Browsing Masters Degrees (Genetics) by Author "Barkhuizen, Johan Wilhelm"
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- ItemThe identification of RAPD markers for the Thinopyrum derived Lr19 translocation of wheat(Stellenbosch : Stellenbosch University, 1998) Barkhuizen, Johan Wilhelm; Marais, G. F.; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics & Institute of Plant Biotechnology.ENGLISH ABSTRACT: Ongoing attempts to introduce novel traits in wheat necessitate the development of detailed genetic maps to facilitate these processes. Thinopyrum ponticum derived leaf rust resistance (Lr19) has been successfully incorporated as a terminal translocation onto chromosome 7DL of wheat (Sharma & Knott, 1966). Following the induction of allosyndetic pairing between the translocated segment and homoeologous chromosome arms, a shortened translocation designated Lr19-149, was recovered (Marais 1992c). A number of near isogenic lines (NILs) have been developed using the two forms of Lr19 (Prins et al, 1997), as well as a set of 29 irradiation induced deletions of the original Lr19 translocation (Marais, 1992a). these proved very useful in the process of mapping the chromosome region. A poorly developed genetic map hamper attempts to study and modify the introgressed chromotin block. Polymorphic variation between a NIL and its recurrent parent can be detected on the molecular level making it possible to generate easily usable markers for mapping purposes. Since the Random Amplified Polymorphic DNA (RAPD) technique (Williams et al, 1990) requires very little knowledge of sequence information prior to its employment, and since its suitability has already been well demonstrated in a variety of species (Welsh and McClelland, 1990), it is a logical choice in the search for polymorphic markers. In this study four Lr19 RAPD markers have been identified, and mapped successfully and a further three repulsion phase markers for the corresponding wheat chromosome arm have been identified. The marker, Xus-OPK1580-7el, is located the closest to the Lr19 gene. This marker was used to confirm two putative Lr19-149 recombinants as Lr19 derivatives and suggested that a third recombinant has apparently lost the marker and must be the most useful (shortest) recombinant.