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Taba, S.

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Taba, S.

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    Caracterización de accesiones de maíz por calidad de grano y tortilla
    (Sociedad Mexicana de Fitogenética, 2004) Mauricio Sánchez., R.A.; Figueroa, J. de D.; Taba, S.; Reyes Vega, M.; Rincón-Sánchez, F.; Mendoza Galván, A.
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    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
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    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.
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    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.
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    Annual research report 2000: Maize genetic resources
    (CIMMYT, 2000) Taba, S.; Remier, H.; Kirubi, D.; Diaz, J.
    Maize genetic resources program has three pillars, namely germplasm accessions management, in-situ biodiversity conservation, and prebreeding. Germplasm accessions management includes specific cooperative project ofregeneration of the Latin American maize landrace accessions, and evaluation and curatorial of the CIMMYT bank accessions. In-situ-biodiversity conservation entails the collecting and evaluation, and enhancement of specific landraces that are grown by the farmers in the context with their growing environment and cultural heritage in Mexico. Prebreeding is to develop and improve CIMMYT gene pools with incorporation of appropriate germplasm sources that are adapted in tropical, subtropical, and highland environment. For in-situ biodiversity conservation we evaluated new collections of Mexican race Zapalote Chico with our Mexican collaborators. Evaluations of additional Tuxpefio race and Brazilian races of Cateto and its subraces were conducted for development of core subsets. Formation and evaluation of breeding crosses of elite accessions were initiated or advanced in GEM type germplasm enhancement. In prebreeding topcross evaluations of a few tropical early pools, progeny formation of S 1 or S2, and development of donor sources were made mostly for yellow gene pools. Bank management and accessions introduction through the collaborative project with Latin American countries resulted in the total number of accessions that amounted to 20,863 as of September 2000. We made the seed shipment from Bank in the seed packets of 5,248 during the year.
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    Maize Genetic Resources: annual report 2002
    (CIMMYT, 2002) Taba, S.; Krakowsky, M.; Kirubi, D.
    We have completed the first cycle of RRS in the tropical and subtropical yellow gene pools. The best S2 lines were increased for seed distribution. In pool 25 and 26, to determine combining ability of the S2 lines selected by RRS, 10 best S2 were chosen to make the testcrosses with two inbred lines and the opposite pool. A half of the highland gene pools were planted and advanced to S1. Enhancement of donor germplasm sources and their testcross evaluations were performed for tropical and subtropical yellow flint and dent pools. Yellow flint and dent donor sources were developed for tropical gene pools: 17, 18, 25, and 26. Latin American germplasm regeneration project has continued, receiving the regenerated accessions from Mexico, Venezuela, Ecuador, and Peru. CIMMYT regeneration was focused on Chile, Argentine, and Brazilian accessions. Accessions evaluation was conducted with the accessions from Argentine. The regeneration and germplasm evaluation was slightly less than what was desired. Seed distribution was met as requested. The number of seed packets prepared for distribution was less as compared to those in the previous years.
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    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.
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    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.
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    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.
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    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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