Person:
Taba, S.

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Taba
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Taba, S.

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Now showing 1 - 10 of 11
  • Reporte final del trabajo de monitoreo y recolección de poblaciones de teocintle para su conservación in-situ y ex-situ por el Banco de Germoplasma de Maíz del CIMMYT
    (CIMMYT, 2011) Taba, S.
    El status de conservación del Teocintle en México fue reportado por The Crop Diversity Trust en la estrategia de conservación de recursos genéticos de maíz en el año de 2007 en Roma, Italia. Los objetivos actuales son el cumplimiento de algunas recomendac
    Publication
  • Genetic diversity and population structure of native maize populations in Latin America and the Caribbean
    (Public Library of Science, 2017) Bedoya-Salazar, C.A.; Dreisigacker, S.; Hearne, S.; Franco, J.; Mir, C.; Prasanna, B.M.; Taba, S.; Charcosset, A.; Warburton, M.
    This study describes the genetic diversity and population structure of 194 native maize populations from 23 countries of Latin America and the Caribbean. The germplasm, representing 131 distinct landraces, was genetically characterized as population bulks using 28 SSR markers. Three main groups of maize germplasm were identified. The first, the Mexico and Southern Andes group, highlights the Pre-Columbian and modern exchange of germplasm between North and South America. The second group, Mesoamerica lowland, supports the hypothesis that two separate human migration events could have contributed to Caribbean maize germplasm. The third, the Andean group, displayed early introduction of maize into the Andes, with little mixing since then, other than a regional interchange zone active in the past. Events and activities in the pre- and post-Columbian Americas including the development and expansion of pre-Columbian cultures and the arrival of Europeans to the Americas are discussed in relation to the history of maize migration from its point of domestication in Mesoamerica to South America and the Caribbean through sea and land routes.
    Publication
  • Background on the development of the: global strategy for the Ex situ conservation and utilization of maize germplasm
    (Global Crop Diversity Trust, 2007) Goodman, M.; Taba, S.
    The genetic resources of maize constitute an immeasurable treasure for humankind. Conservation of maize germplasm and knowledge about its variation and uses provide (i) resources for agricultural improvement to reduce hunger and poverty and (ii) a solid knowledge base for future generations of researchers and technological users. The variability among maize landraces exceeds that for any other crop. The collection and study of the accessions of the races of maize are unprecedented in man's agricultural heritage; their maintenance and regeneration has been remarkable, and their widespread and open availability to research workers has been unique (Taba, 2005). Nonetheless, problems remain: 1. Integration of maize germplasm resources and maize breeding is challenging; historically, efforts have been inconsistent. 2. Most racial studies of maize have been New-World-oriented. 3. Regeneration of some eco-specific accessions has been difficult. 4. Distribution of individual seed requests via national germplasm banks as generally been ineffective due to resource and/or policy issues. 5. Phytosanitary restrictions are a major bottleneck in distributing germplasm samples. 6. Teosinte populations are endangered and have scattered (and less than complete) representation in the major international germplasm banks. 7. Documentation of the materials held in national collections is inconsistent, and sometimes poor, and is held in multiple databases that are not necessarily well maintained or easily accessible. 8. Tripsacum populations are part of the secondary gene pool of maize genetic resources, and some are endangered; some populations should be monitored and conserved. 9. Developing a worldwide strategy for preservation, documentation, distribution, and utilization of maize genetic resources will require attention to these and other, generally less difficult, problems.
    Publication
  • Efecto del tamaño del gránulo de almidón de maíz en sus propiedades térmicas y de pastificado
    (Sociedad Mexicana de Fitogenética, 2007) Narvaez-Gonzalez, E.D.; Figueroa, J. de D.; Taba, S.; Castaño Tostado, E.; Martinez Peniche, R.A.
    El grano de maiz (Zea mays L.) esta compuesto principalmente por almidon, cuyo tamaño varia entre razas. El conocimiento del proceso de gelatinizacion del almidon provee informacion importante acerca de la funcionalidad, requerimientos energeticos y uso final de este cereal. El objetivo de este estudio fue investigar las relaciones entre el tamaño del granulo de almidon y sus propiedades termicas y de pastificado en 71 razas puras de maiz provenientes Mexico, El Caribe, Centro y Sudamerica. Las imagenes de los granulos se obtuvieron con un microscopio electronico de barrido ambiental, de muestras de endospermo duro y endospermo suave. Las temperaturas y entalpia de gelatinizacion fueron obtenidas por medio del calorimetro de barrido diferencial. Las propiedades de pastificado se midieron con un analizador rapido de viscosidad. Se determinaron los contenidos de humedad, proteina, lipidos y amilosa aparente, asi como la dureza del grano. Los granulos pequeños gelatinizan lentamente y a altas temperaturas y entalpia. Los granos suaves mostraron gránulos mas grandes en el endospermo suave y pequeños en el endospermo duro; lo contrario se observo en granos duros. La dureza presentó correlaciones altamente significativas con el tiempo y la temperatura para alcanzar el pico de viscosidad. El tamaño del granulo de almidon correlaciono positivamente con los contenidos de humedad y amilosa aparente, pero negativamente con el contenido de proteína en el endospermo suave de las muestras.
    Publication
  • Genetic characterization of a core set of a tropical maize race Tuxpeño for further use in maize improvement
    (Public Library of Science, 2012) Weiwei Wen; Franco, J.; Chavez Tovar, V.H.; Jianbing Yan; Taba, S.
    The tropical maize race Tuxpeño is a well-known race of Mexican dent germplasm which has greatly contributed to the development of tropical and subtropical maize gene pools. In order to investigate how it could be exploited in future maize improvement, a panel of maize germplasm accessions was assembled and characterized using genome-wide Single Nucleotide Polymorphism (SNP) markers. This panel included 321 core accessions of Tuxpeño race from the International Maize and Wheat Improvement Center (CIMMYT) germplasm bank collection, 94 CIMMYT maize lines (CMLs) and 54 U.S. Germplasm Enhancement of Maize (GEM) lines. The panel also included other diverse sources of reference germplasm: 14 U.S. maize landrace accessions, 4 temperate inbred lines from the U.S. and China, and 11 CIMMYT populations (a total of 498 entries with 795 plants). Clustering analyses (CA) based on Modified Rogers Distance (MRD) clearly partitioned all 498 entries into their corresponding groups. No sub clusters were observed within the Tuxpeño core set. Various breeding strategies for using the Tuxpeño core set, based on grouping of the studied germplasm and genetic distance among them, were discussed. In order to facilitate sampling diversity within the Tuxpeño core, a minicore subset of 64 Tuxpeño accessions (20% of its usual size) representing the diversity of the core set was developed, using an approach combining phenotypic and molecular data. Untapped diversity represents further use of the Tuxpeño landrace for maize improvement through the core and/or minicore subset available to the maize community.
    Publication
  • Comparative SNP and haplotype analysis reveals a higher genetic diversity and rapider LD decay in tropical than temperate germplasm in maize
    (Public Library of Science, 2011) Yanli Lu; Shah, T.; Zhuanfang Hao; Taba, S.; Shihuang Zhang; Shibin Gao; Jian Liu; Moju Cao; Jing Wang; A. Bhanu Prakash; Tingzhao Rong; Yunbi Xu
    Understanding of genetic diversity and linkage disequilibrium (LD) decay in diverse maize germplasm is fundamentally important for maize improvement. A total of 287 tropical and 160 temperate inbred lines were genotyped with 1943 single nucleotide polymorphism (SNP) markers of high quality and compared for genetic diversity and LD decay using the SNPs and their haplotypes developed from genic and intergenic regions. Intronic SNPs revealed a substantial higher variation than exonic SNPs. The big window size haplotypes (3-SNP slide-window covering 2160 kb on average) revealed much higher genetic diversity than the 10 kb-window and gene-window haplotypes. The polymorphic information content values revealed by the haplotypes (0.436?0.566) were generally much higher than individual SNPs (0.247?0.259). Cluster analysis classified the 447 maize lines into two major groups, corresponding to temperate and tropical types. The level of genetic diversity and subpopulation structure were associated with the germplasm origin and post-domestication selection. Compared to temperate lines, the tropical lines had a much higher level of genetic diversity with no significant subpopulation structure identified. Significant variation in LD decay distance (2?100 kb) was found across the genome, chromosomal regions and germplasm groups. The average of LD decay distance (10?100 kb) in the temperate germplasm was two to ten times larger than that in the tropical germplasm (5?10 kb). In conclusion, tropical maize not only host high genetic diversity that can be exploited for future plant breeding, but also show rapid LD decay that provides more opportunity for selection.
    Publication
  • The Gametophyte-1 locus and reproductive isolation among Zea mays subspecies
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2006) Kermicle, J.L.; Taba, S.; Evans, M.
    Fourteen paired populations of annual teosinte and an associated maize landrace were characterized for allelic composition of the potential crossing barrier locus ga1. The four populations of subspecies parviglumis teosinte carried predominately ga1 or Ga1-m, both of which are receptive to ga1 pollen. The sole population of subspecies huehuetenangensis was polymorphic for Ga1-m and for Ga1-s, which is unreceptive to ga1 pollen. Ga1-s predominated among the six weedy populations of subspecies mexicana whereas the three ruderal/weedy populations of this subspecies contained ga1 or Ga1-m. This distribution suggests a role for Ga1-s enabling weedy populations to grow in intimate association with maize. However, the predominant allele in sympatric maize landraces proved to be Ga1-m, which regularly fertilized Ga1-s in controlled crosses. The Ga1-s pistil barrier thus would seem unable to prevent teosinte from being fertilized by sympatric maize. Nevertheless, Ga1-s pollen fertilized Ga1-s Ga1-s plants somewhat mor effectively than Ga1-m when both were present. This preference may be strengthened by modifier gene differences between teosinte and maize, thereby providing partial reproductive isolation between the two.
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  • Evaluation of Zapalote Chico accessions for conservation and enhancement
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2006) Taba, S.; Diaz, J.; Aragon Cuevas, F.; Rincón-Sánchez, F.; Hernandez, J.M.; Krakowsky, M.
    Conserving traditional maize (Zea mays L.) landraces grown by farmers in Latin America can con- tribute to food security. Core subsets of such landraces that represents that diversity can be used for their en- hancement. One such enhancement effort was conducted on a total of 81 accessions drawn from the CIMMYT maize collection of the race Zapalote Chico and newer accessions collected in 1999 from Istmo de Tehuantepec, Oaxaca, Mexico, where the race Zapalote Chico is pre- dominantly grown. These accessions were evaluated at four locations in the Mexican states of Morelos, Guerrero, and Oaxaca for agronomic and morphological traits to as- sess the intraracial diversity for conservation and en- hancement. Eleven agronomic and morphological traits were measured and used for a multivariate cluster analy- sis. The cluster analysis produced four non-overlapping clusters with 63 accessions, indicating the intraracial di- versity of the Zapalote Chico. The analysis also formed two other clusters with four races, including Tepecintle and Olotillo, which have been introduced to the region of Istmo de Tehuantepec. Using a selection index that ac- counts for grain yield, grain quality, and standability, and an agronomic performance rating, a breeder core subset (the best 20%) was chosen to represent phenotypic diver- sity among the clusters. In the core subset, fifteen acces- sions comprise the core subset of the race Zapalote Chico and three accessions comprise the core subset for the other races. These core subset accessions, which repre- sent the diversity of the regional landraces of maize, can be enhanced through introgression of improved lines or populations for yield potential, drought resistance, and ear rot resistance, while maintaining the desirable grain quality traits of the original races.
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  • Aspectos microestructurales y posibles usos del maíz de acuerdo con su origen geográfico
    (Sociedad Mexicana de Fitogenética, 2007) Narvaez-Gonzalez, E.D.; Figueroa, J. de D.; Taba, S.
    La mayoría de los estudios microesructurales del maíz se han orientado a la industria de los almidones y pocos se han relacionado con alimentos o calidad de tortilla. Se estudió la relación entre la microestructura del grano y las propiedades funcionales de razas de maíz de América Latina, y su posible uso de acuerdo con la zona geográfica. Se analizaron aspectos microestructurales, como grado de compactación de los cuerpos celulares del endoespermo, tamaño y morfología del gránulo de almidón, de 71 razas de maíz, El usoo final del grano estuvo relacionado con su microestructura. Granos con altos grados de compactación, con gránulos de almidón pequeño (<12 µm), de forma hexagonal y rodeados de una densa matriz proteica, predominaron en razas aptas para elaborar palomitas de maíz. A medida que el grado de compactación y el grosor del pericarpio (75 µm) disminuyeron, aumentó el tamaño del gránulo de almidón y el grano correspondió a razas aptas para botanas, harinas, "tortillas", "pozoles" y "atoles". Las razas apropiadas para elaborar "pozoles" y "atoles" presentaron gránulos de almidón esféricos y menor grosor de pericarpio (32 µm). Las razas apropiadas para elaborar torillas y harinas niztamalizadas presentan ambas clasas de morfología debido a la proporción casi igual de endospermo suave y duro en el grano. Las razas de México y Sudamérica tuvieron una amplia variación en los usos estudioados, mientras que las de Centroamérica y El Caribe mostraron ser apropiadas solamente para tortillas y botanas.
    Publication
  • Sampling strategies for conserving maize diversity when forming core subsets using genetic markers
    (Crop Science Society of America (CSSA), 2006) Franco, J.; Crossa, J.; Warburton, M.; Taba, S.
    Core subsets can be formed on the basis of molecular markers and different sampling strategies. This research used genetic markers on three maize data sets for studying 24 stratified sampling strategies to investigate which strategy conserved the most diversity in the core subset as compared with the original sample. The strategies were formed by combining three factors: (i) two clustering methods (UPGMA and Ward), based on (ii) two initial genetic distance measures, and using (iii) six allocation criteria [two based on the size of the cluster and four based on maximizing distances in the core (the D method) used with four diversity indices]. The objectives were (i) to study the influence of these factors and their interaction on the diversity of the core subsets and (ii) to compare the 24 stratified sampling strategies with the M strategy implemented in the MSTRAT algorithm. Success of each strategy was measured on the basis of maximizing genetic distances (Modified Roger and Cavalli‐Sforza and Edwards distances) and genetic diversity indices (Shannon index, proportion of heterozygous loci, and number of effective alleles) in each core. Twenty independent stratified random samples were obtained for each strategy using a sampling intensity of 20% of the collection. For the three data sets, the UPGMA with D allocation methods produced core subsets with significantly more diversity than the other methods and were better than the M strategy for maximizing genetic distance. For most of the diversity indices, the M strategy outperformed the D method.
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