Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Long-Range Linkage Disequilibrium, Genetic Diversity Structure And Allele Mining In A Collection Of Durum Wheat Accessions

Marco Maccaferri¹ , Paola Mantovani¹ , Gerard van der Linden² , Roberto Tuberosa¹ , Maria C Sanguineti¹ , Silvia Giuliani¹

¹  Department of Agroenvironmental Science and Technology (DiSTA), University of Bologna, Viale Fanin 44, 40127 Bologna, Italy

²  Plant Research International B.V., Wageningen University and Research Centre, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands

At DiSTA (University of Bologna, Italy), a collection of 134 durum wheat accessions, representative of the major cultivated gene pools, has been assembled for allele mining and genetic association study purposes. A preliminary profiling with 70 SSRs has allowed for the identification of foundation genotypes accounting for a large portion of the genetic variation present among accessions. Results of both a distance-based and a model-based (Bayesian) cluster analysis evidenced the presence of a structured diversity: six to eight main distinct subgroups were identified. Population structure considerably inflated the overall long-range linkage disequilibrium (LD) values. However, after accounting for the population structure, it was possible to confirm the presence of LD, due to true linkage, in the majority of linked (< 20 cM) marker pairs. The collection is being evaluated for highly heritable traits, e.g. heading date, semolina yellow index, resistance to leaf rust, etc. The genetic variability in resistance genes (R-genes) and R-gene analogs (RGA) present within the durum collection has been investigated with molecular tools targeted to specific gene families, i.e. degenerate primers designed to match the conserved sequences of the Nucleotide-Binding-Site domain of R-genes (NBS profiling). Reliable banding patterns and an average polymorphism level similar to that observed with the standard AFLP technique were obtained. The implications of these findings as to the possibility of using association mapping for gene/QTL discovery and validation in durum wheat will be discussed. A larger set of accessions (up to 200) is being characterized molecularly and phenotypically in a collaborative EU Project (IDuWUE: http://137.204.42.130/iduwue/).