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Improving adaptation of staple crops in developing countries is important to ensure food security. In the West African country of Niger, the staple crop sorghum (Sorghum bicolor) is cultivated across diverse agroclimatic zones, but the genetic basis of local adaptation has not been described. The objectives of this study were to characterize the genomic diversity of sorghum from Niger and to identify genomic regions conferring local adaptation to agroclimatic zones and farmer preferences. We analyzed 516 Nigerien accessions for which local variety name, botanical race, and geographic origin were known. We discovered 144 299 single nucleotide polymorphisms (SNPs) using genotyping-by-sequencing (GBS). We performed discriminant analysis of principal components (DAPC), which identified six genetic groups, and performed a genome scan for loci with high discriminant loadings. The highest discriminant coefficients were on chromosome 9, near the putative ortholog of maize flowering time adaptation gene Vgt1. Next, we characterized differentiation among local varieties and used a genome scan of pairwise [F.sub.ST] values to identify SNPs associated with specific local varieties. Comparison of varieties named for light- versus dark-grain identified differentiation near Tannin1, the major gene responsible for grain tannins. These findings could facilitate genomics-assisted breeding of locally adapted and farmer-preferred sorghum varieties for Niger. Key words: sorghum, agroclimatic zones, genomics, local adaptation, genomics-enabled breeding, sub Saharan Africa. L'amelioration de cultures dans les pays en developpement est importante afin d'assurer securite alimentaire. En Afrique de l'Ouest, particulierement au Niger, le sorgho (Sorghum bicolor) est cultive dans differentes zones agroclimatiques. Cependant les bases genetiques de leur adaptation locale sont peu decrites. Cette etude a pour objectifs de caracteriser la structure genetique du sorgho au Niger et d'identifier les regions genomiques associees a l'adaptation locale aux zones agroclimatiques et aux preferences des agriculteurs. L'analyse par le genotypage par sequencage (GBS) de 516 accessions du Niger, dont le nom local, la race botanique et l'origine sont connus, nous a permis d'identifier 144 299 polymorphismes nucleotidiques (SNPs). La methode d'analyse discriminante des composantes principales a identifie six clusters genetiques. Le balayage genomique des coefficients de discrimination a montre des locus aux coefficients eleves au niveau du chromosome 9, colocalises avec le gene Vgt1 responsable de la variation de la date de floraison. Aussi, nous avons caracterise la differentiation des varietes locales. Le balayage genomique de [F.sub.ST] entre les varietes locales Mota (grains blancs) et Jenjari (grains sombres) a identifie des locus pres du Tannin1, le gene responsable des tanins. Ces resultats permettront de faciliter la selection assistee par la genomique de varietes de sorgho localement adaptees et preferees en Niger. Mots-cles: sorgho, zones agroclimatiques, genomique, adaptation locale, selection genomique, Afrique subsaharienne., Introduction Sorghum (Sorghum bicolor L. Moench) is a major staple crop that is adapted to multiple agroclimatic zones of the world (Smith and Frederiksen 2000). In smallholder production systems of [...]

Sorghum is one of the world's most important food, feed, and fiber crops as well as a potential feedstock for lignocellulosic bioenergy. Early-season planting extends sorghum's growing season and increases yield in temperate regions. However, sorghum's sensitivity to low soil temperatures adversely impacts seed germination. In this study, we evaluated the 242 accessions of the ICRISAT sorghum mini core collection for seed germination and seedling vigor at 12°C as a measure of cold tolerance. Genome-wide association analysis was performed with approximately 162177 single nucleotide polymorphism markers. Only one marker locus (Locus 7-2) was significantly associated with low-temperature germination and none with vigor. The linkage of Locus 7-2 to lowtemperature germination was supported by four lines of evidence: strong association in three independent experiments, co-localization with previously mapped cold tolerance quantitative trait loci (QTL) in sorghum, a candidate gene that increases cold tolerance and germination rate when its wheat homolog is overexpressed in tobacco, and its syntenic region in rice co-localized with two cold tolerance QTL in rice. This locus may be useful in developing tools for molecular breeding of sorghums with improved low-temperature germinability. Key words: sorghum, association mapping, SNP, early-season cold tolerance. Le sorgho est l'une des plus importantes cultures au monde, autant pour sa production de fibres que d'aliments pour les humains et les animaux, ainsi que pour son potentiel en tant que matiere premiere pour la production de bioenergie lignocellulosique. Un semis hatif permet de rallonger la saison de croissance et d'augmenter les rendements dans les regions temperees. Cependant, la sensibilite du sorgho aux basses temperatures du sol a des impacts negatifs sur la germination des graines. Dans cette etude, les auteurs ont evalue 242 accessions de la collection nucleaire minimale (<< mini core collection>>) de l'ICRISAT pour leur germination et la vigueur des plantules a 12 °C afin d'en mesurer la tolerance au froid. Une analyse d'association pangenomique a ete realisee au moyen d'environ 162177 marqueurs mononucleotidiques (SNP). Seul un marqueur (Locus 7-2) a montre une association significative avec la germination a basse temperature et aucun a la vigueur des plantules. L'association entre le Locus 7-2 et la germination a basse temperature etait supportee par quatre evidences : une forte association au sein de trois experiences independantes, une colocalisation avec des locus de caracteres quantitatifs (QTL) identifies anterieurement chez le sorgho, la presence d'un gene candidat qui accroit la tolerance au froid et le taux de germination lorsque l'orthologue de ce gene present chez le ble est surexprime chez le tabac, et le fait que la region correspondante chez le riz contient deux QTL pour la tolerance au froid. Ce locus pourrait s'averer utile en vue du developpement de sorghos dotes d'une meilleure germination a basse temperature a l'aide d'outils de selection moleculaires. [Traduit par la Redaction] Mots-cles : sorgho, cartographie par association pangenomique, SNP, basses temperatures en debut de saison., Introduction The response of plants to suboptimal temperatures is in part related to the center of origin of a given plant species. Plants with centers of origin in temperate regions [...]

Abstract: Sorghum has been improved by public and private breeding programs utilizing germplasm mostly from within the species Sorghum bicolor. Until recently, cross-incompatibilities have prevented hybridization of S. bicolor with [...]

Abstract: A comparison of approximately 4.5 kb of nucleotide sequence from the waxy locus (the granule-bound starch synthase I [GBSS I] locus) from a waxy line, BTxARGl, and a non-waxy [...]

Abstract: Sorghum bicolor (L.) Moench is an important grain and forage crop grown worldwide. We developed a simple sequence repeat (SSR) linkage map for sorghum using 352 publicly available SSR [...]

Abstract: Sorghum, Sorghum bicolor (L.) Moench, is the fifth most important cereal crop grown worldwide and the fourth in the United States. Greenbug, Schizaphis graminum (Rondani), is a major insect [...]

Abstract: We report here an analysis of the structure of genetic diversity in cultivated sorghums. A core collection of 210 landraces representative of race, latitude of origin, response to day [...]