GF Marais, M Ghai, AS Marais, D Loubser and A Eksteen
Keywords: Abiotic stress tolerance - alien addition lines - intergeneric hybridization - gene transfer.
Abstract: An earlier study has shown that Thinopyrum distichum chromosomes 3J1 d, 4J1 d and 5J1 d are primarily responsible for its salt tolerance while 2J1 d and a group 7J chromosome may also contribute. Presently, RFLP polymorphisms and C-bands were used to develop disomic addition lines in triticale for each target chromosome barring 7J1 d. An initial attempt to find PCR-based markers for the critical chromosomes employed sequences of mapped wheat cDNA loci to derive primers for the amplification of Thinopyrum homoeoloci. This approach met with limited success and when the various addition stocks became available these were used to detect Thinopyrum-specific RAPDs that could be converted into SCAR markers. Using the SCAR markers, a range of Th. distichum – triticale secondary hybrids with different combinations of the critical chromosomes were selected and employed in a salt tolerance test. The results confirmed those of the earlier study and showed that certain chromosome combinations rather than single chromosomes were required for elevated levels of salt tolerance. Chromosomes 2J1 d plus 3J1 d appeared to be the only combination of two chromosomes at a time that produced a notable effect. Addition of either of the combinations 2J1 d, 3J1 d and 5J1 d or 3J1 d, 4J1 d and 5J1 d to triticale produced salt tolerance approaching that of the primary Th. distichum/ triticale amphiploid. Attempts to further characterize critical chromosome regions and to develop plant material with introgressed tolerance should therefore focus on the J1 d genome chromosomes 2, 3, 4 and 5.
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