Molecular Genetic Analysis of Domestication Traits in Emmer Wheat. I: Map Construction and QTL Analysis using an F2Pupulation

Emmer wheat (Triticum turgidum ssp. dicoccum) was a principal crop in the development and spread of Neolithic agriculture in the Old World. It represents the primitive situation in the domestication of AABB tetraploid wheat. To understand the genetic modifications underlying the early stage of tetraploid wheat domestication, QTL analysis was carried out using 144 F2 plants derived from a cross between the domesticated emmer wheat and the wild emmer wheat (T. turgidum ssp. dicoccoides). To our knowledge, this is the first report of molecular linkage map and QTL analysis of the domestication-related characters in emmer wheat. The linkage map with a total length of 2849.8 cM was constructed using 227 microsatellite (SSR) markers. Chromosomal location and effect of QTLs were estimated for ten domestication-related traits including whole plant and spike characteristics. Seventeen QTLs were detected on chromosomes 1B, 2A, 2B, 3A, 3B, 4A, 5B, and 7B. Two regions on chromosomes 2A and 3B have a large effect on rachis fragility. The estimated locations of these QTLs corresponded to those of the Br genes identified in the previous studies on a more adapted durum wheat (T. turgidum ssp. turgidum conv. durum). Our results indicate that selection and conversion of at least two Br loci (on chromosomes 2A and 3B) occurred during the domestication of emmer wheat prior to appearance of free-threshing wheat (e.g. durum). The map positions of nine QTLs for the traits related to seed production overlapped in two regions on chromosomes 2A and 5B. The result suggests that these chromosomal regions played an important role in increasing seed production during the domestication of emmer wheat.