Characterization of Actinobacterial Strains as Potential Biocontrol Agents against Macrophomina phaseolina and Rhizoctonia solani, the Main Soil-Borne Pathogens of Phaseolus vulgaris in Cuba

Macrophomina phaseolina and Rhizoctonia solani are considered two major soil-borne pathogens of Phaseolus vulgaris in Cuba. Their management is difficult, not only due to their intrinsic biology as soil-borne pathogens, but also because the lack of active ingredients available against these pathogens. Actinobacteria, a heterogeneous bacterial group traditionally known as actinomycetes have been reported as promising biological control agents (BCAs) in crop protection. Thus, the main objective of this study was to evaluate the effectiveness of 60 actinobacterial strains as BCAs against M. phaseolina and R. solani in vitro by dual culture assays. The most effective strains were characterized according to their cellulolytic, chitinolytic and proteolytic extracellular enzymatic activity, as well as by their morphological and biochemical characters in vitro. Forty and 25 out of the 60 actinobacteria strains inhibited the mycelial growth of M. phaseolina and R. solani, respectively, and 18 of them showed a common effect against both pathogens. Significant differences were observed on their enzymatic and biochemical activity. The morphological and biochemical characters allow us to identify all our strains as species belonging to the genus Streptomyces. Streptomyces strains CBQ-EA-2 and CBQ-B-8 showed the highest effectiveness in vitro. Finally, the effect of seed treatments by both strains was also evaluated against M. phaseolina and R. solani infections in P. vulgaris cv. Quivicán seedlings. Treatments combining the two Streptomyces strains (CBQ-EA-2 + CBQ-B-8) were able to reduce significantly the disease severity for both pathogen infections in comparison with the non-treated and inoculated control. Moreover, they showed similar effect than that observed for Trichoderma harzianum A-34 and with Celest® Top 312 FS (Syngenta®; Basilea, Switzerland) treatments, which were included for comparative purposes

UTILIZACIÓN DE STREPTOMYCES SP. RL8 COMO AGENTE PROBIÓTICO EN POLLOS DE LA RAZA LEGHORN

Durante sus primeras semanas de vida los pollos de las instalaciones avícolas están sometidos a situaciones de estrés que ocasionan desbalances en la microbiota intestinal, que hacen a su vez que sean susceptibles a la incidencia de microorganismos patógenos. El uso de antibióticos de amplio espectro para contrarrestar los efectos de dichos patógenos ha originado problemas de resistencia bacteriana y de inocuidad alimentaria. Se ha propuesto la utilización de probióticos como un medio para la reducción de patógenos intestinales y aumento de indicadores bioproductivos. En el presente trabajo se evaluó la actividad probiótica de Streptomyces sp. cepa RL8 en indicadores fisiológicos y productivos en pollos de la raza Leghorn. Se demostró que no hubo diferencias significativas entre el grupo tratado y el grupo control en cuanto a los parámetros productivos y de salud. Sin embargo, se encontraron diferencias significativas entre ambos grupos para algunos componentes hematológicos e inmunológicos. Por tanto, la cepa de Streptomyces sp. RL8 puede ser una alternativa para mejorar el estado de salud de los pollos, a través de la estimulación de parámetros hematológicos y modulación del sistema inmune de las aves

Behavior of 15 strains of mycorrhizal fungi (hma) on the development of coffee seedlings in a soil gleyed brown.

CONTENIDO Bosque universitario El Caimital y la estación silvicultural El Manguito: dos lotes boscosos de los llanos occidentales para la conservación in situ de especies en peligro. The Caimital university forest and the Manguito silvicultural station: two forest areas of the Venezuelan western plains for in situ conservation of endangered species. Arends, Ernesto; Sánchez P., Domingo A.; Villarreal, Alberto; Serrano P., Julio C. y Benítez, María E. Consideraciones teórico - metodológicas sobre la ordenación del territorio. Theoretical-methodological considerations on land use planning. Briceño Méndez, Manuel Indicadores ambientales derivados de los cambios en las cubiertas artificiales (1987 - 1997). Comunidad de Madrid, España. Environmental indicators derived from the artificial cover changes (1987 - 1997). Madrid community, Spain. Aldana, Angnes Teresa Establecimiento de la cubierta vegetal en áreas degradadas (principios y métodos). Vegetative coves establishment in degraded areas (principles and methods). Rondón Rangel, José Armando y Vidal, Raúl Comportamiento de 15 cepas de hongos micorrizogenos (hma) sobre el desarrollo de posturas de cafeto en un suelo pardo gleyzoso. Behavior of 15 strains of mycorrhizal fungi (hma) on the development of coffee seedlings in a soil gleyed brown. Sánchez, Ciro; Montilla, Eugenio; Rivera, Ramón y Cupull, René Validación del modelo Leachm para predecir la salinidad en un suelo del valle de Quibor, con cultivo de cebolla bajo riego localizado. Validation of the model Leachm to predict the salinity in a soil of the valley de Quibor, in the onion crop under drip irrigation. Rázuri R., Luis R.; Linares D., José G.; Rosales, José G.; Romero C., Edgar y Hernández, José [email protected]@[email protected]@inca.edu.cuNivel analíticosemestra

Rhizobium isolated effect on phenotypic parameters and nitrogen fixation in common bean genotypes (Phaseolus vulgaris L.)

The present work was carried out with the aim to determine the effect of Rhizobium isolates previously characterized and genetically identified on morphological and physiological parameters and the nitrogen fixation of common bean genotypes. The phenotypic analysis of isolates carried out under controlled conditions, where the nodulation, morphological and physiological parameters and the nitrogen fixation of the genotypes ICA Piajo and BAT-304 were evaluated. The results showed that the isolated strains have the ability for abundant nodule formation in roots plant of both genotypes analyzed. The remarkable beneficial effect was for R. etli specie and the isolates from Santa Clara and Camajuaní-1, as well as the isolated of R. pisi from Camajuaní-2. The genotypic variability showed the close positive correlation among these strains and the genotype BAT-304 compared with ICA Pijao

Antagonistic activity Trichoderma harzianum Rifai on the causal agent of rice blast (Pyricularia grisea Sacc.)

With the objective to evaluate the antagonistic activity of T. harzianum (strain A-34) on the causal agent of rice blast (P. grisea), were developed several in vitro experiments. It was evaluated the biocontrol mechanisms such as competition through mounted the percent inhibition of radial growth of hyphae of P. grisea from 24 to 240 hours and the antagonistic capacity. In addition, was evaluated micoparasitism to inclination the observation of events Microscopy winding, penetration, vacuolization, lysis, and antibiosis by observing 24 hours a confrontation between the hyphae of the phytopathogenic fungus and biological control agent. It was obtained at 120 hours 100 % inhibition of micelial growth of causal agent, what corresponded with the degree 1 of antagonistic capacity (scale) and is recorded as a hyperparasitic action on P. grisea. It was evidenced an antibiotic effect of metabolites produced by T. harzianum (strain A-34) to 24 hours of confrontation, where there was time interaction between the hyphae of microorganisms with 14,3 % inhibition, also was evidence the micoparasitism events by penetration, vacuolization and lysis in the cells of phytopathogenic fungus. These results demonstrated the ability of T. harzianum (strain A-34) on causal agent of rice blast (P. grisea)

Influence of incubation time of Trichoderma harzianum Rifai and antifungal activity of culture filtrate against Bipolaris oryzae

This work was developed at Agriculture Microbiology laboratory in the Agriculture Faculty at Universidad Central “Martha Abreu” de Las Villas, with the aim to evaluate the influence of incubation time of Trichoderma harzianum Rifai on antifungal activity of its culture filtrates against Bipolaris oryzae. Flask with Czapek broth was used for growing T. harzianum, then one disc of mycelium were incubated during 20 and 30 days at 28±1ºC and dark. Trichoderma harzianum (strain A-34) was submited to filtration process, and comparison were done among concentration of 0%, 25%, 50%, 75%, 100% (v/v). Major inhibition porcentaje were observed in concentrations of 75% y 100% both at 20 and 30 days of incubation. At 20 day the inhibition porcentaje was greater in comparsison with 30 days

Selección de cepas de actinomicetos para el control de Rhizoctonia solani Kühn, Sclerotium rolfsii Sacc y Macrophomina phaseolina (Tassi) Goid en frijol común (Phaseolus vulgaris L.)

Con el objetivo de seleccionar cepas de actinomicetos eficientes como agentes biocontroladores de los hongos fitopatógenos del suelo Rhizoctonia solani Kühn., Sclerotium rolfsii Sacc. y Macrophomina phaseolina (Tassi) Goid., se evaluaron 69 cepas de actinomicetos, a las cuales se le determinó la actividad antagonista in vitro contra los hongos fitopatógenos del suelo. Posteriormente, se realizó una selección de las cepas con mejor capacidad antagónica para la evaluación de la actividad enzimática extracelular, la capacidad solubilizadora de fosfatos, la producción de ácido indol-acético (AIA) y la caracterización molecular. De las 69 cepas evaluadas, se obtuvo que 2 cepas presentaron antagonismo contra S. rolfsii, 39 contra M. phaseolina y 11 contra R. solani. Las cepas que presentaron los mayores halos de inhibición contra R. solani fueron J11, J4 y EA2, y contra M. phaseolina la cepa EBa21. Todas las cepas seleccionadas presentaron actividad enzimática extracelular; se destacan la cepa EBa21 en la producción de quitinasas, las cepas EA2, J4 y L2 en la de celulasas y las cepas EA2 y B8 en las de proteasas. En la solubilización de fosfato sobresalieron las cepas B8 y EBa21, mientras que en la producción de AIA prevalecieron las cepas EBe3, EA2 y EBa21. La identificación de las cepas, mediante la secuenciación de la región 16S del ARNr, arrojó que todas tienen una homología del 99% con diferentes especies de Streptomyces