Establishment and characterisation of wheat genetic mapping populations

Doubled haploid populations from 5 carefully selected wheat (Triticum aesti vum L.) crosses were established in order to produce genetic maps. The char acterisation of the parental material included pedigree analyses to define the extent of the genetic relationships among the lines and to determine th e occurrence of alien chromosome segments that may contribute to segregatio n distortion. The characterisation of the parents also defined the range of grain quality traits that could be examined in the lines derived from each cross. Populations of up to 321 lines were produced using wide cross-media ted doubled haploid production from F-1 plants. Assessment of the lines for heterogeneity was carried out using readily identifiable phenotypic marker s and electrophoresis of seed storage proteins, with 2.3-11.6% of the lines being removed from further analysis. Segregation distortion was estimated in several populations where sufficient information from genetic markers wa s available. In a Sunco/Tasman doubled haploid population, heterogeneity wa s detected between the first 51 lines and the remainder of the mapping popu lation and this could be traced to F-1 plants that were produced from an ea rlier set of crosses. chi (2) tests on the mapping data available for the C ranbrook/Halberd, CD87/Katepwa, and Sunco/Tasman doubled haploid population s revealed segregation distortion at rates of 1.8%, 5.1%, and 12.5% respect ively. Whereas the wide-cross doubled haploid protocol does not appear resp onsible for the bulk of the non-Mendelian segregation observed, several pot ential sources were identified. In particular, clustering of distorted loci at specific chromosome regions appeared to be associated with the presence of alien introgressions in one of the parents. This was especially marked in the Sunco/Tasman population. Providing such distortions are recognised i n the models used, these populations provide powerful tools for extensive m apping studies to determine the genetic factors controlling grain quality t raits and other wheat characters of interest.