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A genome-wide association study (GWAS) was undertaken to unravel marker-trait associations (MTAs) between SNP markers and phenotypic traits. It involved a subset of 421 cacao accessions from the large and diverse collection conserved ex situ at the International Cocoa Genebank Trinidad. A Mixed Linear Model (MLM) in TASSEL was used for the GWAS and followed by confirmatory analyses using GAPIT FarmCPU. An average linkage disequilibrium (r2) of 0.10 at 5.2 Mb was found across several chromosomes. Seventeen significant (P ≤ 8.17 × 10-5 (-log10 (p) = 4.088)) MTAs of interest, including six that pertained to yield-related traits, were identified using TASSEL MLM. The latter accounted for 5 to 17% of the phenotypic variation expressed. The highly significant association (P ≤ 8.17 × 10-5) between seed length to width ratio and TcSNP 733 on chromosome 5 was verified with FarmCPU (P ≤ 1.12 × 10-8). Fourteen MTAs were common to both the TASSEL and FarmCPU models at P ≤ 0.003. The most significant yield-related MTAs involved seed number and seed length on chromosome 7 (P ≤ 1.15 × 10-14 and P ≤ 6.75 × 10-05, respectively) and seed number on chromosome 1 (P ≤ 2.38 × 10-05), based on the TASSEL MLM. It was noteworthy that seed length, seed length to width ratio and seed number were associated with markers at different loci, indicating their polygenic nature. Approximately 40 candidate genes that encode embryo and seed development, protein synthesis, carbohydrate transport and lipid biosynthesis and transport were identified in the flanking regions of the significantly associated SNPs and in linkage disequilibrium with them. A significant association of fruit surface anthocyanin intensity co-localised with MYB-related protein 308 on chromosome 4. Testing of a genomic selection approach revealed good predictive value (genomic estimated breeding values (GEBV)) for economic traits such as seed number (GEBV = 0.611), seed length (0.6199), seed width (0.5435), seed length to width ratio (0.5503), seed/cotyledon mass (0.6014) and ovule number (0.6325). The findings of this study could facilitate genomic selection and marker-assisted breeding of cacao thereby expediting improvement in the yield potential of cacao planting material.

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RESUMEN A través de la historia de un chamán maya yucateco (h-men), este artículo analiza los cambios y las continuidades en el chamanismo yucateco y, más específicamente, en una de sus funciones principales: tsak, "curar". Los resultados presentados aquí son parte de un trabajo de campo de 40 años, de 1976 a 2016. El autor vive en una comunidad del centro de Yucatán (Tabi, Sotuta) y ha realizado varias investigaciones sobre el chamanismo yucateco en comunidades de los estados de Yucatán, Campeche y Quintana Roo. Juan Cob, h-men de Yaxcabá, no es solo un informante sino también vecino, amigo del autor con el cual realizó varias películas

ABSTRACT Through the history of a Yucatecan Mayan shaman (h-men), this article analyzes the changes and continuities in Yucatecan shamanism and, more specifically, in one of its main functions: tsak, healing. The results presented here are part of fieldwork carried out over 40 years, from 1976 to 2016. The author lives in a community in central Yucatán (Tabi, Sotuta) and has carried out a number of research studies on Yucatecan shamanism in communities in the Mexican states of Yucatán, Campeche and Quintana Roo. Juan Cob, h-men of Yaxcabá, is not only an informant but also the author's friend and neighbor, with whom he has created a number of films

Assuntos

RESUMO

Through the history of a Yucatecan Mayan shaman (h-men), this article analyzes the changes and continuities in Yucatecan shamanism and, more specifically, in one of its main functions: tsak, healing. The results presented here are part of fieldwork carried out over 40 years, from 1976 to 2016. The author lives in a community in central Yucatán (Tabi, Sotuta) and has carried out a number of research studies on Yucatecan shamanism in communities in the Mexican states of Yucatán, Campeche and Quintana Roo. Juan Cob, h-men of Yaxcabá, is not only an informant but also the author's friend and neighbor, with whom he has created a number of films.

A través de la historia de un chamán maya yucateco (h-men), este artículo analiza los cambios y las continuidades en el chamanismo yucateco y, más específicamente, en una de sus funciones principales: tsak, "curar". Los resultados presentados aquí son parte de un trabajo de campo de 40 años, de 1976 a 2016. El autor vive en una comunidad del centro de Yucatán (Tabi, Sotuta) y ha realizado varias investigaciones sobre el chamanismo yucateco en comunidades de los estados de Yucatán, Campeche y Quintana Roo. Juan Cob, h-men de Yaxcabá, no es solo un informante sino también vecino, amigo del autor con el cual realizó varias películas.

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MAIN CONCLUSION: Microsatellite and single nucleotide polymorphism markers that could be used in marker assisted breeding of cacao were identified for number of filled seeds, black pod resistance and witches' broom disease resistance. An association mapping approach was employed to identify markers for seed number and resistance to black pod and witches' broom disease (WBD) in cacao (Theobroma cacao L.). Ninety-five microsatellites (SSRs) and 775 single nucleotide polymorphisms (SNPs) were assessed on 483 unique trees in the International Cocoa Genebank Trinidad (ICGT). Linkage disequilibrium (LD) and association mapping studies were conducted to identify markers to tag the phenotypic traits. Decay of LD occurred over an average 9.3 cM for chromosomes 1-9 and 2.5 cM for chromosome 10. Marker/trait associations were generally identified based on general linear models (GLMs) that incorporated principal components from molecular information on relatedness factor. Seven markers (mTcCIR 8, 66, 126, 212; TcSNP368, 697, 1370) on chromosomes 1 and 9 were identified for number of filled seeds (NSEED). A single marker was found for black pod resistance (mTcCIR280) on chromosome 3, whereas six markers on chromosomes 4, 5, 6, 8, and 10 were detected for WBD (mTcCIR91, 183; TcSNP375, 720, 1230 and 1374). It is expected that this association mapping study in cacao would contribute to the knowledge of the genetic determinism of cocoa traits and that the markers identified herein would prove useful in marker assisted breeding of cacao.

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Ecuador's economic history has been closely linked to Theobroma cacao L cultivation, and specifically to the native fine flavour Nacional cocoa variety. The original Nacional cocoa trees are presently in danger of extinction due to foreign germplasm introductions. In a previous work, a few non-introgressed Nacional types were identified as potential founders of the modern Ecuadorian cocoa population, but so far their origin could not be formally identified. In order to determine the putative centre of origin of Nacional and trace its domestication history, we used 80 simple sequence repeat (SSR) markers to analyse the relationships between these potential Nacional founders and 169 wild and cultivated cocoa accessions from South and Central America. The highest genetic similarity was observed between the Nacional pool and some wild genotypes from the southern Amazonian region of Ecuador, sampled along the Yacuambi, Nangaritza and Zamora rivers in Zamora Chinchipe province. This result was confirmed by a parentage analysis. Based on our results and on data about pre-Columbian civilization and Spanish colonization history of Ecuador, we determined, for the first time, the possible centre of origin and migration events of the Nacional variety from the Amazonian area until its arrival in the coastal provinces. As large unexplored forest areas still exist in the southern part of the Ecuadorian Amazonian region, our findings could provide clues as to where precious new genetic resources could be collected, and subsequently used to improve the flavour and disease resistance of modern Ecuadorian cocoa varieties.

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