ABSTRACT: This study addresses the need to understand the presence of functional microorganisms in tropical soils, providing valuable information for conservation and sustainable management. The main objective is to analyze the variability of functional microorganisms at different soil depths and their correlations with physicochemical parameters. To this end, soil samples were collected from 15 random points in a reserved forest and analyzed for physicochemical and microbiological properties at two depths (10 and 20 cm). The following functional microorganisms were quantified: viable aerobes, lactobacilli, actinomycetes, fungi, and nitrogen-fixing bacteria using specific protocols. The non-parametric Wilcoxon test was used to determine differences between depths, and the Pearson correlation coefficient (|ρ| ≥ 0.8) was used to analyze correlations between physicochemical parameters and microorganisms. The results suggest that the abundance of viable aerobic microorganisms, Lactobacillus, Actinomycetes, and Fungi decreases with soil depth, while nitrogen-fixing bacteria show no significant differences. The decrease in abundance is related to factors such as nutrient and oxygen availability and microenvironmental conditions. There is a strong positive correlation between the amount of viable aerobic microorganisms and Lactobacillus with phosphorus content, and a negative correlation between Actinomycetes and clay content. Actinomycetes prefer sandy soils, while Fungi thrive in soils rich in organic matter. The negative correlation between Fungi and Actinomycetes suggests competition for limited resources and possible chemical interactions, such as the production of antibiotic compounds by Actinomycetes. This study demonstrates that a detailed understanding of soil microbiota can offer new opportunities to improve agricultural practices, especially in terms of soil fertility management and environmental sustainability.

RESUMEN: Este estudio aborda la necesidad de entender la presencia microorganismos funcionales en suelos tropicales, proporcionando información valiosa para la conservación y manejo sostenible. Tiene como principal objetivo analizar la variabilidad de microorganismos funcionales en diferentes profundidades del suelo y las correlaciones con los parámetros fisicoquímicos. Para ello se recolectaron muestras de suelo de 15 puntos aleatorios en un bosque reservado y se analizaron propiedades fisicoquímicas y microbiológicas a dos profundidades (10 y 20 cm). Se cuantificaron los siguientes microorganismos funcionales: aerobios viables, lactobacilos, actinomicetos, hongos y bacterias fijadoras de nitrógeno utilizando protocolos específicos. Se empleó la prueba no paramétrica de Wilcoxon para determinar diferencias entre profundidades y el coeficiente de correlación de Pearson (|ρ| ≥ 0,8) para analizar correlaciones entre parámetros fisicoquímicos y microorganismos. Los resultados sugieren que la abundancia de microorganismos aerobios viables, Lactobacillus, Actinomicetos y Fungi disminuye con la profundidad del suelo, mientras que las bacterias fijadoras de nitrógeno no muestran diferencias significativas. La disminución de la abundancia se relaciona con factores como la disponibilidad de nutrientes y oxígeno y las condiciones microambientales. Existe una correlación positiva fuerte entre la cantidad de microorganismos aerobios viables y Lactobacillus con el contenido de fósforo, y una correlación negativa entre Actinomicetos y el contenido de Arcilla. Los Actinomicetos prefieren suelos arenosos, mientras que los Fungi prosperan en suelos ricos en materia orgánica. La correlación negativa entre Fungi y Actinomicetos sugiere competencia por recursos limitados y posibles interacciones químicas, como la producción de compuestos antibióticos por parte de los Actinomicetos. Este estudio demuestra que la comprensión detallada de la microbiota del suelo puede ofrecer nuevas oportunidades para mejorar las prácticas agrícolas, especialmente en términos de gestión de la fertilidad del suelo y sostenibilidad ambiental.

ABSTRACT Growers have adopted monoculture to maintain the high melon (Cucumis melo L.) production demand in the Northeastern region of Brazil. This cultivating practice culminates in up to three crop cycles per year being used in the same growing area. The main objective of this study was to evaluate if the incorporation of plant material used with polyethylene mulch and or in association with commercial soil amendment products can help to condition an environment that is beneficial to soil microbial communities. Two identical greenhouse experiments were conducted using a completely randomized design with seven treatments and seven replications. The treatments were: (C) – Control, (M) - polyethylene mulch, (C+M) - incorporation of Crotalaria juncea L. + polyethylene mulch, (P+M) - incorporation of Pennisetum glaucum L. + polyethylene mulch, (M+CS) - polyethylene mulch + (Compost-Aid® + Soil-Set®, trade names of products produced by Alltech Crop Science), (C+M+CS) - incorporation of C. juncea L. + polyethylene mulch + (Compost-Aid® + Soil-Set®), and (P+M+CS) - incorporation of P. glaucum L. + polyethylene mulch + (Compost-Aid® + Soil-Set®). To quantify the target soil microbiota (fungi, bacteria, sporulating bacteria, and actinomycetes), isolations were attempted on selective culture media specific for each group of microorganisms. The incorporation of P. glaucum together with the use of polyethylene mulch and commercial products (Compost-Aid® and Soil-Set®), (P+M+CS), increased the total fungal population by 183%, total bacteria by 55%, sporulating bacteria by 21%, and actinomycetes by 146% in relation to the control treatment. Cucumis L Brazil area communities replications C (C Control M (M C+M CM (C+M P+M PM P (P+M M+CS MCS CS (M+CS CompostAid® CompostAid Compost Aid® Aid (Compost-Aid SoilSet®, SoilSet Soil Set®, Set Soil-Set® Science, Science , Science) C+M+CS CMCS (C+M+CS Set® Soil-Set®) P+M+CS PMCS (P+M+CS SoilSet®. . fungi, fungi (fungi actinomycetes, actinomycetes) microorganisms P+M+CS, 183 183% 55 55% 21 21% 146 treatment SoilSet® Soil-Set 18 5 2 14 1

RESUMO Os produtores há anos adotam a monocultura para manter a demanda de produção de melão alto (Cucumis melo L.) na região Nordeste do Brasil. Esta estratégia de cultivo é usada em até três ciclos por ano. O objetivo principal deste estudo foi avaliar se a incorporação de material vegetal utilizado com mulch de polietileno e/ou em associação com produtos corretivos de solo pode condicionar um ambiente benéfico para as comunidades microbianas do solo. Dois experimentos idênticos em casa de vegetação foram conduzidos em um delineamento inteiramente casualizado com sete tratamentos e sete repetições. Os tratamentos foram: (C) – Controle, (M) - cobertura de polietileno, (C+M) - incorporação de Crotalaria juncea L. + cobertura de polietileno, (P+M) - incorporação de Pennisetum glaucum L. + cobertura de polietileno, (M+CS) - cobertura de polietileno + (Compost-Aid® + Soil-Set®, nomes comerciais dos produtos produzidos pela Alltech Crop Science), (C+M+CS) - incorporação de C. juncea L. + cobertura de polietileno + (Compost-Aid® + Soil-Set®) e (P+M+CS) - incorporação de P. glaucum L. + cobertura de polietileno + (Compost-Aid® + Soil-Set®). Para quantificar a microbiota do solo (fungos, bactérias, bactérias esporulantes e actinomicetos), foram realizados isolamentos em meios de cultura seletivos para cada grupo de microrganismos. Conclui-se que, coletivamente, a incorporação de P. glaucum juntamente com o uso de mulch de polietileno e os produtos comerciais (Compost-Aid® e Soil-Set®), aumentou a população total de fungos em 183%, bactérias totais em 55%, bactérias esporulantes em 21% e actinomicetos em 146% em relação ao tratamento controle. Cucumis L Brasil ano eou ou repetições C (C Controle M (M C+M CM (C+M P+M PM P (P+M M+CS MCS CS (M+CS CompostAid® CompostAid Compost Aid® Aid (Compost-Aid SoilSet®, SoilSet Soil Set®, Set Soil-Set® Science, Science , Science) C+M+CS CMCS (C+M+CS SoilSet® Set® P+M+CS PMCS (P+M+CS SoilSet®. . fungos, (fungos actinomicetos, actinomicetos) microrganismos Concluise Conclui que coletivamente 183 183% 55 55% 21 146 controle Soil-Set 18 5 2 14 1

Abstract Pantoea ananatis is the causal agent of maize white spot, a foliar disease responsible for significant maize yield reduction worldwide, especially in Brazil. In general, the maize foliar diseases control involves the adoption of resistant genotypes and pesticides application. However, the use of agrochemicals can significantly cause increase production costs, damage to human health and negative environmental impacts. In this sense, the use of biological control agents has been considered among the most promising eco-friendly technologies for sustainable agriculture. Actinobacteria, particularly of Streptomyces genus, has been widely recognized as agroindustrially important microorganism due to its potential in producing diverse range of secondary metabolites, including antibiotics and enzymes. Thus, the aim of this work is to characterize and to evaluate the potential of soil actinobacteria for P. ananatis control. We observed that 59 actinobacteria strains (85%) exhibited proteolytic or chitinolytic activity. Only the strains Streptomyces pseudovenezuelae ACSL 470, that also exhibited high proteolytic activity, S. novaecaesareae ACSL 432 and S. laculatispora ACP 35 demonstrated high or moderate antagonist activity in vitro against P. ananatis. Temporal analysis of metabolites produced by these strains growth in different liquid media indicated greater antibacterial activity at 72 h. In this condition, chromatographic and mass spectrometry analysis revealed that S. pseudovenezuelae ACSL 470 strain produced neomycin, an aminoglycoside antibiotic that displayed high bactericidal activity in vitro against P. ananatis. This is the first report of actinobacteria acting as potential microbial antagonists for P. ananatis control. Further studies are needed to determine the control efficacy of maize white spot disease by Streptomyces strains or their metabolites in greenhouse and field conditions. worldwide Brazil general application However costs impacts sense ecofriendly eco friendly agriculture Actinobacteria genus enzymes Thus P 5 85% 85 (85% S 43 3 7 h condition 47 neomycin conditions 8 (85 4 (8 (

Resumo Pantoea ananatis é o agente causal da mancha branca do milho, doença foliar responsável pela redução significativa da produtividade do milho em todo o mundo, especialmente no Brasil. Em geral, o controle de doenças foliares do milho envolve a adoção de genótipos resistentes e a aplicação de agrotóxicos. No entanto, o uso de agroquímicos pode causar aumento significativo dos custos de produção, danos à saúde humana e impactos ambientais negativos. Nesse sentido, o uso de agentes de controle biológico tem sido considerado uma das tecnologias ecologicamente corretas mais promissoras para a agricultura sustentável. Actinobactérias, particularmente do gênero Streptomyces, têm sido amplamente reconhecidas como microrganismos de importância agroindustrial devido ao seu potencial de produção de diversos metabólitos secundários, incluindo antibióticos e enzimas. Assim, o objetivo deste trabalho é caracterizar e avaliar o potencial de actinobactérias do solo para o controle de P. ananatis. Observamos que 59 cepas de actinobactérias (85%) apresentaram atividade proteolítica ou quitinolítica. Apenas as cepas Streptomyces pseudovenezuelae ACSL 470, que também exibiu alta atividade proteolítica, S. novaecaesareae ACSL 432 e S. laculatispora ACP 35 demonstraram alta ou moderada atividade antagonista in vitro contra P. ananatis. A análise temporal do crescimento dos metabólitos produzidos por essas cepas em diferentes meios líquidos indicou maior atividade antibacteriana em 72 h. Nesta condição, análises cromatográficas e de espectrometria de massa revelaram que a cepa S. pseudovenezuelae ACSL 470 produziu neomicina, um antibiótico aminoglicosídeo que apresentou alta atividade bactericida in vitro contra P. ananatis. Este é o primeiro relato de actinobactérias atuando como potenciais antagonistas microbianos para o controle de P. ananatis. Mais estudos são necessários para determinar a eficácia do controle da doença da mancha branca do milho por cepas de Streptomyces ou seus metabólitos em condições de casa de vegetação e campo. mundo Brasil geral agrotóxicos entanto negativos sentido sustentável Actinobactérias secundários enzimas Assim P 5 85% 85 (85% quitinolítica S 43 3 7 h condição 47 neomicina campo 8 (85 4 (8 (

Resumen: La cepa Streptomyces sp. RL8 fue caracterizada en base a su actividad antagónica frente a hongos fitopatógenos, solubilización de fosfatos, producción de sideróforos, y su efecto en la germinación y crecimiento inicial in vitro de frijol Tépari (Phaseolus acutifolius Gray), bajo condiciones controladas. Se aplicó un diseño experimental completamente al azar con un tratamiento bacteriano basado en RL8 (T) y agua destilada como tratamiento Control (C), con cuatro réplicas por tratamiento y 10 semillas por réplica. Las variables de respuesta estudiadas fueron el porcentaje y tasa de germinación (PG y TG), longitud de tallo y de raíz (LT y LR), biomasa fresca y seca de parte aérea (BFPA y BSPA) y biomasa fresca y seca de raíz (BFR y BSR). RL8 mostró actividad antagónica frente a cuatro fitopatógenos de los cinco evaluados, promovió la producción de sideróforos y la solubilización de fosfatos. A escala experimental se observaron diferencias significativas con respecto al grupo control en PG (65.83 vs 30%), TG (4.16 vs 2.25), LT (3.81 vs 1.65 cm) y LR (5.61 vs 2.13 cm), BFPA (2736.75 vs 18.46.75 mg), BSPA (608.75 vs 361.5 mg), BFR (347.0 vs 115.75 mg) y BSR (101.25 vs 58.25 mg). Estos resultados confirman un efecto positivo de RL8 en la germinación y crecimiento inicial de Phaseolus acutifolius Gray, revelando su potencialidad para ser utilizada en su cultivo orgánico o tradicional. Se sugiere su aplicación a escala piloto y su evaluación como alternativa de producción agroecológica en invernadero y en campo.

Summary: The Streptomyces sp. RL8 strain was characterized based on its antagonistic activity against phytopathogenic fungi, solubilization of phosphates, production of siderophores, and its effect on the germination and initial in vitro growth of Tépari beans (Phaseolus acutifolius Gray), under controlled conditions. A completely randomized experimental design was applied with a bacterial treatment based on RL8 (T) and distilled water as Control treatment (C), with four replicates per treatment and 10 seeds per replicate. The response variables studied were the percentage and germination rate (GP and GR), stem and root length (ST and RL), fresh and dry biomass of aerial part (FBAP and DBAP) and fresh and dry biomass of root (FRB and DRB). RL8 showed antagonistic activity against four phytopathogens of the five evaluated, promoted the production of siderophores and the solubilization of phosphates. On an experimental scale, significant differences were observed with respect to the control group in GP (65.83 vs 30%), GR (4.16 vs 2.25), SL (3.81 vs 1.65 cm) and RL (5.61 vs 2.13 cm), FBAP (2736.75 vs 18.46. 75 mg), DBAP (608.75 vs 361.5 mg), FRB (347.0 vs 115.75 mg) and DRB (101.25 vs 58.25 mg). These results confirm a positive effect of RL8 on the germination and initial growth of Phaseolus acutifolius Gray, revealing its potential to be used in its organic or traditional cultivation. Its application on a pilot scale and its evaluation as an alternative for agroecological production in greenhouse and in the field is suggested.

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.

Resumen Introducción: La resistencia a los antimicrobianos (RAM) es un problema de salud pública que manifiesta la disminuida eficacia de estos agentes en la prevención y tratamiento de una proporción cada vez más amplia de patologías. Los actinomicetos son un grupo bacteriano importante de productores de metabolitos activos contra patógenos. Objetivo: Aislar actinomicetos del bosque tropical de Nariño, con potencial producción de metabolitos inhibitorios contra bacterias multidrogo-resistentes. Materiales y métodos: Se tomaron muestras de suelo de Bosque Tropical Húmedo de la Reserva Natural del Río Ñambí, se analizaron microbiológica y molecularmente. Se estimuló la producción in vitro de metabolitos secundarios y evaluó el efecto inhibitorio de estos extractos contra las bacterias multidrogo-resistentes Escherichia coli y Staphylococcus aureus. Resultados: Se obtuvieron 11 aislados presuntivos, se confirmó que cuatro de ellos correspondieron al género Streptomyces sp. Las pruebas de inhibición contra bacterias multidrogo-resistentes E. coli y S. aureus, permitieron verificar que el aislado P3772 fue el más eficiente en la inhibición de los patógenos. Conclusiones: Todos los actinomicetos evaluados presentan actividad antibacteriana contra al menos una de las bacterias patógenas estudiadas; destacando el aislado P3772, que inhibe a E. coli y S. aureus. Se espera caracterizar los compuestos vinculados a la actividad antibacteriana.

Abstract Introduction: Antimicrobial resistance (AR) is a public health problem that reveals the diminished efficacy of these agents in the prevention and treatment of an increasingly larger number of pathologies. Actinomycetes are an important bacterial producer group of metabolites that are active against pathogens. Objective: To isolate actinomycetes from the tropical forest of Nariño (Colombia), which have the potential to produce inhibitory metabolites against multi-drug resistant bacteria. Materials and methods: Soil samples were taken from the Humid Tropical Forest of the Río Ńambí Natural Reserve and analyzed through microbiological and molecular assays. In vitro production of secondary metabolites was first stimulated, followed by the assessment of the inhibitory effect of these extracts against multi-drug resistant Escherichia coli and Staphylococcus aureus. Results: 11 presumptive isolates were obtained, confirming that four of them corresponded to the Streptomyces sp. genus. The bacterial isolate P3772 was identified as the one with the highest inhibitory effect against multi-drug resistant E. coli and S. aureus. Conclusions: All the actinomycetes evaluated presented antibacterial activity. The isolate P3772 stands out, which inhibited both E. coli and S. aureus. The compounds associated with this antibacterial activity will be characterized in future studies.

Summary: Actinobacteria from the rhizosphere of agricultural crops are a potential source of antagonists against phytopathogenic microorganisms. Thus, the objective of this study was to characterize the antagonistic activity in vitro of actinobacteria from the rhizosphere of avocado trees (Persea americana) against Colletotrichum gloeosporioides and Xanthomonas sp. Actinobacteria were isolated from rhizosphere soil samples of avocado trees var. Hass collected from an orchard from Ziracuaretiro, Michoacán. The isolated strains were assessed against C. gloeosporioides and Xanthomonas sp. by means of in vitro confrontation tests. The antagonistic activity was determined by measuring the radius and diameter of the growth inhibition zone of C. gloeosporioides and Xanthomonas sp., respectively. A total of 41 actinobacterial strains were isolated, of which 44% inhibited growth of at least one of the two plant pathogens. Specifically, 15% of the isolates inhibited growth of C. gloeosporioides, 22% of Xanthomonas sp. and 7% of both phytopathogens. The mycelial growth inhibition radius of C. gloeosporioides fluctuated from 6.6 to 15.5 mm, while in Xanthomonas sp., the inhibition zone was from 15.5 to 62.7 mm. These results indicated the importance of rhizosphere actinobacteria as antagonists of phytopathogenic microorganisms, some of which could be used as potential biological control agents against anthracnose and bacterial leaf spot.

Resumen: Las actinobacterias de la rizosfera de cultivos agrícolas son una fuente potencial de antagonistas contra microorganismos fitopatógenos. El objetivo de este estudio fue caracterizar la actividad antagónica in vitro de actinobacterias de la rizosfera de árboles de aguacate (Persea americana) contra Colletotrichum gloeosporioides y Xanthomonas sp. Las actinobacterias fueron aisladas de muestras de suelo rizosférico de árboles de aguacate var. Hass colectadas de una huerta en el municipio de Ziracuaretiro, Michoacán. Las cepas aisladas fueron evaluadas contra C. gloeosporioides y Xanthomonas sp. mediante ensayos de confrontación in vitro. La actividad antagónica se determinó midiendo el radio y diámetro de la zona de inhibición del crecimiento de C. gloeosporioides y Xanthomonas sp., respectivamente. Se aislaron un total de 41 cepas de actinobacterias, de las cuales el 44% inhibió el crecimiento de al menos uno de los dos fitopatógenos. En específico, el 15% de los aislados inhibió el crecimiento de C. gloeosporioides, el 22% a Xanthomonas sp. y el 7% a ambos fitopatógenos. El radio de inhibición del crecimiento miceliar de C. gloeosporioides fluctuó de entre 6.6 a 15.5 mm, mientras que en Xanthomonas sp. la zona de inhibición fue de entre 15.5 a 62.7 mm. Estos resultados indican la importancia de las actinobacterias de la rizosfera como antagonistas de microorganismos fitopatógenos, algunas de las cuales podrían ser utilizadas como potenciales agentes de control biológico contra la antracnosis y la mancha bacteriana.

Abstract Pepper wilt, caused by Phytophthora capsici, is one of the main threats faced during pepper production. Therefore, this study aimed to evaluate the effect of Streptomyces spp. in the biological control of P. capsici under in vitro and in vivo conditions. The in vitro antagonistic activity of strains ABV38, ABV39 and ABV45 was examined by means of dual confrontation tests. Broth culture supernatant (BCS) from the growth of the strains was irrigated on pepper plants inoculated with P. capsici CH11 (PC CH11) to evaluate wilt suppression. Molecular identification of the strains was carried out by analyzing the partial sequence of the 16S rRNA gene. Under in vitro conditions, strains ABV38, ABV39 and ABV45 inhibited the mycelial growth of PC CH11 by 51, 28 and 50 %, respectively. In the in vivo evaluation, the BCSs of strains ABV38 and ABV45 showed a wilt suppressive effect, with plant survival of 77 and 94 %, respectively. Strain ABV39 did not show a wilt suppressive effect (0 % survival), and nor did the untreated plants. Molecular identification indicated that strains ABV39, ABV38 and ABV45 belong to the genus Streptomyces, of which ABV38 and ABV45 have potential for biorational control of pepper wilt.

Resumen La marchitez del chile, causada por Phytophthora capsici, es una de las principales amenazas durante la producción del cultivo. Por lo anterior, el objetivo de este trabajo fue evaluar el efecto de Streptomyces spp. en el control biológico de P. capsici en condiciones in vitro e in vivo. La actividad antagónica in vitro de las cepas ABV38, ABV39 y ABV45 se realizó mediante ensayos de confrontación dual. El sobrenadante del caldo de cultivo (SNC) del crecimiento de las cepas se irrigó en plantas de chile inoculadas con P. capsici CH11 (PC CH11) para evaluar la supresión de la marchitez. La identificación molecular de las cepas se realizó mediante el análisis de la secuencia parcial del gen ARNr 16S. En condiciones in vitro, las cepas ABV38, ABV39 y ABV45 inhibieron el crecimiento micelial de PC CH11 en 51, 28 y 50 %, respectivamente. En la evaluación in vivo, los SNC de las cepas ABV38 y ABV45 mostraron un efecto supresor de la marchitez, con una supervivencia de las plantas de 77 y 94 %, respectivamente. La cepa ABV39 no mostró un efecto supresor de la marchitez (supervivencia de 0 %), al igual que las plantas no tratadas. La identificación molecular indicó que las cepas ABV39, ABV38 y ABV45 pertenecen al género Streptomyces; de las cuales, ABV38 y ABV45 poseen potencial para el control biorracional de la marchitez del chile.

Summary: The application of agrochemicals to floriculture gradually decreases fertility and populations of beneficial microorganisms of the soil, actinomycetes being biological indicators of edaphic quality. The objective of this study was to compare the changes in population density of actinomycetes in rose, carnation and flower of love floriculture soils, and their treatment with vermicompost. Treatments were flower of love as control, soil with pesticide from rose culture, soil with pesticide from carnation culture, soil with pesticide from rose culture conditioned with vermicompost 40 Mg ha-1 and soil with pesticide from carnation culture conditioned with vermicompost 40 Mg ha-1. During 28 days, total population density of actinomycetes was quantified by count plate. The floriculture soils have a sandy-loam texture, and due to their low content of organic matter, vermicompost was added to the treatments. The total actinomycete population of floriculture soils and vermicompost was 1 × 105 CFU g-1 of soil, which indicated a low content. Changes in the population density of actinomycetes were detected in treatments of soils cultured with rose and carnation with and without vermicompost, being higher in soils cultured with rose and carnation without the addition of vermicompost. The changes in the actinomycete population of soils cultured with rose and carnation indicate that these microorganisms are adapted to the application of pesticides. The addition of vermicompost improved the physicochemical properties of the floricultural soils in their respective treatments.

Resumen: La aplicación de agroquímicos en la floricultura, disminuye gradualmente la fertilidad y poblaciones de microorganismos benéficos del suelo, siendo los actinomicetos indicadores biológicos de la calidad edáfica. En el presente artículo se propuso como objetivo comparar los cambios en la densidad poblacional de actinomicetos en suelos florícolas de rosa, clavel y agapando, y su tratamiento con vermicomposta. Los tratamientos fueron agapando como control, suelo con plaguicida del cultivo de rosa, suelo con plaguicida del cultivo de clavel, suelo con plaguicida del cultivo de rosa adicionado con vermicomposta a 40 Mg ha-1 y suelo con plaguicida del cultivo de clavel adicionado con vermicomposta a 40 Mg ha-1. Durante 28 días, se cuantificó la densidad de población de actinomicetos totales, por el método de conteo en placa. Los suelos florícolas son de textura franco-arenosa, por su bajo contenido en materia orgánica, se adicionó vermicomposta a los tratamientos. La población de actinomicetos totales de los suelos florícolas y vermicomposta fue del orden de 1 × 105 UFC g-1 de suelo, lo que indicó un bajo contenido. Se detectaron cambios en la densidad poblacional de actinomicetos en los tratamientos de suelos florícolas de rosa y clavel con y sin vermicomposta, siendo mayor en los suelos florícolas de rosa y clavel sin la adición de vermicomposta. Los cambios en la población de actinomicetos de los suelos cultivados con rosa y clavel indican que estos microorganismos están adaptados a la aplicación de plaguicidas. La adición de vermicomposta mejoró las propiedades fisicoquímicas de los suelos florícolas en sus respectivos tratamientos.

Abstract The research was carried out in the state of Nuevo León, Mexico, during 2018, with the aim of isolating and identifying strains of soil microorganisms and evaluating their antagonistic capacity in vitro against citrus pathogens Lasiodiplodia theobromae and Fomitopsis meliae. For the isolation of the microorganisms, 17 rhizosphere samplings were carried out in different locations and types of vegetation; the samples were heat treated and spread by extension in the potato dextrose agar culture medium added with 0.3% yeast extract and 0.3% malt extract (PDLMA). The isolates obtained were preliminarily evaluated by observation and growth comparison. Of 70 isolates, 15 presented antagonistic activity, which showed inhibition percentages of 39-91%. The actinomycete strains M4 R and M1-101, and the fungus M104 (Penicillium citrinum) caused 84, 91 and 85% inhibition respectively against L. theobromae and 83, 91 and 91% respectively against F. meliae. Isolation of bacteria was achieved, actinomycetes and fungi from the soil capable of inhibiting the growth of L. theobromae and F. meliae fungi causing regressive citrus death.

Resumen La investigación fue realizada en el estado de Nuevo León, México, durante el año 2018, con el objetivo de aislar e identificar cepas de microorganismos de suelo y evaluar su capacidad antagónica in vitro frente a los patógenos de cítricos Lasiodiplodia theobromae y Fomitopsis meliae. Para el aislamiento de los microorganismos se realizaron 17 muestreos de rizósfera en diferentes localidades y tipos de vegetación; las muestras se trataron con calor y se sembraron por extensión en el medio de cultivo papa dextrosa agar adicionado con 0.3% de extracto levadura y 0.3% de extracto de malta (PDLMA). Los aislamientos obtenidos se evaluaron preliminarmente por observación y confrontación del crecimiento. De 70 cepas aisladas, 15 presentaron actividad antagónica, las cuales mostraron porcentajes de inhibición de 39-91%. Las cepas de los actinomicetos M4 R y M1-101, y el hongo M104 (Penicillium citrinum) causaron inhibición de 84, 91 y 85% respectivamente contra L. theobromae y de 83, 91 y 91% respectivamente contra F. meliae. Se logró el aislamiento de bacterias, actinomicetos y hongos del suelo capaces de inhibir el crecimiento de los hongos L. theobromae y F. meliae causantes de muerte regresiva de los cítricos.

Abstract Plant growth-promoting bacteria (PGPB) are a tool that helps to have clean and sustainable agriculture as well as in the reduction of agrochemicals. 35 Actinomycetes were isolated from soil samples from vine, Ica crops. These 35 strains were characterized by their enzymatic ability to degrade different substrates such as oats, lecithin, starch, casein, tween 81 and carboxymethylcellulose. 18 actinobacteria strains were selected that had the best antagonistic response against Aspergillus sp. after being evaluated by bilayer technique in different culture media such as nutrient agar, plate count agar, potato dextrose agar and a new culture medium called ASMICO. To verify the PGPB capacity, phosphates solubilization, nitrogen fixation, siderophore production and acetic indole acid (AIA) production were qualitatively evaluated. 4 actinomycetes were selected with the best antagonism and with at least one of the PGPB characteristics. They then clashed against the phytopathogen Phytophthora cinnamomi which reduced their growth to 10 mm compared to 49 mm of negative control. Using ANOVA with the Statistica 10 software it was confirmed that the new ASMICO culture medium has the greatest effect and is significantly (p <0.05) different compared to the 3 other media used. It is concluded that actinomycetes isolated from Vine crops soils are a potential source to be used as producers of antifungal metabolites as well as PGPB.

Resumen Las bacterias promotoras de crecimiento en plantas (PGPB) promueven una agricultura limpia y sustentable, así como la reducción de agroquímicos. 35 Actinomicetos fueron aislados de muestras de suelo de cultivos de “vid” Vitis vinifera (Vitaceae), Ica. Estas 35 cepas fueron caracterizadas por su capacidad enzimática para degradar “avena”, lecitina, almidón, caseína, tween-81 y carboximetilcelulosa. Se seleccionaron 18 cepas actinomicetales con la mejor respuesta antagonista contra Aspergillus sp. luego de ser evaluadas en diferentes medios de cultivo tales como agar nutritivo, plate count agar, agar papa dextrosa y un nuevo medio de cultivo denominado ASMICO. Se evaluó la capacidad PGPB cualitativamente mediante la solubilización de fosfatos, fijación de nitrógeno, producción de sideróforos y producción de ácido indol acético (AIA). Se seleccionaron 4 actinomicetos con mejor antagonismo y con al menos una de las características PGPB. Luego se enfrentaron contra el fitopatógeno Phytophthora cinnamomi al cual solo creció 10 mm en comparación a los 49 mm del control negativo. Mediante ANOVA utilizando el software Statistica 10, se confirmó que ASMICO posee el mayor efecto y difiere significativamente (p <0.05) a los 3 otros medios utilizados. Se concluye que los actinomicetos aislados de suelos de cultivos de “vid” son una fuente potencial como productores de metabolitos antifúngicos, así como PGPB.

ABSTRACT The mango crop (Mangifera indica) is susceptible to the attack of plant pathogens including fungi that damage the fruit, which is controlled with synthetic fungicides. An alternative to reverse the ecological damage caused by these chemicals is the biological control with antagonistic microorganisms. The objective of this study was to isolate native actinomycetes in mango orchards of the state of Nayarit, Mexico, with antagonistic activity to Colletotrichum sp. Actinomycetes were isolated from soil samples near the rhizosphere of mango trees of Santiago Ixcuintla, Nayarit. We obtained 112 isolates, presenting 25 isolates in vitro antagonistic activity against Colletotrichum sp. Molecular identification showed the diversity of actinomycete isolates and the antagonistic capacity against Colletotrichum sp., indicates that they have the potential to be evaluated in vitro and in vivo against different mango phytopathogens.

RESUMEN El cultivo de mango (Mangifera indica) es susceptible al ataque de fitopatógenos, entre los que destacan hongos que dañan el fruto, que son controlados con fungicidas sintéticos. Una alternativa para revertir los daños ecológicos causados por estas sustancias químicas es el control biológico con, microorganismos antagonistas. El objetivo del presente estudio fue aislar actinomicetos nativos en huertos de mango del estado de Nayarit, México, con actividad antagónica a Colletotrichum sp. Los actinomicetos se aislaron de muestras de suelo cercano a la rizosfera de árboles de mango del municipio de Santiago Ixcuintla, Nayarit. Se obtuvieron 112 aislados, de los cuales 25 presentaron actividad antagónica in vitro contra el Colletotrichum sp. La identificación molecular mostró diversidad de aislados de actinomicetos y la capacidad antagónica manifestada contra Colletotrichum sp., indica que tienen el potencial para ser evaluados in vitro e in vivo contra diferentes fitopatógenos del mango.

ABSTRACT The lemon (Citrus aurantifolia) crop is susceptible to attack by phytopathogens, which are controlled with chemical molecules. An alternative to reverse the ecological damage caused by these chemicals is biological control. The aim of this study was to select strains of actinomycetes with antagonistic activity to Colletotrichum gloeosporioides. It was determined the antagonistic activity in vitro of 181 strains of actinomycetes, belonging to the Chemical Bioactive Center's strain, against C. gloeosporioides; as well as, the extracellular enzymatic activity of the strains that showed better antagonistic effect. From the total of evaluated strains, 62 showed antagonistic capacity manifested against C. gloeosporioides, indicating that they have the potential to be evaluated in vitro and in vivo against different lemon phytopathogens.

RESUMEN El cultivo de limón (Citrus aurantifolia) es susceptible al ataque de fitopatógenos, que son controlados con moléculas químicas. Una alternativa para revertir los daños ecológicos causados por estas sustancias químicas es el control biológico. El objetivo del presente estudio fue seleccionar cepas de actinomicetos con actividad antagónica a Colletotrichum gloeosporioides. Se determinó la actividad antagónica in vitro de 181 cepas de actinomicetos, pertenecientes al cepario del Centro de Bioactivos Químicos, contra C. gloeosporioides; así como, la actividad enzimática extracelular de las cepas que exhibieron mejor efecto antagonista. Del total de cepas evaluadas, 62 mostraron capacidad antagónica manifestada contra C. gloeosporioides, indica que tienen el potencial para ser evaluadas in vitro e in vivo contra diferentes fitopatógenos del limón.

Cocoa (Theobroma cacao L.) is an important crop for Peru; reports of high cadmium content (Cd2+) cause problems for the sector. However, research highlights that organic management improves the microbiological activity of the soil and the absorption of cadmium in almonds. Therefore, the effect of compost and NPK in different soil microbial groups and the available Cd in soils and cocoa beans CCN-51 was evaluated. A completely randomized block design was used, with four treatments and four repetitions, where: T1 control, T2 compost (3 000 kg. ha-1), T3 NPK (84-35-161) and T4: compost (1 500 kg. ha-1) plus NPK (42-18-80). The population of viable aerobes, actinomycetes, fungi and nitrogen fixers were evaluated using the plate count technique with serial dilutions (10³). The Cd available with 0.05 M EDTA and in almonds by 4: 1 perchloric nitric acid digestion. The population of viable aerobes was 10(4) UFC / g, actinomycetes 10(4) to 10(5), fungi and nitrogen fixers 10³ UFC/g; the Cd in the soil varies from 0.17 to 0.25 µg. g-1 and in almonds from 0.31 to 0.43 µg. g-1 No differences (p <0.05) were found between treatments and the different microbial groups, except Cd2+ in almonds. It is concluded that the compost showed potential to reduce the Cd in cocoa almonds

El cacao (Theobroma Cacao L.) es un cultivo importante para Perú; los reportes de elevados contenidos de cadmio (Cd2+) causan problemas al sector. Sin embargo, las investigaciones destacan que el manejo orgánico mejora la actividad microbiológica del suelo y la absorción del cadmio en almendras. Por ello, se evaluó el efecto del compost y NPK en diferentes grupos microbianos del suelo y el Cd disponible en suelos y granos de cacao CCN-51. Se utilizó un diseño de bloque completamente aleatorizado, con cuatro tratamientos y cuatro repeticiones, donde: T1 testigo, T2 compost (3 000 kg. ha-1), T3 NPK (84-35-161) y T4: compost (1 500 kg. ha-1) más NPK (42-18-80). Se evaluó a través de la técnica de recuento en placa con diluciones seriadas (10³) la población de aerobios viables, actinomicetos, fungi y fijadores de nitrógeno. El Cd disponible con EDTA 0,05 M y en almendras por digestión acida Nítrico perclórico 4:1. La población de aerobias viables fue de 10(4) UFC/g, actinomicetos 10(4) a 10(5), los fungi y fijadores de nitrógeno 10³ UFC/g; el Cd en el suelo varía de 0,17 a 0,25 µg. g-1 y en almendras de 0,31 a 0,43 µg. g-1. No se encontró diferencias (p<0,05) entre tratamientos y los diferentes grupos microbianos, excepto Cd2+ en almendras. Se concluye que el compost mostró potencial para reducir el Cd en almendras de cacao

Potato crops are affected by a great number of pathogens that decrease their quality and productivity. One way of controlling these phytopathogens is through the use of antagonistic microorganisms, especially those isolated from the microbial community located in the rhizosphere. In this study, 49 strains of actinomycetes were isolated and their antagonist capacity against phytopathogens that affect Solanum tuberosum was assessed. 26.5% showed antagonist activity against Pectobacterium carotovorum, 69.4% against Fusarium sp., 44.9% against Lasiodiplodia sp., 55.1% against Rhizoctonia solani and 46.9% against Phytophthora infestans. Cultures of two selected actinomycetes (AND 12 and AND 24) were treated with ethyl acetate, dichloromethane, hexane and butanol, whose crude extracts showed antimicrobial activity, being the most important the extract obtained with ethyl acetate due to its greater spectrum of inhibitory activity. The selected strains were identified by phylogenetic analysis of the 16S rRNA gene as members of the genus Streptomyces. Due to their antagonist capacity demonstrated in the present study, rhizospheric actinomycetes could be considered as potential candidates to be used in pathogen control programs that affect potatoes.

El cultivo de la papa se ve afectado por una gran cantidad de patógenos que disminuyen su calidad y productividad. Uno de los métodos de control de estos fitopatógenos es mediante el uso de microorganismos antagonistas, en especial aquellos que se aíslan de la comunidad microbiana presente en la rizósfera. En este trabajo, se aislaron 49 cepas de actinomicetos y se evaluaron sus capacidades antagonistas frente a fitopatógenos que afectan a Solanum tuberosum. El 26.5% presentó capacidad antagónica frente a Pectobacterium carotovorum, el 69.4% a Fusarium sp., el 44.9% a Lasiodiplodia sp., el 55.1% a Rhizoctonia solani y el 46.9% a Phytophthora infestans. Cultivos de dos actinomicetos seleccionados (AND 12 y AND 24) fueron tratados con acetato de etilo, diclorometano, hexano y butanol, cuyos extractos crudos mostraron actividad antimicrobiana, siendo el extracto obtenido con acetato de etilo el más importante por presentar mayor espectro de actividad inhibitoria. Las cepas seleccionadas se identificaron por análisis filogenético del gen del ARNr 16S como miembros del género Streptomyces. Los actinomicetos rizosféricos, por su probada capacidad antagonista demostrada en el presente estudio, podrían ser considerados como potenciales candidatos a ser utilizados en programas de control de patógenos que afectan a la papa.