EVALUACIÓN DE UN MÉTODO NUMÉRICO DE MEDICIÓN DEL DIÁMETRO DE LA FIBRA DE ALPACA

This study presents the statistical evaluation of a digital image alpaca fibre diameter measurement method, Digital Image Fibre Diameter Analysis (DIFDA). This method developed in the International Potato Center (CIP) requires an evaluation of the fibre sample digital image process, prepared in slides covers and taked from a scanner of negatives and films. DIFDA presents two options for fibre diameter measurement process: Digital image complete and sections of the digital image. The results of the fibre sample are mean fibre diameter, standard deviation and coefficient of variability. The objective was to test and compare the mean fibre diameter values obtained by DIFDA with the values from two conventionals methods: Projection Microscope and OFDA (Optical Fibre Diameter Analysis). In adition, DIFDA’s process options were evaluated. Two hundred six alpaca fibre samples from Pacomarca Farm, Puno, were evaluated. The mean fibre diameter samples values, measured by commercials methods, Projection Microscope and OFDA, were, 21.64 ± 3.58 and 21.74 ± 4.0, respectively. The mean fibre diameter reported for DIFDA was 21.74 ± 3.03. No statistical differences between the methods were detected. The Pearson’s correlation coefficient for DIFDA and Projection Microscope and for DIFDA and OFDA was 0.87 and 0.84, respectively. The process of DIFDA could be done in the complete digital image option, or using three or more sections for the dimention of 1000 x 1000 pixels, or five or more sections for the dimention of 500 x 500 pixels. The conclutions were that the DIFDA’s results showed no statistical significative differences between neither the Projection Microscope’s nor the OFDA’s results. Consequently, this measurement method would be used satisfactorily in breeding programs that requires continuos fibre measurement.El presente estudio evalúa el método de medición de diámetro de la fibra de alpaca mediante el procesamiento de imagen digital, Digital Image Fibre Diameter Analisis (DIFDA), desarrollado en el Centro Internacional de la Papa, y lo compara con los valores obtenidos mediante dos métodos de medición convencionales: Lanámetro (Microscopio de Proyección) y OFDA (Optical Fibre Diameter Analysis). El DIFDA requiere de una evaluación del proceso de imágenes digitales obtenidas mediante un escáner de transparencias y negativos de una muestra de fibra de alpaca preparada en porta slides. Este método presenta una opción de procesamiento de imagen digital completa o otra de secciones dentro de la imagen digital, donde los resultados se expresan en promedio, desviación estándar y coeficiente de variación. Un total de de 206 muestras de fibra de alpacas del fundo Pacomarca, Puno, fueron evaluadas. Los valores promedio de diámetro de las fibras fueron de 21.74 ± 3.03, 21.64 ± 3.58 y 21.74 ± 4.01 según los métodos DIFDA, Lanámetro y OFDA, respectivamente; sin haber diferencia significativa entre promedios. El coeficiente de correlación de Pearson entre DIFDA con el lánametro fue de 0.87 y con OFDA fue de 0.84. La medición del diámetro puede realizarse procesando la imagen digital completa, a partir de tres secciones de 1000 x 1000 píxeles, o desde cinco secciones de 500 x 500 píxeles. Se concluye que no existe diferencia significativa entre los resultados de DIFDA y de los métodos Lanámetro y OFDA, por lo que su uso puede ser de utilidad en programas de mejoramiento animal que requieren medición continua del diámetro de fibras

Development of a Panel of Genome-Wide Ancestry Informative Markers to Study Admixture Throughout the Americas

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R2>0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

An integrated agro-ecosystem and livelihood systems approach for the poor and vulnerable in dry areas

More than 400 million people in the developing world depend on dryland agriculture for their livelihoods. Dryland agriculture involves a complex combination of productive components: staple crops, vegetables, livestock, trees and fish interacting principally with rangeland, cultivated areas and watercourses. Managing risk and enhancing productivity through diversification and sustainable intensification is critical to securing and improving rural livelihoods. The main biophysical constraints are natural resource limitations and degradation, particularly water scarcity and encroaching desertification. Social and economic limitations, such as poor access to markets and inputs, weak governance and lack of information about alternative production technologies also limit the options available to farmers. Past efforts to address these constraints by focusing on individual components have either not been successful or are now facing a declining rate of impact, indicating the need for new integrated approaches to research for development of dryland systems. This article outlines the characteristics of such an approach, integrating agro-ecosystem and livelihoods approaches and presents a range of empirical examples of its application in dryland contexts. The authors draw attention to new insights about the design of research required to accelerate impact by integrating across disciplines and scales

Development of a panel of genome-wide ancestry informative markers to study admixture throughout the Americas

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R2>0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

Development of a panel of genome-wide ancestry informative markers to study admixture throughout the Americas.

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R² > 0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

Performance of nested subsets of AIMs.

<p>Performance of nested subsets of AIMs.</p