para o controle de F. verticillioides.

Abstract The mycotoxigenic fungus Fusarium verticillioides is the primary maize pathogen and causes the maize stalk and ear rot diseases with significant economic losses. Furthermore, the excessive use of fungicides to control F. verticillioides constitutes threats to the environment and human health. Thus, sustainable alternatives such as biological control are needed to minimize the hazards associated with the current method. Although much is known about the vulnerability of the maize silks as a gateway for several fungal pathogens invading the developing grains, studies on the chemical properties of silk extracts and their resident microbiota are scarce. This study isolated and characterized bacteria and fungi that colonize the maize stigma to assess new potential biocontrol agents. The samples were collected from maize fields in the Brazilian localities of Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR, and Goiânia-GO. One hundred sixty-seven microorganisms were isolated, 46% endophytic and 54% epiphytic. First, the antagonist activity was evaluated by the agar disc diffusion method performed in triplicate, and 83% of the isolates showed antagonist activity against F. verticillioides. Then, the 42 most efficient isolates were identified based on the partial sequencing of the bacterial 16S rRNA gene and fungi ITS region. The bacteria belong to the genera Bacillus (57.1%), Burkholderia (23.8%), Achromobacter (7.1%), Pseudomonas (2.4%), and Serratia (2.4%), while the fungi are Penicillium (2.4%), Candida (2.4), and Aspergillus (2.4%). The results showed that microorganisms from maize stigma might represent new promising agents for F. verticillioides control.

Abstract The objective of the present study was to evaluate the antimicrobial potential of Artocarpus heterophyllus dry leaves extracts on S. enterica and E. coli and their interaction with conventional antimicrobials. Dried powdered leaves were used to produce hexane (Hex), methanolic (MeOH) and ethanolic residue (EtOHr) extracts. The antimicrobial test was performed against Escherichia coli, ATCC 25922, E. coli EPEC, CDC 086H35, and Salmonella enterica serotype Enteritidis phagotype 4 (SE PT4) through minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC). The agar diffusion technique, well and disc-variants were used to measure the antimicrobial effect of the plant extract combination with antimicrobial of clinical usage. We highlight the bactericidal effect of jackfruit tree leaves on E. coli and S. enterica SE PT4 at 7.2 mg/mL and the effect of the extracts on antimicrobial activity. The interaction between chloramphenicol and dry leaves extracts was characterized by both synergism and antagonism depending on extract type and bacteria used. The interaction between antimicrobial of clinical usage and jackfruit tree leaves extracts demonstrated changes in susceptibility profile of antimicrobials tending to an antagonist effect. As the jackfruit tree leaves may interfere on antimicrobials action, special attention should be given to its usage as traditional medicine in the treatment of food borne diseases.

Abstract The objective of the present study was to select bacterial strains from the rhizosphere of common bean crop and to determine their potential to control Sclerotium rolfsii under in vitro and in planta conditions. Soil samples were collected in the Municipalities of Ahome, Guasave and Angostura, Sinaloa, México. The strains were evaluated under in vitro conditions, afterwards the best isolates were tested in planta, and were identified based on 16S region of ribosomal DNA (three strains). Sixty-five bacterial isolates were tested against Sclerotium rolfsii with an inhibition from 2.5 to 65%. Acinetobacter pittii (COHUI06), Pseudomonas putida (SANMI02) and Burkholderia sp. (GLS06) inhibited 55, 60 and 65% under in vitro conditions; and resulted not hemolytic and their molecular identification was based on 16S rDNA. Only Burkholderia sp. exherted the highest percentage inhibition in planta to control S. rolfsii with a reduction of incidence and disease severity of 40 and 50% respectively, and promoted the dry weight of the plant. A. pittii and P. putida were not efficient in controlling the fungus in planta. Greenhouse and field studies with these bacteria are suggested.

Resumen El objetivo del presente estudio fue seleccionar cepas bacterianas de la rizósfera del cultivo de frijol y determinar su potencial para el control de Sclerotium rolfsii bajo condiciones in vitro e in planta. Se recolectaron muestras de suelo en los municipios de Ahome, Guasave y Angostura, Sinaloa, México, durante el ciclo agrícola 2018-2019. Los aislados se evaluaron bajo condiciones in vitro y se seleccionaron los mejores para la evaluación in planta e identificación molecular (tres aislados) con base a la región 16S del ADN ribosomal. Se evaluaron 65 aislados bacterianos in vitro contra S. rolfsii con un porcentaje de inhibición de 2.5 a 65%. Acinetobacter pittii (COHUI06), Pseudomonas putida (SANMI02) y Burkholderia sp. (GLS06) inhibieron 55, 60 y 65% bajo condiciones in vitro; además resultaron no hemolíticas. Solo Burkholderia sp. ejerció mayor porcentaje de inhibición in planta para el control de S. rolfsii, con reducción de incidencia y severidad de la enfermedad en un 40 y 50% respectivamente, y promovió el peso seco de la planta. A. pittii o P. putida no fueron eficientes para el control del hongo in planta. Se sugiere hacer estudios con las bacterias en invernadero y campo.

Abstract. The objective was to evaluate the antagonistic effect in vitro of native strains of Trichoderma asperellum, Trichoderma harzianum and two isolates of Bacillus spp. against Fusarium oxysporum and Dickeya chrysanthemi. Bacillus, isolated from soil samples of Aloe vera plantations, was morphologically identified and a modified dual culture confrontation was carried out, placing the F. oxysporum in the center of the Petri dish and Bacillus in the four cardinal points; it was arranged under a completely randomized experimental design with five repetitions, the variables registered were percentage of antagonism, inhibition halo and concentration of conidia. For Trichoderma they were confronted against F. oxysporum and D. chrysanthemi with a dual confrontation, a percentage of inhibition and antagonism classification were determined. In the confrontation of T. asperellum it obtained a percentage of inhibition of 70.5% against F. oxysporum and 41.9% against D. chrysanthemi. Regarding the inhibition halos of Bacillus (B5 and B4), they obtained 4 mm. In the conidia concentration B5 showed 1.3, B4 2.6 and the control 12.6 spores per dilution. Trichoderma and Bacillus represent a viable alternative for the control of F. oxysporum and D. chrysanthemi.

Resumen. El objetivo fue evaluar el efecto antagónico in vitro de cepas nativas de Trichoderma asperellum, Trichoderma harzianum y dos aislados de Bacillus spp. frente a Fusarium oxysporum y Dickeya chrysanthemi. Se identificó morfológicamente a Bacillus, aislado de muestras de suelo de plantaciones de Aloe vera y se realizó una confrontación de cultivos duales modificada, colocando en el centro de la caja Petri F. oxysporum y en los cuatro puntos cardinales las bacterias de Bacillus; para esto se dispuso bajo un diseño experimental completamente al azar con cinco repeticiones, las variables registradas fueron porcentaje de antagonismo, halo de inhibición y concentración de conidios. Para Trichoderma se confrontaron frente a F. oxysporum y D. chrysanthemi con una confrontación dual y se determinó porcentaje de inhibición y clasificación de antagonismo. En la confrontación de T. asperellum obtuvo un porcentaje de inhibición de 70.5 % frente a F. oxysporum y 41.9 % frente a D. chrysanthemi. En cuanto a los halos de inhibición de Bacillus (B5 y B4) obtuvieron 4 mm. En la concentración de conidios B5 mostró 1.3, B4 2.6 y el testigo 12.6 esporas por dilución. Trichoderma y Bacillus representan una alternativa viable para el control de F. oxysporum y D. chrysanthemi.

Abstract The objective of this research was to know the antifungal activity of two endophytic isolates of Bacillus amyloliquefaciens against Fusarium verticillioides under laboratory and greenhouse conditions. In vitro dual cultures inhibition of phytopathogenic fungus was detected in a range of 59 to 62%. The endophytic bacteria reduced F. verticillioides incidence and severity more than 80% in plants that received the treatment compared to the control. The individual application of endophytic bacteria increased the chlorophyll content in leaves more than 150% compared to the control. Chlorophyll levels, stem diameter and fruit weight increased in all plants that received the antagonist strains treatment. The molecular corroboration of bacterial strains indicated 99% of identity withBacillus amyloliquefaciens contained in GenBank database with access codes KU570451.1 and KX665550.1.

Resumen El objetivo de esta investigación fue conocer la actividad antifúngica de dos aislamientos endófitos de Bacillus amyloliquefaciens contra Fusarium verticillioides bajo condiciones de laboratorio e invernadero. La inhibición in vitro en cultivos duales del hongo fitopatógeno se obtuvo en un rango del 59 al 62%. Las bacterias endófitas redujeron la incidencia y la severidad de F. verticillioides más del 80% en las plantas que recibieron el tratamiento con respecto al testigo. La aplicación individual de las bacterias endófitas incrementó el contenido de clorofila en las hojas más del 150% que el testigo. Los niveles de clorofila, el diámetro de tallo y el peso del fruto incrementó en las plantas que recibieron el tratamiento de las cepas antagonistas. La corroboración molecular de las cepas bacterianas indicó el 99% de identidad con Bacillus amyloliquefaciens contenidas en el banco de datos del GenBank con clave de acceso KU570451.1 y KX665550.1.

Abstract The objective of the work focused on characterizing the biodiversity of Phytophthora spp. and rhizobacteria with potential for biocontrol in black pod disease in CCN-51. Nine plant samples with symptoms of the disease were collected from cocoa-producing areas, evaluating their morphological characteristics and identification by PCR. Different morphotypes of colonies are observed: cottony, regular and starry edge characteristic for Phytophthora spp. Electrophoresis profiles reveal an amplicon of 159 bp for P. palmivora, demonstrating its distribution in the nine zones. The tests on mycelial inhibition in vitro to P. palmivora, determined high levels of antagonism of 78 and 60% by direct confrontation with the rhizobacteria. These results in bio-protection to CCN-51 by applications of P. veronii R4, A. calcoaceticus BMR2-12, S. marcescens PM3-8 and P. protegens CHA0 are effective in the control of P. palmivora strain (BL15), without the application of bacteria the disease progress is evidenced at the level foliar at 15 and 19 dpi with (2.00E + 05) zoospores. The edaphic application of rhizobacteria in CCN-51, the promoter capacity to plant growth and suppression of P. palmivora disease.

Resumen El objetivo del trabajo se enfocó en Caracterizar la biodiversidad de Phytophthora spp. y rizobacterias con potencial al biocontrol en la enfermedad de la mazorca negra en CCN-51. Nueve muestras vegetales con síntomas a la enfermedad se recolectaron de áreas productoras de cacao, evaluando sus características morfológicas e identificación por PCR. Se observan distintos morfotipos de colonias; algodonosos, borde regular y estrellado característico para Phytophthora spp. Los perfiles de electroforesis revelan un amplicón de 159 pb para P. palmivora, demostrando su distribución en las nueve zonas. Los ensayos en inhibición micelial in vitro a P. palmivora, determinaron niveles altos de antagonismo de 78 y 60% por enfrentamiento directo con las rizobacterias. Los resultados en bioprotección a CCN-51 por aplicaciones de P. veronii R4, A. calcoaceticus BMR2-12, S. marcescens PM3-8 y P. protegens CHA0 son efectivos al control de P. palmivora cepa (BL15), sin aplicación de bacterias se evidencia el avance de la enfermedad a nivel foliar a 15 y 19 dpi con (2,00E+05) zoospporas. La aplicación edáfica de las rizobacterias en CCN-51, se fusionó la capacidad promotora al crecimiento en plantas y supresión de la enfermedad por P. palmivora.

The objective was to characterize the potential PGPR antagonist in the inhibition of mycelial development, conidia in F. oxysporum and spores in M. roreri. The PCR technique was used for the identification of F. oxysporum and M. roreri. Selecting the bacteria: Acinetobacter calcoaceticus BMR2-12, Klebsiella variicola BO3-4, Enterobacter asburiae BA4-19, Enterobacter asburiae PM3-14, Pseudomonas protegens CHA0, Pseudomonas veronii R4 and Bacillus subtilis ATCC-5540. Antagonistic activities were evaluated: a) Mycelial inhibition in F. oxysporum and M. roreri; b) Reduction in production of conidia and spores for 12 and 15 days’ post-incubation. The PCR confirmed the 670 bp amplification for F. oxysporum. The 750 bp sequencing defined a degree of similarity of 99% to M. roreri, when compared to the NCBI GenBank. The application of B. subtilis is of greater antagonistic activity to inhibition (mycelial and conidia) with (95 and 90%) to F. oxyporum. The activity of BO3-4 in M. roreri totally inhibits mycelial development and spore production 12 and 15 days post - incubation respectively. The selection of these biocontrollers and their application as a consortium will offer an alternative to benefit in the reduction of agrochemicals in the cultivation of tomato and cocoa.

El objetivo se enfocó en caracterizar el potencial antagonista de PGPR en inhibición al desarrollo micelial, conidios en F. oxysporum y esporas en M. roreri. La técnica de PCR se empleó para la identificación de F. oxysporum y M. roreri. Seleccionando las bacterias: Acinetobacter calcoaceticus BMR2-12, Klebsiella variicola BO3-4, Enterobacter asburiae BA4-19, Enterobacter asburiae PM3-14, Pseudomonas protegens CHA0, Pseudomonas veronii R4 y Bacillus subtilis. Se evaluaron actividades antagónicas: a) Inhibición micelial en F. oxysporum y M. roreri; b) Reducción en producción de conidios y esporas por 12 y 15 días post-incubación. La PCR confirmó la amplificación de 670 pb para F. oxysporum. La secuenciación de 750 pb definió un grado de similitud del 99% a M. roreri, al compararse con el GenBank de NCBI. La aplicación de B. subtilis es de mayor actividad antagónica a inhibición (micelial y conidios) con (95 y 90%) a F. oxyporum. La actividad de BO3-4 en M. roreri inhibe totalmente el desarrollo micelial y la producción de esporas 12 y 15 días post-incubación respectivamente. La selección de estos bio-controladores y su aplicación como consorcio ofrecerá una alternativa para beneficiar en la reducción de agroquímicos al cultivo de tomate y cacao.

Abstract Diverse microorganisms are living as endophytes in plant tissues and as epiphytes on plant surfaces in nature. Commercial formulations of bacteria antagonist to plant pathogenic microbes and ice nucleation active bacteria have been utilized as an environmentally safe method to manage plant disease and to prevent frost damage respectively. Bacteria were isolated from the leaf and sheath of sugarcane (CP69-1026 CP57-614, CP48-103, CP73-21, and CP70-1143 cultivars) verities grown in the field in Khuzestan province, Iran. Bacteria were found in both sheaths and leaves of sugarcane plants which they were significantly higher in density in leaves and which most were endophytic. The bacterial strains were 10 groups on the basis of the biochemical characteristic, which their 16S rRNA encoding gene from representatives were amplified and subjected to sequencing. Results of sequences analyze using blast software from the NCBI website and phylogenetic analysis showed that the representative strains belonged to a wide variety of phylogenetic groups. These results indicated that they were closely related to Burkholderia and Ralstonia from β-Proteobacteria, Mesorhizobium, Ochrobactrum, Sphingomonas from α-Proteobacteria, Microbacterium, Curtobacterium and Leifsonia from Actinobacteria and Xanthomonas from γ-Proteobacteria. This is the first report of the presence of endophytic and epiphytic bacteria from sugarcane in Khuzestan, Iran.

ABSTRACT Phymatotrichopsis omnivore affect a great number of fruit species causing great economic losses and the use of agrochemicals to combat them, resulting in adverse environmental effects, so it would be very useful to find alternatives that contribute to reduce the use of these chemicals. There are soil-borne microorganisms with mechanisms of inhibition towards various pathogens, which contribute to the use of biological control methods. The objective of this work was to select and identify bacteria strains capable of inhibiting the growth of P. omnivora. To do this, bacteria were isolated from roots of fruit trees with the presence of the disease to evaluate their antagonistic effect in vitro. A total of 88 bacterial isolates were obtained, of which the antifungal capacity was evaluated by simultaneous confrontation of the fungus and the bacteria in triplicate assays. Cottonseeds were inoculated with strains that showed significant inhibition, using in vitro cultures. The bacterial strains M1, N8 and N15 presented greater biocontrol capacity and, considering the results obtained, they were identified by 16S ribosomal DNA sequencing.

RESUMEN Phymatotrichopsis omnívora afecta a un gran número de especies de frutales ocasionando grandes pérdidas económicas, y el uso de agroquímicos para combatirlos ocasionan efectos negativos para el medioambiente, por lo que sería muy útil encontrar alternativas que contribuyan a disminuir el uso de estos químicos. Existen microorganismos nativos del suelo con mecanismos de inhibición hacia diversos patógenos, lo que contribuye al empleo de métodos de control biológico. El objetivo de este trabajo fue seleccionar e identificar cepas de bacterias con capacidad de inhibir el crecimiento de P. omnivora, para lo cual se aislaron bacterias de raíces de árboles frutales con presencia de la enfermedad, con el fin de evaluar su efecto antagónico in vitro. Se obtuvieron 88 aislamientos bacterianos, de los cuales se evaluó la capacidad antifúngica mediante enfrentamiento simultáneo del hongo y la bacteria en ensayos por triplicado. Se inocularon semillas de algodón con las cepas que presentaron inhibición importante utilizando cultivos in vitro. Las cepas bacterianas M1, N8 y N15 presentaron mayor capacidad biocontroladora y teniendo en cuenta los resultados obtenidos, se identificaron mediante secuenciación del ADN ribosómico 16S.

ABSTRACT Extracts rich in saponins from Quillaja saponaria Mol. and populations of rhizobacteria from the genus Pseudomonas, which produce antimicrobial compounds, have been associated with reduction of the fungus Gaeumannomyces graminis var. tritici, the causal agent of take-all disease, which is responsible for severe loss of wheat (Triticum aestivum L.) crops worldwide. However, there is a limited background on the interaction between these bacteria and natural triterpenoids. The aim of this research was to assess the effect of saponin rich extract on Pseudomonas protegens strains 2,4-diacetylphloroglucinol-producers under in vitro and in plant conditions and determining the synergistic effect to be used together to control G. graminis var. tritici in wheat plants. We determined that 8% and 90% of saponins rich Q. saponaria extracts have a differential effect on P. protegens according to their purity (P ( 0.05). On wheat seedlings, quillaja extract with 90% of saponins did not affect the three antagonistic bacterial strain populations assessed, but affected biofilm formation at saponins concentration of 7360 mg L-1. Pseudomonas protegens strains had a variable antagonist activity in wheat plants, and controlled the fungus when were combined with different concentrations of pure Q. saponaria extract, with the concentration of 1840 ppm reducing the take-all disease in 32.5% with respect to the control inoculated with G. graminis var. tritici (P ( 0.05). However, no synergistic effects when the plant extract was combined with the bacterial strains were observed. These results showed the promising and complexity of combining bacterial and plant extract to develop a biopesticide, which could control this fungal disease.