Resumen Las bacterias benéficas que habitan la rizósfera de las plantas son de gran interés agrícola debido a su capacidad para producir fitohormonas durante la colonización radicular. Estas fitohormonas producen cambios fisiológicos en la planta que favorecen una mayor absorción de nutrientes que provocan un rápido crecimiento vegetativo y una mayor producción. Esta investigación tuvo como objetivo evaluar el efecto de la inoculación de dos de estas bacterias, Azospirillum sp. y Pseudomonas fluorescens en el cultivo de maíz harinoso bajo condiciones de campo típicas de la región alto andina. El experimento se realizó utilizando semilla de maíz harinoso de la variedad INIAP-101 con un diseño de bloques completos al azar y seis repeticiones. Los tratamientos correspondieron a: T1 (Azospirillum sp.), T2 (P. fluorescens), T3 (Azospirillum sp. y P. fluorescens), T4 (testigo con fertilización química convencional) y T5 (testigo absoluto). La aplicación de estas bacterias incrementó de manera significativa (p<0,05) la longitud de raíz, el diámetro de la mazorca y el rendimiento del maíz tierno (elotes o choclos). La inoculación combinada de estas bacterias (T3) obtuvo el mayor rendimiento con 19,70 t ha−1 de choclos, mientras que el testigo químico y el testigo absoluto obtuvieron 17,12 y 13,58 t ha−1 de choclos, respectivamente. El análisis económico de T3 reportó un coste/beneficio de 1,35, lo cual indicó que el sinergismo de estos dos géneros podría ser una estrategia sostenible para mejorar los rendimientos y reducir el uso de fertilizantes químicos en el cultivo de maíz de la región Andina.

Abstract Plant growth-promoting bacteria (PGPB) that inhabit root rhizosphere of plants are of great agricultural importance due to their ability to produce phytohormones during root colonization. These phytohormones produce physiological changes in the plant that favor a greater absorption of nutrients, promote growth and increase production. This study analyzed the effect of inoculation of two of these bacteria, Azospirillum sp. and Pseudomonas fluorescens, under field conditions representative of the Andean Highlands. The experiment was carried out using flour corn seed of the INIAP-101 variety in a randomized complete block design with six repetitions. The treatments corresponded to: T1 (Azospirillum sp.), T2 (P. fluorescens), T3 (Azospirillum sp. and P. fluorescens), T4 (control, conventional chemical fertilization) and T5 (absolute control). The application of these bacteria significantly increased (p<0.05) the root length, the diameter of the cob, and the yield of fresh corn (“elotes” or “choclos”). The combined inoculation of these bacteria (T3) obtained the highest yield, with 19.70 t ha−1 of fresh corn; while the chemical control and the absolute control got 17.12 and 13.58 t ha−1 of fresh corn, respectively. The economic analysis of T3 reported a benefit/cost of 1.35, which indicates that the synergism of these two bacteria could be a sustainable strategy to improve yields and reduce the use of chemical fertilizers for corn production in the Andean region.

Summary: The rhizosphere of the great diversity of plants is a complex ecosystem that houses thousands of rhizobacteria that promote plant growth. In the current investigation, three bacteria were isolated from the root of Suaeda sp., which were evaluated to determine the ef fect of their inoculation on Arabidopsis thaliana at distances of 2 and 5 cm and in divided boxes. In the 2 cm test, we noticed that Endo10(7) and Endo10(5) stimulated the plants more than the control, while the proximity to Ecto10(6) caused them to wilt and die. However, at 5 cm, the bacterium that most promoted the development of Arabidopsis was Ecto10(6). In the divided box test, all three bacteria showed the ability to promote growth. In addition, a shade mesh assay was carried out with the inoculation of the bacteria in Solanum lycopersicum L. (Sahariana) and it was found that the promoting ef fect was also observed in the germination and growth of tomato plants. Tests were conducted to determine its ability to produce IAA, siderophores, and solubilize phosphates. Through molecular techniques it was confirmed: the identity of Ecto10(6), Endo10(7), and Endo10(5) as Aneurinibacillus migulanus, Staphylococcus sp. and Bacillus cereus, respectively. Our results provide the rationale for suggesting that these rhizobacteria may increase the growth and development of Arabidopsis thaliana and Solanum lycopersicum.

Resumen: La rizósfera de la gran diversidad de plantas que existen, es un complejo ecosistema que alberga miles de rizobacterias promotoras de crecimiento vegetal. En la presente investigación se aislaron tres bacterias de la raíz de Suaeda sp., y fueron evaluadas para determinar el efecto de su inoculación en Arabidopsis thaliana a distancias de 2 y 5 cm y en cajas divididas. En el ensayo a 2 cm notamos que Endo10(7) y Endo10(5) estimularon más a las plantas que el control, mientras que la cercanía con Ecto10(6) les causó marchitez y muerte. Sin embargo, a 5 cm, la bacteria que fomentó más el desarrollo de Arabidopsis fue Ecto10(6). En el ensayo en cajas divididas las tres bacterias mostraron capacidad para promover crecimiento. Además, se realizó un ensayo en malla sombra con la inoculación de las bacterias en Solanum lycopersicum L. (Sahariana) y se constató que el efecto promotor también se observó en la germinación y crecimiento de las plantas de tomate. Se realizaron pruebas que establecieron su capacidad para producir AIA, sideróforos y solubilizar fosfatos. A través de técnicas moleculares se confirmó la identidad de Ecto10(6), Endo10(7) y Endo10(5) como Aneurinibacillus migulanus, Staphylococcus sp. y Bacillus cereus, respectivamente. Estos resultados nos dan el fundamento para sugerir que estas rizobacterias pueden incrementar el crecimiento y desarrollo de Arabidopsis thaliana y Solanum lycopersicum.

Summary: Plants play a key role in ecosystems. Like other living organisms, plants have microbiomes that allow them to maintain good health and cope with the different types of stress to which they are subjected. At this point, one of the most complex and rich environments is the microbiome that inhabits plants roots in the rhizosphere. In the rhizosphere, there is a complex network of interactions that have only recently begun to be understood. Within these interactions, the biofilm formation on the root surface is a crucial step in the establishment of microbial communities in plants. However, until recent years, its importance in the complex network of interactions that occur between the plant-microorganism, microorganism-microorganism, and its function for soils has begun to be studied. The latest advances in the knowledge of biofilms formation on the rhizosphere, and their role in the production of different antimicrobial compounds in the soil, like different antibiotics, that could be used to improve food production systems or for the benefit of human health, are discussed in this review.

Resumen: Las plantas juegan un papel fundamental en los ecosistemas. Al igual que otros organismos vivos, las plantas cuentan con microbiomas que les permiten mantener una buena salud y hacer frente a los diferentes tipos de estrés a los que están sometidas. En este punto, uno de los entornos más complejos y ricos es el microbioma que habita en las raíces de las plantas, la rizósfera. En la rizósfera, hay una compleja red de interacciones que solo recientemente han comenzado a entenderse. Dentro de estas interacciones, la formación de biopelículas en la superficie de la raíz es un paso crucial en el establecimiento de comunidades microbianas en las plantas. Sin embargo, hasta hace pocos años, se ha comenzado a estudiar su importancia en la compleja red de interacciones que se dan entre las plantas y los microorganismos, entre microorganismo-microorganismo y su función para los suelos. En esta revisión, se discuten los últimos avances en el conocimiento de la formación de biopelículas en la rizósfera y su papel en la producción de diferentes compuestos antimicrobianos en los suelos, como diferentes antibióticos, que podrían utilizarse para mejorar los sistemas de producción de alimentos o en beneficio de la salud humana.

Abstract Agricultural eco-intensification is based on the optimal management of all components of the agroecosystem. One of the components most sensitive to changes is the soil, where the role of microorganisms present in the rhizosphere is fundamental. That is why this work aims to analyze the potential of using microorganisms as a basis for eco-intensification in agricultural systems. This potential was analyzed with a meta-analysis of 203 publications in the period from 2015 to 2022, whose collection was subjected to a frequency analysis of keywords and thematic axes and a cluster analysis (level 3) of the nodes identified using the Nvivo software. The results indicate that only 5.9% analyzed highlight the importance of soil microbiology in agricultural eco-intensification. It is concluded that agricultural eco-intensification promotes fewer inputs, low production costs, and optimal incomes while conserving the soil, improving water content and quality, restoring soil and habitat health, and reducing the emission of greenhouse gases in the agroecosystem. The strengthening of soil microorganisms as an element of eco-intensification represents a niche to improve agroecosystems’ ecology, productivity, and profitability, taking advantage of and maximizing the ecosystem services they offer. This involves deepening research into these interactions to encourage their adoption by farmers.

Resumen La ecointensificación agrícola se basa en el manejo óptimo de todos los componentes del agroecosistema. Uno de los componentes más sensibles a los cambios es el suelo, donde el rol de los microorganismos presentes en la rizosfera es fundamental. Es por ello que el objetivo de este trabajo es analizar el potencial del uso de microorganismos como base para una ecointensificación en los sistemas agrícolas. Este potencial se analizó con un metaanálisis de 203 publicaciones en el periodo de 2015 al 2022, cuyo acervo fue sometido a un análisis de frecuencias de palabras clave, ejes temáticos y de conglomerados (nivel 3) de los nodos identificados mediante el software Nvivo. Los resultados indican que solo el 5.9% analizado destacan la importancia de la microbiología del suelo en la ecointensificación agrícola. Se concluye que la ecointensificación agrícola promueve menos insumos, bajos costos de producción e ingresos óptimos, a la vez que se conserva el suelo, mejora el contenido y la calidad del agua, restablece la salud del suelo y del hábitat y disminuye la emisión de gases de efecto invernadero en el agroecosistema. El fortalecimiento de los microorganismos del suelo como elemento de ecointensificación, representa un nicho para mejorar la ecología, productividad y rentabilidad de los agroecosistemas, aprovechando y maximizando los servicios ecosistémicos que ofrecen. Esto implica profundizar investigaciones en estas interacciones para alentar su adopción por los agricultores.

Resumen Antecedentes: Oaxaca, un estado sureño de México, pertenece al punto caliente Mesoamericano de biodiversidad. El conocimiento taxonómico y de diversidad de los hongos micorrízico arbusculares (HMA) en el estado de Oaxaca se encuentra disperso y poco accesible. Preguntas: ¿Qué especies de HMA se han identificado en Oaxaca y cuál es su distribución? Especies en estudio: Hongos micorrízico arbusculares. Sitio de estudio: Estado de Oaxaca, México. Métodos: Se elaboró un listado de las especies de HMA con la frecuencia de ocurrencia y los sitios de registro. Se consideraron los estudios realizados hasta 2022. La información estuvo disponible en forma dispersa en publicaciones en medios físicos y electrónicos: tesis, proyectos, reportes técnicos y artículos científicos. Resultados: La lista incluye 78 especies, distribuidas en 23 géneros, 10 familias y cuatro órdenes. La familia más diversa fue Glomeraceae (26 especies), seguida por Gigasporaceae (20) y Acaulosporaceae (15), mientras que los géneros más diversos fueron Acaulospora y Glomus (15 y ocho especies, respectivamente). Las especies más frecuentes fueron Funneliformis geosporus, Acaulospora scrobiculata y A. spinosa. La diversidad más elevada de especies se ha reportado en la rizosfera de Agave angustifolia, A. karwinskii y Zea mays (39, 36, y 34 especies, respectivamente). Una nueva especie de HMA fue recientemente aislada en la rizosfera de un agave microendémico. Conclusiones: Las especies de HMA registradas en Oaxaca confirman la posición de este estado como uno de los más altos en diversidad micorrízico arbuscular en México.

Abstract Background: Oaxaca, a southern State in Mexico, belongs to the Mesoamerican hotspot of biodiversity. The taxonomic and diversity knowledge of arbuscular mycorrhizal fungi (AMF) in Oaxaca State is scattered and accessibility to it is difficult. Questions: Which AMF species have been identified in Oaxaca and which is their distribution? Studied species: Arbuscular mycorrhizal fungi. Study site: State of Oaxaca, Mexico. Methods: We prepared an updated and annotated checklist of the AMF species with frequency of occurrence and the sampling sites where the species had been registered. All studies carried out previously (to date, 2022) were considered. Information on AMF taxa was available in scattered form in different publications in physical and electronic media, theses, projects, technical reports, and scientific papers. Results: The checklist includes 78 species, distributed among 23 genera, 10 families, and four orders. The most diverse families were Glomeraceae (26 species), followed by Gigasporaceae (20) and Acaulosporaceae (15), whereas the most diverse genera were Acaulospora and Glomus (15 and eight species, respectively). The most frequent species were Funneliformis geosporus, Acaulospora scrobiculata, and A. spinosa. The highest species diversity has been reported under the rhizosphere of Agave angustifolia, A. karwinskii, and Zea mays (39, 36, and 34 species, respectively). A new AMF species was recently isolated from the rhizosphere of a microendemic agave. Conclusions: The recorded AMF species of Oaxaca State confirms its position as one of the states with the highest AMF species diversity of Mexico.

SUMMARY: Cancer is the second leading cause of death in the world and colorectal cancer is the only cancer that has shown a sustained increase in mortality in the last decade. In the search for new chemotherapeutic agents against cancer, extremophilic microorganisms have shown to be a potential source to obtain molecules of natural origin and with selective cytotoxic action towards cancer cells. In this work we analyzed the ability of a collection of Antarctic soil bacteria, isolated on Collins Glacier from the rhizosphere of Deschampsia antarctica Desv plant, to secrete molecules capable of inhibiting cell proliferation of a colorectal cancer tumor line. Our results demonstrated that culture supernatants from the Antarctic bacteria K2I17 and MI12 decreased the viability of LoVo cells, a colorectal adenocarcinoma cell line. Phenotypic and genotypic characterization of the Antarctic bacteria showed that they were taxonomically related and nucleotide identity analysis based on the 16S rRNA gene sequence identified the bacterium K2I17 as a species belonging to the genus Bacillus.

RESUMEN: El cáncer es la segunda causa de muerte en el mundo y el cáncer colorrectal es el único que presenta un aumento sostenido de la mortalidad en la última década. En la búsqueda de nuevos agentes quimioterapeúticos contra el cáncer, se ha propuesto a los microorganismos extremófilos como una fuente potencial para obtener moléculas de origen natural y con acción citotóxica selectiva hacia las células cancerígenas. En este trabajo analizamos la capacidad de una colección de bacterias de suelo antártico, aisladas en el glaciar Collins desde rizosfera de la planta de Deschampsia antarctica Desv, de secretar moléculas capaces de inhibir la proliferación celular de una línea tumoral de cáncer colorrectal. Nuestros resultados demostraron que los sobrenadantes de cultivo de las bacterias antárticas K2I17 y MI12 disminuyeron la viabilidad de la línea celular de adenocarcinoma colorrectal LoVo, en un ensayo de reducción metabólica de MTT. La caracterización fenotípica y genotípica de las bacterias antárticas, demostró que estaban relacionadas taxonómicamente y el análisis de la identidad nucleotídica en base a la secuencia del gen ARNr 16S identificó a la bacteria K2I17 como una especie perteneciente al género Bacillus.

Resumo As árvores que ocorrem nas margens das áreas agrícolas podem mitigar os danos dos herbicidas residuais. A atividade microbiana rizosférica associada às árvores é um dos principais indicadores de capacidade corretiva. O objetivo deste trabalho foi avaliar a atividade microbiológica rizosférica em espécies arbóreas submetidas aos herbicidas atrazina e sulfentrazone via rizosfera. O experimento foi estruturado em quatro blocos e esquema fatorial 6 × 3. O primeiro fator consistiu em seis espécies de árvores do Brasil e o segundo em soluções de atrazine, sulfentrazone e água. Quatro aplicações de herbicidas foram realizadas via irrigação. Foram determinados a massa seca total das plantas, colonização micorrízica, número de esporos, respiração basal do solo rizosférico e taxa de sobrevivência de plantas bioindicadoras após fitorremediação. Trichilia hirta apresentou maior biomassa quando tratada com atrazina e sulfentrazone. Os herbicidas diminuíram a atividade microbiana em Triplaris americana e não afetaram os indicadores microbiológicos de Myrsine gardneriana, Schizolobium parahyba e Toona ciliata. Menos plantas bioindicadoras sobreviveram no solo com Triplaris americana e sulfentrazone. Os indicadores microbiológicos foram influenciados de formas distintas entre as espécies pela presença dos herbicidas na rizosfera.

Abstract Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.

RESUMO: Microrganismos na rizosfera desempenham um papel importante no crescimento e saúde das plantas. Em todo o mundo, vários patógenos do solo atacam o Capsicum annuum causando danos significativos e perdas econômicas. Este estudo teve como objetivo determinar se a diversidade e composição das comunidades microbianas no solo da rizosfera de plantas de C. annuum é alterada significativamente pela murcha. Usamos o gene 16S rRNA para bactérias e a região espaçadora transcrita interna para fungos para caracterizar os microbiomas da rizosfera de plantas saudáveis e plantas com murcha. Os filos bacterianos mais abundantes foram Proteobacteria e Gemmatimonadetes, enquanto os filos fúngicos foram Ascomycota e Mucoromycota. A diversidade alfa bacteriana não mostrou diferenças significativas na riqueza e diversidade, mas mostrou uma diferença significativa na uniformidade e dominância das espécies. Táxons raros estavam presentes em condições saudáveis e murchas com abundância relativa < 1%. Em fungos, todos os estimadores avaliados apresentaram redução significativa na condição de murcha. A diversidade beta apresentou diferenças significativas na estrutura das comunidades bacterianas e fúngicas, que foram segregadas de acordo com as condições fitossanitárias. O mesmo aconteceu ao comparar a diversidade alfa e beta deste estudo baseado na agricultura orgânica com a de outros estudos baseados na agricultura convencional. Uma diferença significativa foi observada com os estimadores analisados segregando as comunidades da rizosfera dependendo do método de cultivo utilizado. Por fim, a análise de abundância diferencial não apresentou resultados significativos nas comunidades bacterianas; entretanto, nas comunidades fúngicas, os gêneros Fusarium, Thanatephorus, Rhizopus, Curvularia, Cladosporium e Alternaria foram mais abundantes na rizosfera de plantas murchas do que saudáveis. Várias espécies desses gêneros foram previamente relatadas como fitopatógenos de várias plantas, incluindo C. annuum.

ABSTRACT: Rhizosphere microorganisms play an important role in the growth and health of plants. Around the world, diverse soil-borne pathogens attack Capsicum annuum causing significant damage and economic losses. This study determined whether the diversity and composition of microbial communities in the rhizosphere soil of C. annuum plants is significantly changed by wilt disease. We used the 16S rRNA gene for bacteria and the internal transcribed spacer region for fungi to characterize the rhizosphere microbiomes of healthy and wilted plants. The most abundant bacterial phyla were Proteobacteria and Gemmatimonadetes, while the most abundant fungal phyla were Ascomycota and Mucoromycota. The bacterial α-diversity did not show significant differences in richness and diversity, but did show a significant difference in evenness and dominance of species. Rare taxa were present in both healthy and wilted conditions with relative abundances < 1%. In the fungi, all evaluated estimators showed a significant reduction in the wilted condition. The β-diversity showed significant differences in the structure of bacterial and fungal communities, which were segregated according to plant health conditions. The same occurred when comparing the alpha and beta diversity of this study based on organic agriculture with that of other studies based on conventional agriculture. We observed a significant difference with estimators analyzed by segregating rhizosphere communities depending on the farming method used. Finally, the differential abundance analysis did not show significant results in the bacterial communities; however, in the fungal communities, Fusarium, Thanatephorus, Rhizopus, Curvularia, Cladosporium, and Alternaria were more abundant in the rhizosphere of wilted than healthy plants. Species from these genera have been previously reported as phytopathogens of several plants, including C. annuum.

Resumen Los agroecosistemas, como los cultivos de Carya illinoinensis (nogal pecanero), representan una actividad económica importante y de constante crecimiento en La Comarca Lagunera, México. La mayor parte de los macromicetos que se asocian con el nogal pecanero se distribuyen en los primeros horizontes del suelo y la rizosfera de las plantas. Para recolectar los macromicetos asociados al nogal se realizaron recorridos 2 veces por semana, de mayo a octubre de 2018, cubriendo en total 25 ha de una huerta en La Comarca Lagunera, México. A los hongos recolectados se les secuenció la región ITS del ADN ribosomal para corroborar su identificación taxonómica por medio de análisis filogenéticos de máxima verosimilitud y bayesianos. Se encontraron 5 taxones asociados al nogal pecanero, 4 identificados a nivel de especie (Agaricus deserticola, Candolleomyces luteopallidus, Tuber caryophilum y Scleroderma cepa s.l.) y una especie potencialmente nueva (Candolleomyces sp.). De éstos, C. luteopallidus se registra por primera vez en México. Se discute la importancia de la diversidad de los hongos en este sistema agroforestal ya que los hongos saprobios descomponen la materia orgánica y los ectomicorrízicos transfieren macro y micronutrientes esenciales para el crecimiento y productividad del nogal.

Abstract Agroecosystems, such as Carya illinoinensis (pecan tree) orchards, represent an important and constantly growing economic activity in La Comarca Lagunera, Mexico. Most of the macromycetes associated with pecan tree are distributed in the first soil horizons and the plants rhizosphere. To collect the macromycetes associated with pecan trees, we conducted twice a week surveys from May to October 2018 covering 25 hectares of an orchard in La Comarca Lagunera, Mexico. To corroborate their taxonomic identification, we sequenced the DNA ITS region and performed Maximum Likelihood and Bayesian phylogenetic analyses. We found 5 species of macromycetes associated with pecan trees, 4 identified to species level (Agaricus deserticola, Candolleomyces luteopallidus, Tuber caryophylum, and Scleroderma cepa s.l.) and one potential new species (Candolleomyces sp.). Of these, C. luteopallidus is recorded for the first time in Mexico. The importance of fungal diversity in this agroforestry system is discussed because saprobe fungi decompose organic matter and ectomycorrhizal fungi transfer macro and micronutrients essential for pecan trees growth and productivity.

Resumen. Corynespora cassiicola es un patógeno que causa lesiones en diferentes órganos en el cultivo de jitomate. Para su control se utiliza fungicidas sintéticos que requieren más de una aplicación. Trichoderma spp. es un hongo saprófito, altamente interactivo en la rizosfera conocido por sus modos de acción como agente de control biológico contra enfermedades en plantas y promotor del crecimiento vegetal. Se evaluó el efecto en las variables fisiológicas y de crecimiento en plantas de Solanum lycopersicum inoculadas con las concentraciones de esporas 1x100, 1x105, 1x106, 1x107 y 1x108 de Trichoderma asperellum Ta-13-17 y Fithan® (como testigo comercial) como agente de biocontrol de C. cassiicola en condiciones protegidas. Los tratamientos 1x106, 1x108 y Fithan® obtuvieron las tasas fotosintéticas más altas con 20.7, 20.6 y 19.6 µmol m-2 s-1 respectivamente. El tratamiento 1x108 conidios mL-1 obtuvo las medias más altas en las variables de fotosíntesis 20.6 µmol m-2 s-1, rendimiento 1347.02 g por planta y presentaron menor porcentaje de severidad final, menor velocidad en la distribución de la enfermedad y menor acumulación de área bajo la curva del progreso de la enfermedad.

Abstract. Corynespora cassiicola is a pathogen that causes lesions in different organs of tomato crops. For its control, synthetic fungicides are used that require more than one application. Trichoderma spp. is a highly interactive saprophytic fungus in the rhizosphere known as a biological control agent against plant diseases and promoter of plant growth due to its different modes of action. The effect on physiological and growth variables in Solanum lycopersicum plants inoculated with spore concentrations 1x100, 1x105, 1x106, 1x107 and 1x108 of Trichoderma asperellum Ta-13-17 and Fithan®, (as a commercial control) was evaluated. As a biocontrol agent for C. cassiicola under protected conditions. The 1x106, 1x108 and Fithan® treatments obtained the highest photosynthetic rates with 20.7, 20.6 and 19.6 µmol m-2 s-1 respectively. The 1x108 conidia mL-1 treatment obtained the highest means in the photosynthesis variables 20.6 µmol m-2 s-1, yield 1347.02 g per plant and presented a lower percentage of final severity, lower speed in the distribution of the disease and lower accumulation of area under the disease progress curve.

Abstract Coffea sp. is cultivated in many tropical countries. Brazil has always adopted intensive agricultural practices, but organic coffee farming is an alternative system based on the non-use of agrochemicals and the rational management of soils. Metabarcoding 16S analysis using next-generation sequencing has been developed to identify and compare the diversity of the Coffea arabica L. rhizospheric bacterial community in two farming areas in São Paulo, Brazil. Dourado uses conventional farming, while Ribeirão Corrente uses organic. We found broad taxonomic composition, with sequences from 24 phyla, 55 classes, 61 orders, 146 families, and 337genus. The three most abundant phyla were Proteobacteria (38.27%), Actinobacteria (15.56%), and Acidobacteria (16.10%). In organic farming, the top 3 were the family Sphingomonadaceae, order Rhizobiales, genus Nocardioides, and Gp6. The genus Gp2 and the phylum Candidatus Saccharibacteria were the most abundant OTUs exclusively present in conventional farming. In the organic farming practice, Proteobacteria, Actinobacteria, and Acidobacteria were also present among the exclusive OTUs; we also found OTUs belonging to Bacteroidetes, Firmicutes, and Verrucomicrobia. Our study indicates a positive effect of organic farming on microbial communities. Fertilization may directly affect soil microbiota, suggesting that a large and active microbial community low in functional diversity might not adapt to new climatic conditions. A diverse community could provide better resilience to environmental changes, improving the productivity of this important crop.

Resumo Coffea sp. é cultivada em muitos países tropicais. O Brasil sempre adotou práticas agrícolas intensivas, mas a cafeicultura orgânica é um sistema alternativo baseado na não utilização de agrotóxicos e no manejo racional dos solos. A análise Metabarcode 16S utilizando o sequenciamento de última geração foi desenvolvida para identificar e comparar a diversidade da comunidade bacteriana rizosférica de Coffea arabica L. em duas áreas de cultivo em São Paulo, Brasil. Dourado usa agricultura convencional, enquanto Ribeirão Corrente usa agricultura orgânica. Encontramos ampla composição taxonômica, com sequências de 24 filos, 55 classes, 61 ordens, 146 famílias e 337 gêneros. Os três filos mais abundantes foram Proteobacteria (38,27%), Actinobacteria (15,56%) e Acidobacteria (16,10%). Na agricultura orgânica, os 3 primeiros foram a família Sphingomonadaceae, ordem Rhizobiales, gênero Nocardioides e Gp6. O gênero Gp2 e o filo Candidatus Saccaribacteria foram as OTUs mais abundantes exclusivamente presentes na agricultura convencional. Na prática da agricultura orgânica, Proteobacteria, Actinobacteria e Acidobacteria também estiveram presentes entre as OTUs exclusivas; também encontramos OTUs pertencentes a Bacteroidetes, Firmicutes e Verrucomicrobia. Nosso estudo indica um efeito positivo da agricultura orgânica nas comunidades microbianas. A fertilização pode afetar diretamente a microbiota do solo, sugerindo que uma grande e ativa comunidade microbiana com baixa diversidade funcional pode não se adaptar às novas condições climáticas. Uma comunidade microbiana diversificada poderia proporcionar maior resiliência às mudanças ambientais, melhorando a produtividade desta importante cultura agrícola.

Abstract A great diversity of microorganisms in the soil plays an important role in the sustainability of agricultural production systems. Among these microorganisms are bacteria that have the ability to fix atmospheric nitrogen or mineralize phosphorus, thus making it easily assimilable for plants. Maize is the main crop in the highlands of Ecuador (above 2000 meters) and it is predominantly traditional, using native seeds and very little or no agrochemicals. The National Institute of Agricultural Research (INIAP) has a collection of bacteria collected from the rhizosphere of maize in the highlands of Ecuador that has not been taxonomically identified. This research aimed to carry out a biochemical and genetic characterization to establish the identity of the collected nitrogen-fixing and phosphorus-solubilizing bacteria and to understand better the diversity of microorganisms present in the root biome of Andean maize. The hypothesis consisted of determining if there is a difference in the bacteria associated with the rhizosphere of maize in the Andean region of Ecuador compared with other regions. The bacteria underwent classical biochemical characterization based on catalase, oxidase, urease, sulfates, indole, sulfate-indole motility (SIM), and lactose, among others, and genetic identification by 16S rDNA ribosomal gene sequencing, PCR, and SANGER sequencing. A great diversity of microorganisms associated with the rhizosphere of the crop was found, including the genera Agrobacterium, Bacillus, Stenotrophomonas, Acinetobacter, Brevundimonas, Pseudomonas, and Pseudoxanthomonas. INIAP conserves these bacteria in a bank of microorganisms associated with crops of economic importance. They are useful for the development of biofertilizers that could contribute to a more sustainable agriculture in the region.

Resumo Existe uma grande diversidade de microrganismos no solo que desempenham um papel importante na sustentabilidade dos sistemas de produção agrícola. Um grupo deles pertence a bactérias que fixam o nitrogênio atmosférico ou mineralizam o fósforo tornando-o assimilável pelas plantas. O milho é a principal cultura por extensão nas terras altas do Equador (altitude superior a 2.000 m acima do nível do mar) e quase todo o seu cultivo é feito de forma tradicional, com sementes nativas e com muito pouco ou nenhum uso de agroquímicos. O Instituto Nacional de Pesquisa Agropecuária (INIAP) possui uma coleção de bactérias coletadas da rizosfera do milho nas terras altas do Equador que não possuem uma identificação taxonômica conclusiva. O objetivo desta pesquisa foi realizar uma caracterização bioquímica e genética para identificar a identidade das bactérias fixadoras de nitrogênio e solubilizadoras de fósforo coletadas, a fim de conhecer e entender melhor a diversidade de microrganismos presentes no bioma raiz do milho andino. A hipótese consistia em determinar se existe diferença nas bactérias associadas à rizosfera do milho na região andina do Equador, em comparação com outras regiões. As bactérias passaram por uma caracterização bioquímica clássica baseada em catalase, oxidase, urease, sulfatos, indol, motilidade indol sulfato (SIM), lactose, entre outros, e identificação genética através do sequenciamento do gene ribossomal 16S rDNA, por PCR e sequenciamento SANGER. Uma grande diversidade de microrganismos associados à rizosfera da cultura foi encontrada, incluindo os gêneros Agrobacterium, Bacillus, Stenotrophomonas, Acinetobacter, Brevundimonas, Pseudomonas e Pseudoxanthomonas. Estas bactérias são conservadas pelo INIAP num banco de microrganismos associados a culturas de importância económica, sendo úteis para o desenvolvimento de biofertilizantes que possam contribuir para uma agricultura mais sustentável na região.

The extraradical hyphae of arbuscular mycorrhizal fungi (AMF) of one plant root system forage for the soil nutrients and induce the root colonization of the nearby plants, which leads to the formation of common mycorrhizal networks (CMNs) that interconnect roots. Inoculation with AMF can increase the root length, surface area and volume of seedlings in nutrient-limited karstic soils. Mycorrhizal symbioses can secrete glomalin to help promoting soil aggregates for water and nutrients storage, through an extended hyphae to absorb water and nutrients from long distances. AMF can boost rhizosphere soil enzyme activities, and may help to drive carbon sequestration. AMF also improve plant growth by advancing soil quality through influencing its structure and texture. As a result, AMF and CMNs benefit plants through improving soil quality and enhancing morphological (e.g., hyphal length, tillering, number of stolons per individual), physiological (e.g., water use efficiency) and productive (e.g., fresh and dry shoot and root weights) traits.

Las hifas extraradicales de los hongos micorrÃzicos arbusculares (HMA) de un sis- tema radical vegetal se proveen de nutrientes del suelo e inducen la colonización de las raÃces de las plantas cercanas. Esto conduce a la formación de redes micorrÃzicas comunes (RMCs) que interconectan los sistemas radicales. La inoculación con los HMA puede incrementar la longitud radical, el área superficial y el volumen de las plántulas en suelos kársticos limitados en nutrientes. La simbiosis micorrÃzica es capaz de secretar glomalina que incrementa el almacenaje de agua y nutrientes en los agregados del suelo, a través de una extensión de las hifas que permite absorber agua y nutrientes desde largas distancias. Los HMA pueden enriquecer la actividad de las enzimas que están en la rizosfera del suelo, y pueden ayudar a incrementar el secuestro de carbono. Los HMA también benefician el crecimiento de las plantas mejorando la estructura y textura del suelo. Como resultado, los HMA y las RMCs benefician a las plantas modificando el suelo y mejorando caracteres morfológicos (ej., longitud de hifas, macollaje, número de estolones por individuo), fisiológicos (ej. eficiencia de uso del agua) y productivos (ej. pesos frescos y secos del tallo y de las raÃces).

ABSTRACT The Meloidogyne incognita and M. javanica complex cause damage to the coffee plants’ roots with loss of productive potential. Traditional management against this complex is based on the use of chemical molecules which causes problems in soil health and harmful to the environment. In this regard, the Micosplag® biotechnological input [Paecilomyces lilacinus (Thom) Samson, 1974, Metarhizium anisopliae (Metsch) Sorokin and Beauveria bassiana (Balsamo) Vuillemin] and Tricho-D® (Trichoderma harzianum Rifai, 1969) were evaluated under greenhouse conditions against root-knot nematode complex. A dose of 2g. L-1 of water was used for Micosplag® and 10g. L-1 of water for Tricho-D®, applying a volume of 20mL.1 per plant. The nematode inoculation was carried out eight days after the sowing, using 2500 eggs per plant. Bioinputs were applied preventively and also as bioregulators of an existing nematodes population. Nine treatments, which corresponded to different moments of application of bioinputs in soil and soil plus vermocompost were evaluated. Results showed the lowest levels of infection when the Micosplag® bioinput was applied preventively (infection level of 6%), followed by the Tricho-D® treatment (infection 12%). There were statistical differences with the controls which were inoculated alone with the nematodes. When the two Bioinputs were applied preventively, they offered greater protection to the roots against nematodes. Dry weights of root and the aerial part of the plants showed the lowest values in treatments where the nematode was inoculated. Six months after the experiment was established, the three fungi that compose the Micosplag® Bioinput were isolated from the rhizosphere of the coffee plants.

RESUMEN El complejo Meloidogyne incognita y M. javanica ocasiona daños en las raíces de las plantas de café con pérdidas de su potencial productivo. El manejo tradicional contra este complejo se basa en el uso de moléculas químicas que han causado problemas en la salud del suelo y son nocivas para el medio ambiente. En condiciones de invernadero se evaluaron los insumos biotecnológicos Micosplag® (Paecilomyces lilacinus (Thom) Samson, 1974, Metarhizium anisopliae (Metsch) Sorokin y Beauveria bassiana (Balsamo) Vuillemin); y Tricho-D® (Trichoderma harzianum Rifai, 1969) en la protección de raíces de café contra el complejo de nematodos noduladores. Se empleó una dosis de 2g.L-1 de agua para Micosplag® y 10g. L-1 para Tricho-D® aplicando 20mL.1 por planta. La inoculación del nematodo se efectuó ocho días después de la siembra, empleando 2500 huevos por planta. Los Bioinsumos se aplicaron de manera preventiva y curativa. Se evaluaron nueve tratamientos, correspondientes a diferentes momentos de aplicación de los Bioinsumos en suelo y en suelo más lombricompuesto. Los niveles más bajos de infección se obtuvieron con el Bioinsumo Micosplag® de forma preventiva (infección de 6%), seguido de Tricho-D® (infección 12%). Hubo diferencias estadísticas con los testigos inoculados sólo con los nematodos. Los Bioinsumos de manera preventiva, ofrecieron mayor protección a las raíces contra los nematodos. Los pesos secos de raíz y parte aérea de las plantas registraron los valores más bajos donde se inóculo el nematodo. A los seis meses de establecido el experimento, en la rizósfera de las plantas de café se aislaron los tres hongos del Bioinsumo Micosplag.

Resumen Introducción. El cultivar de arroz INCA LP-7 es uno de los once cultivares principales de Cuba por su alto potencial de rendimiento, tolerancia a la salinidad y resistencia a patógenos. Sin embargo, no existen reportes sobre el aislamiento, identificación y caracterización de bacterias asociadas a este cultivar que promuevan su crecimiento. Objetivo. Seleccionar bacterias promisorias provenientes de la rizosfera del cultivar de arroz INCA LP-7 para promover el crecimiento del cultivo. Materiales y métodos. La investigación se realizó en el 2015 y el 2016 en el Instituto Nacional de Ciencias Agropecuarias, Cuba y en el Instituto de Investigaciones Biológicas Clemente Estable, Uruguay. Se aisló e identificó por secuenciación el gen 16SrNA bacterias asociadas al cultivar de arroz INCA LP-7. Se realizó una caracterización como bacterias promotoras del crecimiento vegetal y se estudió el efecto de la inoculación bacteriana en el crecimiento del arroz. Resultados. Se aislaron once bacterias rizosféricas de plantas de arroz del cultivar INCA LP-7. Un análisis filogenético mostró que por primera vez en Cuba se reportaron los géneros Pantoea, Acinetobacter y Mitsuaria asociados con el arroz. Los géneros Rhizobium y Enterobacter también fueron informados como bacterias rizosféricas del cultivar de arroz INCA LP-7. Algunos aislados solubilizan fosfatos inorgánicos y potasio, producen sideróforos y compuestos indólicos, tuvieron actividad exocelulasa y proteasa y forman biopelículas. La inoculación de aislados pertenecientes al género Pantoea provocaron un incremento de la altura, longitud de las raíces y biomasa de plantas de arroz en condiciones de invernadero. Conclusiones. Pantoea sp. GG1 y Pantoea sp. GG2, fueron las cepas más promisorias para la inoculación del cultivar de arroz INCA LP-7. Este es el primer informe en Cuba que aborda la caracterización de parte de la microbiota bacteriana asociada al cultivar de arroz cubano INCA LP-7 e informa a bacterias del género Pantoea como promotoras del crecimiento del cultivo.

Abstract Introduction. The rice cultivar INCA LP-7 is one of the eleven principal cultivars in Cuba due to their high yield potential, salinity tolerance, and pathogens resistance. However, there are not reports about the isolation, identification, and characterization of bacteria associated to this cultivar that promote its growth. Objective. To select promising bacteria from the rhizosphere of the INCA LP-7 rice cultivar to promote the crop growth. Materials and methods. The investigation was carried out in 2015 and 2016 at the Instituto Nacional de Ciencias Agropecuarias, Cuba and Instituto de Investigaciones Biologicas Clemente Estable, Uruguay. The 16SrNA gene of bacteria associated with the INCA LP-7 rice cultivar was isolated and identified by sequencing. Characterization was performed as plant growth promoting bacteria and the effect of bacterial inoculation on rice growth was studied. Results. Eleven rizopheric bacteria were isolated from rice plants of the INCA LP-7cultivar. A phylogenetic analysis showed that for the first time in Cuba Pantoea, Acinetobacter, and Mitsuaria genera were reported associated with rice. Rhizobium and Enterobacter genera were also informed as rhizospheric bacteria of INCA LP-7 rice cultivar. Some isolates solubilize inorganic phosphates and potassium, produce siderophores and indolic compound, had exo-celulase and protease activity and formed biofilm. The inoculation of isolates belonging to Pantoea genus produced an increase in height, root length, and biomass of rice plants under greenhouse conditions. Conclusions. Pantoea sp. GG1 and Pantoea sp. GG2 were the most promising strains for the inoculation of the INCA LP-7 rice cultivar. This is the first report in Cuba that focuses on the characterization of the bacterial microbiota part associated to Cuban rice cultivar INCA LP-7 and reports bacteria of the Pantoea genus as crop growth promoters.