CLAUDIA VELEZ - Academia.edu (original) (raw)
Papers by CLAUDIA VELEZ
Theoretical and Applied Genetics, 2001
We evaluated cassava bacterial blight (CBB) infection in an pair-cross population of 150 individu... more We evaluated cassava bacterial blight (CBB) infection in an pair-cross population of 150 individuals derived from an intra-specific cross between two non-inbred cassava (Manihot esculenta Crantz) lines. The replicated trials were carried out in the field under high disease pressure over two consecutive crop cycles. Evaluations were conducted at 4 and 7 months after planting for the two cycles. Simple regression analysis and the nonparametric Kruskal-Wallis rank-sum test revealed that eight quantitative trait loci (QTLs) were involved in resistance. We detected changes in QTLs from crop cycle to crop cycle. The pathogen population (Xanthomonas axonopodis pv. manihotis) was also monitored over the period, using a restriction fragment length polymorphism probe and pathogenic tests. Changes in QTL detection over the 2 years could be correlated with changes in pathogen population structure. One QTL, located in linkage group D, was conserved over the two crop cycles, and in field to greenhouse evaluations. This study thus identified molecular markers useful for marker assisted-selection, a technique that can accelerate the long, multiple-season process of breeding for CBB resistance.
Revista Colombiana de Psiquiatría, 2012
Objetivo: Validar la versión KIDSCREEN-27 para padres en el Área Metropolitana de Medellín, Colom... more Objetivo: Validar la versión KIDSCREEN-27 para padres en el Área Metropolitana de Medellín, Colombia, incluyendo la subescala aceptación social (AS) del KIDSCREEN-52, pues esta permite evaluar el efecto del bullying en la calidad de vida (CV) del niño. Métodos: La población de estudio fueron padres de niños entre los 8 y 18 años, de Medellín y su Área Metropolitana. Se calculó una muestra de 1.150 padres, de acuerdo con las propiedades psicométricas por medir. Se realizó una validación de constructo, comparando las puntuaciones medias entre los grupos de baja y alta condición socioeconómica. También se efectuó la validez de contenido y la medición de fiabilidad, por medio de la consistencia interna y la estabilidad prueba-reprueba. Adicionalmente, se midió el acuerdo padre-hijo. Resultados: La consistencia interna fue adecuada (α de Cronbach 0,76-0,83). Los padres de niños con mejor condición socioeconómica tuvieron puntuaciones más altas en todas las dimensiones (p < 0,05). Las puntuaciones fueron más altas entre niños sanos. Las mujeres tuvieron menores puntuaciones que los hombres, y los niños, mayores que los adolescentes. Los CCI para la evaluación de la fiabilidad estuvieron por encima de 0,7 en todas las dimensiones, excepto *
Applied and …, 2004
Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and ... more Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and temporal dynamics of the cassava bacterial pathogen Xanthomonas axonopodis pv. manihotis. The population dynamics were addressed by comparing samples collected from 1995 to 1999 from six locations, spanning four different edaphoclimatic zones (ECZs). Forty-five different X. axonopodis pv. manihotis RFLP types or haplotypes were identified between 1995 and 1999. High genetic diversity of the X. axonopodis pv. manihotis strains was evident within most of the fields sampled. In all but one site, diversity decreased over time within fields. Haplotype frequencies significantly differed over the years in all but one location. Studies of the rate of change of X. axonopodis pv. manihotis populations during the cropping cycle in two sites showed significant changes in the haplotype frequencies but not composition. However, variations in pathotype composition were observed from one year to the next at a single site in ECZs 1 and 2 and new pathotypes were described after 1997 in these ECZs, thus revealing the dramatic change in the pathogen population structure of X. axonopodis pv. manihotis. Disease incidence was used to show the progress of cassava bacterial blight in Colombia during the 5-year period in different ecosystems. Low disease incidence values were correlated with low rainfall in 1997 in ECZ 1.
Phytopathology, 2000
ABSTRACT Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis, is a widesprea... more ABSTRACT Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis, is a widespread disease that affects cassava (Manihot esculenta). We collected 238 X. axonopodis pv. manihotis strains by intensively sampling single fields in four edaphoclimatic zones (ECZs) in Colombia. DNA polymorphism of different X. axonopodis pv. manihotis populations was assessed by restriction fragment length polymorphism (RFLP) analyses, repetitive sequence-based polymerase chain reaction (rep-PCR), and amplified fragment length polymorphism (AFLP) assays. Genetic diversity, phenetic relationships among strains, and the coefficient of genetic differentiation were determined. All strains were tested for aggressiveness on the susceptible cassava cv. MCOL 1522. Strains were also tested for virulence on cassava differentials adapted to the strains' respective ECZs. Our study showed that the Colombian X. axonopodis pv. manihotis population has a high degree of genetic diversity. The hierarchical analysis of diversity showed genotypic differentiation at all levels, among ECZs, among fields within ECZs, and among strains within fields planted to several cassava genotypes. New RFLP haplotypes were detected, leading to the characterization of a new pathotype. Dendrograms from AFLP were more robust than those from RFLP data. A close association between the strains' geographical origin and DNA polymorphism was obtained using RFLP and AFLP data. We suggest that the host played a role in causing pathogen differentiation.
Theoretical and Applied Genetics, 2001
We evaluated cassava bacterial blight (CBB) infection in an pair-cross population of 150 individu... more We evaluated cassava bacterial blight (CBB) infection in an pair-cross population of 150 individuals derived from an intra-specific cross between two non-inbred cassava (Manihot esculenta Crantz) lines. The replicated trials were carried out in the field under high disease pressure over two consecutive crop cycles. Evaluations were conducted at 4 and 7 months after planting for the two cycles. Simple regression analysis and the nonparametric Kruskal-Wallis rank-sum test revealed that eight quantitative trait loci (QTLs) were involved in resistance. We detected changes in QTLs from crop cycle to crop cycle. The pathogen population (Xanthomonas axonopodis pv. manihotis) was also monitored over the period, using a restriction fragment length polymorphism probe and pathogenic tests. Changes in QTL detection over the 2 years could be correlated with changes in pathogen population structure. One QTL, located in linkage group D, was conserved over the two crop cycles, and in field to greenhouse evaluations. This study thus identified molecular markers useful for marker assisted-selection, a technique that can accelerate the long, multiple-season process of breeding for CBB resistance.
Revista Colombiana de Psiquiatría, 2012
Objetivo: Validar la versión KIDSCREEN-27 para padres en el Área Metropolitana de Medellín, Colom... more Objetivo: Validar la versión KIDSCREEN-27 para padres en el Área Metropolitana de Medellín, Colombia, incluyendo la subescala aceptación social (AS) del KIDSCREEN-52, pues esta permite evaluar el efecto del bullying en la calidad de vida (CV) del niño. Métodos: La población de estudio fueron padres de niños entre los 8 y 18 años, de Medellín y su Área Metropolitana. Se calculó una muestra de 1.150 padres, de acuerdo con las propiedades psicométricas por medir. Se realizó una validación de constructo, comparando las puntuaciones medias entre los grupos de baja y alta condición socioeconómica. También se efectuó la validez de contenido y la medición de fiabilidad, por medio de la consistencia interna y la estabilidad prueba-reprueba. Adicionalmente, se midió el acuerdo padre-hijo. Resultados: La consistencia interna fue adecuada (α de Cronbach 0,76-0,83). Los padres de niños con mejor condición socioeconómica tuvieron puntuaciones más altas en todas las dimensiones (p < 0,05). Las puntuaciones fueron más altas entre niños sanos. Las mujeres tuvieron menores puntuaciones que los hombres, y los niños, mayores que los adolescentes. Los CCI para la evaluación de la fiabilidad estuvieron por encima de 0,7 en todas las dimensiones, excepto *
Applied and …, 2004
Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and ... more Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and temporal dynamics of the cassava bacterial pathogen Xanthomonas axonopodis pv. manihotis. The population dynamics were addressed by comparing samples collected from 1995 to 1999 from six locations, spanning four different edaphoclimatic zones (ECZs). Forty-five different X. axonopodis pv. manihotis RFLP types or haplotypes were identified between 1995 and 1999. High genetic diversity of the X. axonopodis pv. manihotis strains was evident within most of the fields sampled. In all but one site, diversity decreased over time within fields. Haplotype frequencies significantly differed over the years in all but one location. Studies of the rate of change of X. axonopodis pv. manihotis populations during the cropping cycle in two sites showed significant changes in the haplotype frequencies but not composition. However, variations in pathotype composition were observed from one year to the next at a single site in ECZs 1 and 2 and new pathotypes were described after 1997 in these ECZs, thus revealing the dramatic change in the pathogen population structure of X. axonopodis pv. manihotis. Disease incidence was used to show the progress of cassava bacterial blight in Colombia during the 5-year period in different ecosystems. Low disease incidence values were correlated with low rainfall in 1997 in ECZ 1.
Phytopathology, 2000
ABSTRACT Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis, is a widesprea... more ABSTRACT Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis, is a widespread disease that affects cassava (Manihot esculenta). We collected 238 X. axonopodis pv. manihotis strains by intensively sampling single fields in four edaphoclimatic zones (ECZs) in Colombia. DNA polymorphism of different X. axonopodis pv. manihotis populations was assessed by restriction fragment length polymorphism (RFLP) analyses, repetitive sequence-based polymerase chain reaction (rep-PCR), and amplified fragment length polymorphism (AFLP) assays. Genetic diversity, phenetic relationships among strains, and the coefficient of genetic differentiation were determined. All strains were tested for aggressiveness on the susceptible cassava cv. MCOL 1522. Strains were also tested for virulence on cassava differentials adapted to the strains' respective ECZs. Our study showed that the Colombian X. axonopodis pv. manihotis population has a high degree of genetic diversity. The hierarchical analysis of diversity showed genotypic differentiation at all levels, among ECZs, among fields within ECZs, and among strains within fields planted to several cassava genotypes. New RFLP haplotypes were detected, leading to the characterization of a new pathotype. Dendrograms from AFLP were more robust than those from RFLP data. A close association between the strains' geographical origin and DNA polymorphism was obtained using RFLP and AFLP data. We suggest that the host played a role in causing pathogen differentiation.