El desarrollo del mapa genético de yuca ha facilitado las investigaciones en la búsqueda de genes asociados con resistencias a plagas que disminuyen producción y calidad. Las herramientas moleculares como los marcadores facilitan la identificación de los genes que dominan la resistencia a plagas como el caso del ácaro verde (AVY) Mononychellus tanajoa en yuca (Manihot esculenta). Inicialmente se identificaron los individuos de poblaciones retrocruces (BC1) progenie de las cuatro familias denominadas CW. De estos BC1 se seleccionaron individuos resistentes y susceptibles teniendo en cuenta la escala de daño reportada por el programa de Entomología del Centro Internacional de Agricultura Tropical. Se evaluaron 500 cebadores microsatélites mediante análisis de grupos segregantes (BSA), cinco de ellos expresaron polimorfismo y mostraron diferencias significativas entre los parentales, los grupos contrastantes y tres cebadores SSRY 11 SSRY 346 y NS 1099. Al realizar los análisis estadísticos correspondientes se encontró que los cebadores NS 1099 y NS 346 presentaron asociación entre estos y los individuos de las familias CW 67 CW 66 y CW 67 respectivamente. Las familias CW67 Y CW66 presentaron la mejor asociación con los marcadores y éstos presentaron mayor asociación con la característica de resistencia al daño causado por M. tanajoa en la población segregante (cebador NS1099 familias CW66 0.56 CW67 0.61 y NS346 familia CW67 0.61). Con base en estos resultados se puede sugerir la utilización de microsatélites en análisis posteriores en otras poblaciones para lograr la identificación de algunas regiones cromosómicas que confieren la resistencia al ácaro verde de la yuca.

The development of the cassava genetic map has promoted research such as the finding of genes associated with the resistance of pests that diminish the production and quality of the crop. Molecular tools, such as markers can facilitate the identification of the genes that dominate resistance to pests this is the specific case of the presence of resistance to the green mite Mononychellus tanajoa (CGM) in cassava (Manihot esculenta). Initially, at International Center for Tropical Agriculture CIAT, individuals populations of backcrosses (BC1), lineage of four denominated families CW, were identified. These BC1 were identified and categorized according to 1-5 scale of damage reported by the Entomology Program at International Center for Tropical Agriculture. Resistant and susceptible individuals were identified. A total of 500 microsatellite markers were evaluated using the bulk segregant analysis (BSA). Five of them expressed polymorphism and showed significant differences between parental and contrast groups and three markers, namely, SSRY 11, SSRY 346 and, NS 1099. Statistical analysis revealed that markers NS 1099 and NS 346 displayed the highest association between resistance and the individuals of families CW 67, CW 66 and CW 67, respectively. On the basis of these results we can recommend the use of microsatellite for further analysis in other populations in order to achieve the of some chromosomal regions conferring resistance to green mite cassava.

O método de melhoramento atualmente usado para o programa de mandioca é longo porque, na etapa inicial, dá-se maior prioridade ao rendimento e a qualidade das raízes vem depois. Para encurtar este método, ambos o rendimento e a qualidade das raízes devem ser selecionadas simultaneamente, começando no viveiro das novas mudas. Neste estudo realizado na Colômbia, uma população de viveiro constituída de oito famílias de mandioca e 1885 novas mudas desenvolvidas a partir de parentais adaptados a três grandes regiões agro-ecológicas diferentes foram avaliadas em termos de características de rendimento da cultura. A porcentagem do conteúdo de matéria seca (MS) e o índice de colheita produziram um ranking semelhante ao dos parentais. O rendimento do tubérculo, peso e número de raízes mostraram potencial de rendimento crescente através do melhoramento convencional. Recomenda-se o uso de um índice de seleção combinado incluindo o rendimento de raízes frescas, a porcentagem de MS, o peso e o número de raízes por planta; esses dois últimos com maior peso.

The cassava breeding scheme currently used is long, because initial stages concentrate mainly on improving yield, with root quality selection following later. To shorten the scheme, yield and root quality should be selected simultaneously, starting at the seedling nursery. In this study, a nursery comprising of eight cassava families and 1885 seedlings developed from parents adapted to three major agro-ecologies, were evaluated for yield related traits in Colombia. Percentage dry matter content (DMC) and harvest index produced similar ranking of the parents. Tuber yield, weight, and number showed potential of increasing yield through conventional breeding. A selection index including fresh root yield, percentage DMC, root weight and roots per plant, with heavier weights being assigned to root weight and roots per plant, should be used.

La población S1 de la variedad tailandesa de yuca MTAi8 (AM320), la cual presenta patrones de segregación definidos para el contenido de carotenos totales (Beta-caroteno), se sometió a un análisis de agrupamiento segregante (BSA = Bulk Segregant Analysis) empleando 700 marcadores moleculares tipo microsatélites o SSR. Se generaron 25 grupos de ligamiento identificando 3 QTL mayores asociados con una región del genoma de yuca con el contenido de carotenos totales. Tres marcadores SSR explicaron el 37.2% (NS109), 32% (rSSRY251) y 27.7% (rSSRY313) de la varianza fenotipica total, situados en el grupo de ligamiento D fuertemente asociados con el contenido de carotenos totales en la familia AM320 S1, se estableció una fuerte correlación positiva entre color de pulpa de raíz y contenido de carotenos totales (r=0.81), y negativa entre carotenos totales y materia seca (r= -0.31). Los tres posibles QTL presentaron efecto positivo y de carácter aditivo para el contenido de carotenos totales, pueden ser la oportunidad para implementar selección asistida por marcadores para carotenos totales en yuca.

The S1 population of the Thai variety MTAi8 (AM320), which shows patterns of segregation defined by the content of total carotenes (beta-carotene), underwent an analysis of segregating bulk (BSA = Bulk segregating Analysis) using 700 molecular markers type microsatellites or SSR. There were generated 25 tying groups and identifying 3 major QTLs associated with a region of the genome of cassava with the content of total carotenes. Three markers SSR; explained the 37.2% (NS109), 32% (rSSRY251) and 27.7% (rSSRY313) of the total phenotypic variance, placed in the Group D strongly tying, associated with the content of total carotenes in the family AM320 S1, which established a strong positive correlation between color and content root pulp carotenes total (r = 0.81), and between negative and carotenes total dry matter (r = -0.31). The three possible QTLs showed positive and additive effect for the content of totals carotenes and could be an opportunity to implement assisted selection markers for total carotenes in cassava.