Das Projekt "Allel-Suche nach Resistenzgenen von Wildgersten mit Hilfe einer 'nested association' (NAM)-Kartierungspopulation" wird vom Umweltbundesamt gefördert und von Universität Halle-Wittenberg, Institut für Agrar- und Ernährungswissenschaften, Professur für Pflanzenzüchtung durchgeführt. The nested association mapping (NAM) design was recently implemented by Yu et al. (2008) and McMullen et al. (2009) in order to tap into the wealth of genetic diversity which is available for modern elite varieties. The NAM design applies a structured multi-family association mapping approach to localize quantitative trait loci (QTLs) regulating the expression of a Pillen, Ordon, Schweizer: Nested Association Mapping in Barley, 11.09.2009 Page 1 quantitative phenotype. The elegance of the method was recently demonstrated in a Science paper where the genetic architecture of the trait flowering time was successfully dissected in maize using a set of 5,000 NAM lines which were derived from 25 initial crosses (Buckler et al. 2009). During the course of the proposed project, we aim to develop a similar NAM population in barley, using wild barley accessions as donors for genetic variation. Our barley NAM population will consist of 1,500 BC1S4 individuals, derived from 25 families, each containing 60 individuals. The barley NAM population will originate from crosses between the elite barley cultivar 'Barke and 25 wild barley accessions (Hordeum vulgare ssp. spontaneum, Hsp), which were selected from Badr et al. (2000) and represent a large proportion of the genetic diversity present in Hsp. The NAM population will be utilized to identify and characterize exotic genes which participate as QTLs in the regulation of quantitative agronomic traits. For genetic characterization, the NAM population will be genotyped genome-wide with a set of 1,536 barley ILLUMINA SNPs (Rostoks et al. 2006). For phenotypic characterization, the NAM population will be evaluated in regard to pathogen resistance as well as to plant height, leaf and spike morphology. Subsequently, both data sets will be combined in order to localize QTLs which are associated with the phenotypic expression of the traits under study. For this goal, an association mapping study will be carried out as proposed in maize (Buckler et al 2009). Based on our previous findings (Pillen et al. 2003, von Korff et al 2005, 2006), we expect to identify a multitude of new wild barley alleles which may improve pathogen resistance in barley. Effective exotic alleles can, thus, be incorporated into elite breeding programs in order to improve and broaden the genetic base of our modern elite barley gene pool.