An SSR-based genetic linkage map of the model grass Brachypodium distachyon

Introduction The majority of the domesticated grass crops are cool-season species belonging to one of the four core pooid tribes: the Triticeae, Aveneae, Bromeae, and Poeae (Davis and Soreng 1993). [...]
The grass species Brachypodium distachyon (hereafter, Brachypodium) has been adopted as a model system for grasses. Here, we describe the development of a genetic linkage map of Brachypodium. The genetic linkage map was developed with an [F.sub.2] population from a cross between the diploid Brachypodium lines Bd3-1 and Bd21. The map was populated with polymorphic simple sequence repeat (SSR) markers from Brachypodium expressed sequence tag (EST) and bacterial artificial chromosome (BAC) end sequences and conserved orthologous sequence (COS) markers from other grass species. The map is 1386 cM in length and consists of 139 marker loci distributed across 20 linkage groups. Five of the linkage groups exceed 100 cM in length, with the largest being 231 cM long. Assessment of colinearity between the Brachypodium linkage map and the rice genome sequence revealed significant regions of macrosynteny between the two genomes, as well as rearrangements similar to those reported in other grass comparative structural genomics studies. The Brachypodium genetic linkage map described here will serve as a new tool to pursue a range of molecular genetic analyses and other applications in this new model plant system. Key words: Brachypodium, genetic analysis, molecular marker, SSR, linkage map, purple false brome. Le Brachypodium distachyon (Brachypodium) a ete adopte comme espece modele chez les graminees. Dans ce travail, les auteurs decrivent le developpement d'une carte genetique chez le Brachypodium. La carte a ete deeveloppeeea partir d'une population [F.sub.2] issue d'un croisement entre les ligneees diploldes Bd3-1 et Bd21 du Brachypodium. La carte est composee de marqueurs microsatellites (SSR) provenant de l'analyse d'eetiquettes de sequences exprimees (EST) et de sequences terminales de clones BAC (chromosomes bacteeriens artificiels) du Brachypodium ainsi que de marqueurs de sequences orthologues conservees (COS) provenant d'autres graminees. La carte mesure 1386 cM et compte 139 marqueurs distribues sur 20 groupes de liaison. Cinq des groupes de liaison mesurent plus de 100 cM, le plus long totalisant 231 cM. Une etude de la co-linearite entre la carte genetique du Brachypodium et la sequence genomique du riz a revele d'importantes regions de macrosynteenie entre les deux genomes, ainsi que des rearrangements semblables a ceux rapportees lors d'etudes similaires en genomique structurale chez d'autres graminees. La carte genetique du Brachypodium decrite dans ce travail servira de nouvel outil pour une gamme d'analyses moleculaires ainsi que d'autres applications chez ce nouveau modele chez les plantes. Mots-cles: Brachypodium, analyse genetique, marqueur moleeculaire, SSR, carte genetique, brachypode a deux epis. [Traduit par la Redaction]