Copper deficiency causes significant annual losses in grain yield due to poor grain set. Cereals such as wheat and barley are particularly susceptible to low copper soils whereas,crops such as rye and triticale are better able to grow and yield under such conditions of nutrient stress. The ability of rye and triticale, which carries a complete set of rye chromosomes, to tolerate low copper conditions has been attributed to a gene on rye chromosome 5R. Wheat-rye translocation lines have previously been produced carrying segments of the long arm of chromosome 5 of rye (5RL). Although these lines have expressed copper efficiency in University of Adelaide trials, until now they have been considered agronomically inferior and so have not been used as commercial cultivars. The physical size of rye segment of the 4BS.4BL-5RL translocation in a Chinese Spring background derived from the Cornell Wheat Selection 82a1-2-4-7 was measured using GISH (genomic in situ hybridization) and found to be 16% of the long arm. The size of this translocation was similar to GISH measurements of another 4BS.4BL-5RL translocation in Viking wheat background, although both these lines arose spontaneously and at different times. Molecular maps of both 4BS.4BL-5RL translocations in the two different wheat backgrounds were developed and used to screen for rare recombinants between wheat and rye in a background homozygous for the Sears' ph1b mutant. The maps revealed the approximate genetic location of the translocation breakpoint involved in these two 4BS.4BL-5RL translocations to be similar even though they are known to have arisen at different times and in different experimental populations. The similarity of these translocations suggests a unique property of the region at or near the translocation breakpoint that could be responsible for their similarity and spontaneous formation. After screening 703 critical seedlings for evidence of recombination between the 5RL segment and wheat homoeologues, no confirmed recombinants were identified. Lines containing the 4BS.4BL-5RL translocation were shown to yield equally as well as their recurrent parent under normal field conditions. In addition the presence of the 4BS.4BL-5RL had no adverse effects on a range of grain quality characteristics measured in these lines. A pot trial using lines derived from a cross between the CSHN translocation and the wheat cultivar Warigal (five backcrosses) revealed that they provided copper-efficiency even under the severest of deficiency conditions. While the results of this pot trial did not show the outstanding copper efficiency previously observed in these lines, the translocation did consistently out yield the recurrent parent under severe copper deficiency conditions. Finally, a reliable PCR marker was developed for the rapid identification of lines containing the distal portion of the 5RL chromosome. / Thesis (Ph.D.)--School of Agriculture and Wine, 2004.
| Identifer | oai:union.ndltd.org:ADTP/280214 |
| Date | January 2004 |
| Creators | Leach, Richard Charles |
| Source Sets | Australiasian Digital Theses Program |
| Language | en_US |
| Detected Language | English |
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