Simulation of soil organic carbon changes in crop systems with castor bean using the RothC model

El objetivo del presente trabajo fue la simulación de los cambios del carbono orgánico del suelo (COS), por el modelo RothC, en razón del cambio de uso de suelo del sistema tradicional – asociación maíz‑calabaza (TMC) – a sistemas con higuerilla (Ricinus communis): multiestratos (MUL), callejones (CALL) y monocultivo de higuerilla (HIG). Las simulaciones del COS se hicieron para las profundidades de suelo 0–20 y 0–40 cm, para el periodo de 1980–2040, considerándose como línea base al sistema TMC. Las tasas de cambio de COS estimadas con el RothC, en ambas profundidades de suelo, estuvieron en 0,5–1,2, 0,4–0,8, 0,3–0,5 y 0,04–0,1 Mg ha-1 de C por año en los sistemas HIG, MUL, CALL y TMC, respectivamente, y fueron consistentes con las reportadas en la literatura. El desempeño del RothC tuvo 89% de eficiencia (EF), con R2=0,9, lo que muestra que este modelo puede usarse con información temporal del COS escasa, información de la historia de uso de suelo y mediciones de la entrada de residuos vegetales aéreos y subterráneos en el suelo.The objective of this work was to simulate, by the RothC model, the changes in soil organic carbon (SOC) caused by changes of land use – from the traditional maize‑squash (TMC) association to systems with castor bean (Ricinus communis): multilayer (MUL), alleys (CALL) and monoculture (HIG). SOC simulations were performed for 0–20 and 0–40 cm soil depths, for the period 1980–2040, considering the TMC system as the base line. SOC change rates estimated with RothC, for both soil depths, were 0.5–1.2, 0.4–0.8, 0.3–0.5 and 0.04–0.1 Mg ha-1 C per year in the HIG, MUL, CALL and TMC systems, respectively, and were consistent with those reported in the literature. RothC perfomance had 89% efficiency (EF) and R2 = 0.9, which shows that this model can be used with scarce SOC temporal information, information on the history of land use, and with input measurements of aerial and underground plant residues in the soil

A serralysin-like protein of Candidatus Liberibacter asiaticus modulates components of the bacterial extracellular matrix

Huanglongbing (HLB), the current major threat for Citrus species, is caused by intracellular alphaproteobacteria of the genus Candidatus Liberibacter (CaL), with CaL asiaticus (CLas) being the most prevalent species. This bacterium inhabits phloem cells and is transmitted by the psyllid Diaphorina citri. A gene encoding a putative serralysin-like metalloprotease (CLIBASIA_01345) was identified in the CLas genome. The expression levels of this gene were found to be higher in citrus leaves than in psyllids, suggesting a function for this protease in adaptation to the plant environment. Here, we study the putative role of CLas-serralysin (Las1345) as virulence factor. We first assayed whether Las1345 could be secreted by two different surrogate bacteria, Rhizobium leguminosarum bv. viciae A34 (A34) and Serratia marcescens. The protein was detected only in the cellular fraction of A34 and S. marcescens expressing Las1345, and increased protease activity of those bacteria by 2.55 and 4.25- fold, respectively. In contrast, Las1345 expressed in Nicotiana benthamiana leaves did not show protease activity nor alterations in the cell membrane, suggesting that Las1345 do not function as a protease in the plant cell. Las1345 expression negatively regulated cell motility, exopolysaccharide production, and biofilm formation in Xanthomonas campestris pv. campestris (Xcc). This bacterial phenotype was correlated with reduced growth and survival on leaf surfaces as well as reduced disease symptoms in N. benthamiana and Arabidopsis. These results support a model where Las1345 could modify extracellular components to adapt bacterial shape and appendages to the phloem environment, thus contributing to virulence

Insights from the genome of the biotrophic fungal plant pathogen Ustilago maydis

Ustilago maydis is a ubiquitous pathogen of maize and a well-established model organism for the study of plant-microbe interactions. This basidiomycete fungus does not use aggressive virulence strategies to kill its host. U. maydis belongs to the group of biotrophic parasites (the smuts) that depend on living tissue for proliferation and development. Here we report the genome sequence for a member of this economically important group of biotrophic fungi. The 20.5-million-base U. maydis genome assembly contains 6,902 predicted protein-encoding genes and lacks pathogenicity signatures found in the genomes of aggressive pathogenic fungi, for example a battery of cell-wall-degrading enzymes. However, we detected unexpected genomic features responsible for the pathogenicity of this organism. Specifically, we found 12 clusters of genes encoding small secreted proteins with unknown function. A significant fraction of these genes exists in small gene families. Expression analysis showed that most of the genes contained in these clusters are regulated together and induced in infected tissue. Deletion of individual clusters altered the virulence of U. maydis in five cases, ranging from a complete lack of symptoms to hypervirulence. Despite years of research into the mechanism of pathogenicity in U. maydis, no 'true' virulence factors had been previously identified. Thus, the discovery of the secreted protein gene clusters and the functional demonstration of their decisive role in the infection process illuminate previously unknown mechanisms of pathogenicity operating in biotrophic fungi. Genomic analysis is, similarly, likely to open up new avenues for the discovery of virulence determinants in other pathogens. ©2006 Nature Publishing Group.J.K., M. B. and R.K. thank G. Sawers and U. Kämper for critical reading of the manuscript. The genome sequencing of Ustilago maydis strain 521 is part of the fungal genome initiative and was funded by National Human Genome Research Institute (USA) and BayerCropScience AG (Germany). F.B. was supported by a grant from the National Institutes of Health (USA). J.K. and R.K. thank the German Ministry of Education and Science (BMBF) for financing the DNA array setup and the Max Planck Society for their support of the manual genome annotation. F.B. was supported by a grant from the National Institutes of Health, B.J.S. was supported by the Natural Sciences and Engineering Research Council of Canada and the Canada Foundation for Innovation, J.W.K. received funding from the Natural Sciences and Engineering Research Council of Canada, J.R.-H. received funding from CONACYT, México, A.M.-M. was supported by a fellowship from the Humboldt Foundation, and L.M. was supported by an EU grant. Author Contributions All authors were involved in planning and executing the genome sequencing project. B.W.B., J.G., L.-J.M., E.W.M., D.D., C.M.W., J.B., S.Y., D.B.J., S.C., C.N., E.K., G.F., P.H.S., I.H.-H., M. Vaupel, H.V., T.S., J.M., D.P., C.S., A.G., F.C. and V. Vysotskaia contributed to the three independent sequencing projects; M.M., G.M., U.G., D.H., M.O. and H.-W.M. were responsible for gene model refinement, database design and database maintenance; G.M., J. Kämper, R.K., G.S., M. Feldbrügge, J.S., C.W.B., U.F., M.B., B.S., B.J.S., M.J.C., E.C.H.H., S.M., F.B., J.W.K., K.J.B., J. Klose, S.E.G., S.J.K., M.H.P., H.A.B.W., R.deV., H.J.D., J.R.-H., C.G.R.-P., L.O.-C., M.McC., K.S., J.P.-M., J.I.I., W.H., P.G., P.S.-A., M. Farman, J.E.S., R.S., J.M.G.-P., J.C.K., W.L. and D.H. were involved in functional annotation and interpretation; T.B., O.M., L.M., A.M.-M., D.G., K.M., N.R., V. Vincon, M. VraneŠ, M.S. and O.L. performed experiments. J. Kämper, R.K. and M.B. wrote and edited the paper with input from L.-J.M., J.G., F.B., J.W.K., B.J.S. and S.E.G. Individual contributions of authors can be found as Supplementary Notes

Taller de concordancia en la evaluación de imágenes capilaroscópicas

Introducción: la capilaroscopia es un método no invasivo que permite observar la microvasculatura en el área periungueal. Los resultados informados pueden ser altamente variables entre distintos observadores. A lo largo del tiempo surgieron métodos cuantitativos y semicuantitativos para mejorar la reproducibilidad. Objetivos: conocer el nivel de acuerdo intra e interobservador al informar los diferentes patrones capilaroscópicos en individuos con diferente nivel de entrenamiento. Materiales y métodos: estudio de corte transversal. Participaron médicos reumatólogos especialistas y en formación que habían realizado previamente un curso virtual de capacitación en capilaroscopia. Recibieron 40 imágenes capilaroscópicas proyectadas en una presentación de PowerPoint y debían responder a través de un cuestionario digital. Se evaluó la concordancia de respuestas intra e interobservador. Resultados: se encontró un alto nivel de concordancia global con un kappa 0,66 IC 95% (0,63-0,70) p<0,0000. También en otros grupos como reumatólogos en formación: kappa 0,65 IC 95% (0,60-0,71) p=0,0000, y médicos reumatólogos: kappa 0,67 IC 95% (0,62-0,72) p=0,0000. Conclusiones: el nivel de concordancia encontrado fue globalmente alto, independientemente del nivel de entrenamiento de los profesionales, y de ser o no reumatólogo. La concordancia fue superior cuando se comparó a quienes tenían más de 4 años de experiencia en la realización de videocapilaroscopia

Desempeño del modelo rothc-26.3 a nivel de parcela en México

De acuerdo con el Panel Intergubernamental sobre el Cambio Climático (PICC), deben reportarse los almacenes y cambios del carbono orgánico del suelo (COS) en el tiempo. El modelo RothC-26.3 (RothC) es uno de los más usados en el mundo para estudiar la dinámica del C en diferentes sistemas. Se evaluó el desempeño del RothC en la simulación de los cambios del COS, a nivel de parcela, en experimentos de corta duración. Se evaluaron nueve sitios y los sistemas: agrícola con residuos vegetales (A+R), agrícola sin residuos (A-R), forestales (F), praderas (PR) y agostaderos (AGOS). Las parcelas experimentales se ubicaron en los estados de México, Tlaxcala, Michoacán, Guanajuato, Oaxaca, Jalisco y Nuevo León. El RothC se ejecutó (i) con el COSinicial, medido en cada punto de muestreo (*CIPUN) en parcelas de la Sierra Norte de Oaxaca y, (ii) con el COSinicial promedio medido por parcela (*CIPAR) en el resto de los sitios. Se midieron y estimaron los parámetros de entrada al modelo, como residuos vegetales y abonos orgánicos. El grado de asociación entre el COS medido y el simulado fue de 0.76 y hasta 1.0 en todos los sitios. La eficiencia del modelo (EF) varió entre 0.53 y 0.93, excepto en el Batán, donde se evaluaron sistemas de labranza (EF= −0.60). La r, en ambas formas de simulación, varió entre 0.63 y 0.97, excepto en AGOS; EF en los agrícolas fue de 0.48 a 0.84 y de 0.81 en F *CIPAR. La EF fue insatisfactoria obtenida para los AGOS (*CIPAR) y forestales y praderas (*CPUN). Considerando los resultados de los sitios y sistemas y, la forma de simulación *CIPAR, el modelo RothC se puede usar con buena aceptación para simular los cambios de COS a nivel de parcela en los sistemas agrícolas y forestales, mediana en praderas y baja en agostaderos

Simulation of soil organic carbon changes in Vertisols under conservation tillage using the RothC model

The purpose of this study was to determine the measured and simulated rates of soil organic carbon (SOC) change in Vertisols in short-term experiments when the tillage system is changed from traditional tillage (TT) to conservation tillage (CT). The study was conducted in plots in four locations in the state of Michoacán and two locations in the state of Guanajuato. In the SOC change simulation, the RothC-26.3 carbon model was evaluated with different C inputs to the soil (ET1-ET5). ET was the measured shoot biomass (SB) plus estimated rhizodeposition (RI). RI was tested at values of 10, 15, 18, 36 and 50 % total biomass (TB). The SOC changes were simulated with the best trial where ET3 = SB + (0.18*TB). Values for model efficiency and the coefficient of correlation were in the ranges of 0.56 to 0.75 and 0.79 to 0.92, respectively. The average rate of SOC change, measured and simulated, in the study period was 3.0 and 1.9 Mg ha−1 yr−1, respectively; later, in a simulation period of 45 years, SOC change was 1.2 ± 0.8. In particular, without making adjustments in the RothC parameters and with information on measured plant residue C inputs to the soil, it was possible to simulate changes in SOC with RothC and estimate trends over a period of more than 45 years

Cambios de carbono orgánico del suelo bajo escenarios de cambio de uso de suelo en México

Information regarding changes in soil organic carbon (SOC) due to change in land use of secondary vegetation tillage systems, scrub or grassland in Mexico is meager. This study was attended in 2011, at sites located in the States of Mexico, Hidalgo, Tlaxcala and Veracruz, in order to estimate changes in SOC under different scenarios of change in land use systems with secondary vegetation tillage systems, scrub or grassland, using the Rothamsted Carbon Model (RothC). The simulations were performed for a period of 40 years, taking into account: specific measurements of SOC in the study sites, the estimated C input into the soils of the plant residues and fertilizers, and the evaluation of RothC performance in sites and systems of Mexico. According to the results of simulation of scenarios of land use change, the use of conservation tillage systems under irrigated or rainfed conditions is the best alternative to conserve SOC stores and avoid loss of this element as CO2 emissions.La información de los cambios del carbono orgánico del suelo (COS) debido al cambio de uso de suelo de vegetación secundaria a sistemas de labranza, matorrales o pastizales en México es escasa. El presente estudio se condujo en 2011 en sitios ubicados en los estados de México, Hidalgo, Tlaxcala y Veracruz, con el propósito de estimar los cambios del COS bajo diferentes escenarios de cambio de uso de suelo de los sistemas con vegetación secundaria a sistemas de labranza, matorrales o pastizales, usando el modelo de simulación de carbono RothC. Las simulaciones se realizaron para un periodo de 40 años tomando en cuenta: las mediciones puntuales de COS en los sitios de estudio, la entrada estimada de C al suelo de los residuos vegetales y abonos, y la evaluación del desempeño del modelo RothC en sitios y sistemas de México. De acuerdo con los resultados de simulación de escenarios de cambio de uso de suelo, el uso de sistemas de labranza de conservación bajo condiciones de riego o temporal, es la mejor alternativa para conservar los almacenes de COS y evitar pérdida de este elemento como emisiones de CO2

Simulación de los cambios de carbono orgánico del suelo en sistema de cultivo con higuerilla por el modelo RothC Simulation of soil organic carbon changes in crop systems with castor bean using the RothC model

El objetivo del presente trabajo fue la simulación de los cambios del carbono orgánico del suelo (COS), por el modelo RothC, en razón del cambio de uso de suelo del sistema tradicional - asociación maíz-calabaza (TMC) - a sistemas con higuerilla (Ricinus communis): multiestratos (MUL), callejones (CALL) y monocultivo de higuerilla (HIG). Las simulaciones del COS se hicieron para las profundidades de suelo 0-20 y 0-40 cm, para el periodo de 1980-2040, considerándose como línea base al sistema TMC. Las tasas de cambio de COS estimadas con el RothC, en ambas profundidades de suelo, estuvieron en 0,5-1,2, 0,4-0,8, 0,3-0,5 y 0,04-0,1 Mg ha-1 de C por año en los sistemas HIG, MUL, CALL y TMC, respectivamente, y fueron consistentes con las reportadas en la literatura. El desempeño del RothC tuvo 89% de eficiencia (EF), con R²=0,9, lo que muestra que este modelo puede usarse con información temporal del COS escasa, información de la historia de uso de suelo y mediciones de la entrada de residuos vegetales aéreos y subterráneos en el suelo.The objective of this work was to simulate, by the RothC model, the changes in soil organic carbon (SOC) caused by changes of land use - from the traditional maize-squash (TMC) association to systems with castor bean (Ricinus communis): multilayer (MUL), alleys (CALL) and monoculture (HIG). SOC simulations were performed for 0-20 and 0-40 cm soil depths, for the period 1980-2040, considering the TMC system as the base line. SOC change rates estimated with RothC, for both soil depths, were 0.5-1.2, 0.4-0.8, 0.3-0.5 and 0.04-0.1 Mg ha-1 C per year in the HIG, MUL, CALL and TMC systems, respectively, and were consistent with those reported in the literature. RothC perfomance had 89% efficiency (EF) and R² = 0.9, which shows that this model can be used with scarce SOC temporal information, information on the history of land use, and with input measurements of aerial and underground plant residues in the soil