Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Background. Caseous lymphadenitis is a worldwide distribute disease that affects the sheep and goat industry. Corynebacterium pseudotuberculosis ovis is a facultative intracellular Gram-positive bacterium, considered the etiologic agent of the disease. Complete genome sequences of Mexican isolates have been obtained and different strain has been previously characterized. The study of virulence factors allows establishing potential candidates for the development of vaccines and diagnostic tools. Objective. To identify the complete pld and cp40 genes sequence from a Mexican isolate of Corynebacterium pseudotuberculosis ovis, principal virulence factors. Methodology. Corynebacterium pseudotuberculosis isolate 2J-L was obtained from an abscess of a sheep of the State of Jalisco. The complete pld and cp40 genes were amplified by PCR, cloned into a replicative vector and sequenced by Sanger automatic sequencing. Gene sequences conservancy was established, analyzing homology across previously reported genes of Mexican strains MEX1, MEX2, MEX9, MEX25 and MEX29. Results. Sequences of pld and cp40 genes from isolate 2J-L presented high percentages of similarity (99%) in comparison with the sequences of other isolates of Corynebacterium pseudotuberculosis, reported in the GenBank database. The analysis of nucleotide sequence homology and phylogenetic tree based on pld and cp40 directed the observation that 2J-L is related to Mexican strain MEX29 and MEX25. Phylogenetic results agreed on the idea that strains biovar ovis and biovar equi are groupings on different clades. Finally, results indicate that Mexican strains are more similar among strains isolated from the same host type, without geography distance influence. Implications. The analysis pointed out that both genes conserve their sequences in comparison with Mexican and international strains, which encourages the research continuity for vaccine and diagnostic tools development using proteins PLD and CP40 as antigen targets. Conclusions. The complete pld and cp40 genes from Mexican isolate 2J-L were amplified, cloned and analyzed; important virulence factors from Corynebacterium pseudotuberculosis.

Background: The Potyvirus Papaya ringspot virus type P (PRSV-p) causes the papaya (Carica papaya L.) ringspot disease, which causes damage to the plantations of this crop. In regions where there is movement of plant material and continuous production processes, there is greater genetic variability of this virus; such is the case of the State of Veracruz, Mexico, one of the main papaya producers in the country. Objective: To analyze the genetic variability of isolates of PRSV-p, present in commercial papaya plantations in the central zone of the State of Veracruz. Methodology: Leaves with differential symptoms of the disease were collected. The capsid protein (CP) coding region was amplified by RT-PCR to confirm the identity of the virus. The sequences obtained were analyzed, aligned and a phylogenetic tree was obtained. Results: The presence of PRSV-p was confirmed by RT-PCR. Through sequence analysis, high diversity was observed in the first 50 amino acids encoded in the N-terminal region of CP. In the phylogenetic tree, three viral genetic groups were obtained. The largest conserved sites of interest (even the WCIEN box and QMKAAA) were found near the C-terminal region of the CP. 100% homology was observed in the central and C-terminal region of the Ver75Co isolate, with respect to the consensus sequence. Implications: The results show the genetic diversity of the virus in the central zone of the state of Veracruz, which will allow genetic modifications to improve resistance in papaya plants. Conclusions: There is genetic variability of PRSV-p in Veracruz, there are conserved sites of interest (WCIEN and QMKAAA) and changes in the N-terminal region, which includes the EK repetitive region and the DAG codon. These changes may be a genetic characteristic of the virus for adaptation. The Ver75Co isolate may be the point of change that gives rise to the other isolates of this work. The phylogenetic tree shows a single genetic group of the virus, which is distributed in three different clades.

Antecedentes. El estrés salino de los suelos del trópico afecta el crecimiento y la composición nutritiva de los pastos, como consecuencia se afecta la disponibilidad y calidad de forraje para el ganado. La salinidad puede reducir el contenido de proteína cruda y aumentar la proporción de fibra detergente neutra (FDN) de los pastos. Lo anterior puede disminuir la degradabilidad ruminal, las poblaciones microbianas, y alterar la producción de ácidos grasos volátiles (AGV) que son la principal fuente de energía para los rumiantes. Por otra parte, un aumento de FDN en los pastos puede incrementar la emisión de metano (CH4). Por tal motivo, se requiere generar información suficiente sobre la calidad nutritiva de los pastos cultivados en suelos salinos y sus patrones de fermentación ruminal. Objetivo. Evaluar los pastos híbridos del género Urochloa, Cayman y Cobra crecidos en cinco concentraciones de salinidad, para determinar su efecto durante la fermentación ruminal in vitro, sobre la composición química, degradabilidad, parámetros de fermentación, microorganismos ruminales, en la producción de CH4 y CO2. Metodología. Se evaluaron cinco tratamientos experimentales: niveles de salinidad, para ambos pastos de 0, 2, 4, 6, 10 dS m-1 de NaCl. A los dos pastos experimentales se les determinó la composición química, y posteriormente fueron incubados in vitro en medio de cultivo para bacterias totales con adición de fluido ruminal fresco, para determinar degradabilidad de materia seca (DIVMS), parámetros de fermentación ruminal, poblaciones microbianas y producción de biogás. Resultados. El pasto Cayman presentó mayor (P<0.05) contenido de ceniza y extracto etéreo a CE ≥ 4 dS m-1; sin embargo, disminuyó su contenido de proteína cruda. En el pasto Cobra también se presentó reducción de proteína a 10 dS m-1. En ambos pastos DIVMS, producción de AGV y de CH4 no fueron afectados por la salinidad, ni se presentaron cambios en el conteo de microorganismos ruminales. Implicaciones. Los resultados del presente estudio evalúan el efecto de la salinidad sobre el contenido de proteína cruda y paredes celulares de los pastos Cayman y Cobra crecidos en estrés salino. Se determinó que la salinidad no afecta la degradabilidad ni los patrones de fermentación ruminal de los pastos estudiados. Conclusiones. Con nivel de salinidad de 10 dS m-1 la proteína de los pastos Cayman y Cobra disminuyó 8.42% y 18.0%, respectivamente. Los niveles de salinidad estudiados no afectan no afectan DIVMS, población microbiana, ni producción de CH4 durante la fermentación ruminal in vitro de las especies evaluadas.

Background: Crop microbial pathogens reduce the production and quality of agricultural products. They cause substantial increase costs for producers of fruits, vegetables, and ornamental plants with negative consequences on economy and food security at household, national and global levels. Annually, the losses represent around 40% to 50% for root crops, vegetables, and fruits. Chemical control with fungicides can prevent, kill, mitigate, or inhibit the growth of plant pathogenic fungi. Nevertheless, biological control with microorganisms and natural molecules is an increasingly popular alternative to protect crops. Objective: Here, the antagonist activity of soil Streptomyces sp. Y20 against the pathogenic fungi causing diseases in plants and fruits was evaluated. Methodology: Streptomycetes bacteria was isolated from soils collected at open field cultures of local farms with tomato. The antagonism was evaluated in vitro via a dual confrontation experiment against fungal species of Fusarium, Lasiodiplodia, Colletotrichum, Aspergillus, Botrytis, and Sclerotium. Streptomyces sp. Y20 was characterized phenotypically and molecularly identified by the 16S rDNA gene. The biosynthetic gene clusters for polyketide synthases (PKS Type I) and non-ribosomal peptide synthase (NSPS) were detected. Results: Preliminary, the isolate Y20 was selected by the higher antagonism against F. oxysporum f sp. lycopersici. Taxonomic characterization of the isolate Y20 by the analysis of the 16S rDNA sequence led to its identification as member of Streptomyces genus. Spore surface morphology by Scanning Electronic Microscopy (SEM) showed barrel-like spores. Antagonistic activity of Streptomyces sp Y20 was comparable to the commercial strain S. lydicus WYEC108 (P > 0.5). However, there was a superior antagonism of Y20 strain versus the commercial strain WYEC108 against F. oxysporum f sp. lycopersici, Fusarium sp. CDBB1172, F. oxysporum, Lasiodiplodia sp., and Aspergillus sp. (P < 0.05). Implications: Soil streptomycetes with in vitro antagonistic activity on plant pathogenic fungi could be a natural alternative to the use of chemical fungicides to control plant diseases. Conclusion: This study presented a novel soil Streptomyces specie which showed in vitro antagonism against a diversity of plant pathogenic fungal species. Streptomyces strain Y20 could be used as a biocontrol agent.

Background. Wheat is a staple food crop and easily accessible to the population, so the biofortification of wheat grains is substantial to mitigate malnutrition. Objective. To evidence and select wheat genotypes based on nutritional multi-characters of grains based on genetic parameters. Methodology. Experiments were carried out in the 2019 agricultural season in five wheat areas of the state of Rio Grande do Sul, in two sowing seasons, in the municipalities of Cachoeira do Sul, Cruz Alta, Santo Augusto, São Gabriel and Vacaria. The experimental design was randomized blocks, organized in a factorial scheme with 10 cultivation environments (5 sites by two sowing dates) and 30 genotypes, with three replications. To carry out the selection of genotypes, the WAASB, AMMI, GGE and BLUP methodologies were applied. Results. In terms of lipids and fibers, three mega environments were formed, highlighting the genotypes BRS 327, CD 1550, Ametista, CD 1303 and BRS 331, respectively. For mineral material, there was the formation of two mega environments and the genotypes that stood out were Quartz and Tbio Toruk, while for carbohydrate there was the formation of a mega environment and the genotype that stood out was CD 1550. The Tbio Mestre and LG Prisma genotypes were the ideal genotypes, with high performance in the Cachoeira do Sul environment – Sowing 2nd fortnight. Tbio Iguaçú expressed high levels of lipids in Santo Augusto – Seeding 1st fortnight, São Gabriel – Seeding 2nd fortnight and Vacaria – Seeding 2nd fortnight. ORS 1405 and Tbio Iguaçú expressed high levels of carbohydrates in the Vacaria - Seeding 2nd fortnight environment. Heritabilities without interaction effects were high, which characterizes high genotypic additive variance. Implications. The current results indicate that there is genetic variability, making it possible to select genotypes with greater expression of nutrients in the grains. Conclusion. The TBio Mestre, CD 1440, LG Prisma and Marfim genotypes expressed greater performance and stability of the evaluated traits.

The Laja River basin is located between parallels 21° 32' 58", 20° 16'14" N, and meridians - 100° 6' 28'' - 101° 30'44" W. In 2014, the basin was classified with a high degree of pressure on the water resource (Conagua, 2014). It also ranked second as an administrative hydrological region with the highest population density, and it presents strong problems with supply and demand. All the previous reasons motivated this work. The objective was to calibrate, validate and estimate runoff surface, considering the effects of changes in precipitation, Therefore, hydrological modeling was performed in WEAP (Water Evaluation and Planning) using the soil moisture method. The information used was on soil use and physical characteristics; crop coefficients; average monthly data on precipitation; average temperatures; relative humidity; and wind speed. The calibration and validation processes were carried out at four points in the basin, for five years on a monthly period. The hydrometric stations were Puente Dolores, Begoña II, Tres Guerras and Pericos. For each station, the coefficient of determination (r2) and Nash-Sutcliffe efficiency index (NSE) were estimated. The values obtained in the calibration phase were an r2 of 0.8 to 0.82 and NSE from 0.55 to 0.77. In the validation phase, the values for r2 range from 0.65 to 0.86 and NSE from 0.57 to 0.75. Climate information was generated with WGEN for 10 years, to generate runoff scenarios, with the RCP8.5 projections, for the period 2012-2022. In conclusion, WEAP is a software capable of correctly simulating, with the soil moisture method, the response of the Laja River basin. WEAP correctly simulated flows measured in the gauging station with an average absolute error of less than 10 %.

La ecuación de Richards se utiliza para modelar la infiltración y el movimiento de agua en suelos, u otro medio poroso. Esta ecuación, junto con las complejas ecuaciones constitutivas que caracterizan al suelo, resulta en un sistema de ecuaciones no lineales en derivadas parciales. En este trabajo, la ecuación de Richards se escribe en función del grado de saturación del suelo, y se resuelve por medio de un método explícito en diferencias finitas. El potencial matricial se obtiene como una función del grado de saturación y la convergencia de las soluciones numéricas se analiza por medio del procedimiento de von Neumann. Como resultado, se obtiene una expresión analítica para determinar si una simulación es estable con pasos temporales y espaciales dados. A partir de estos parámetros de simulación y las propiedades del suelo, se definen números adimensionales para generalizar el método propuesto.

The effects of the oil industry continue to cause damage today. For example, car washers and their components still pollute sewage. This work assesses the efficiency of an artisan filter made of sugarcane bagasse, sand, crushed brick, and pumice stone. The research was carried out in the Chemistry Laboratory of the Faculty of Civil and Mechanical Engineering of the Technical University of Ambato, Ecuador, and as effluent, wastewater from a small car washing machine was used. To prove the efficiency of the filter and its limitations, the variation index in different parameters of this water was measured for 31 days, such as total solids, total suspended solids, BOD5 (biological oxygen demand), COD (chemical oxygen demand), pH, oils and fats, turbidity and TPH (total petroleum hydrocarbons). The preliminary results showed a significant improvement in the treated effluent's quality, especially in turbidity, TPH, total suspended solids, and pH.