Molecular Breeding for Salt Tolerance, Pre-Harvest Sprouting Resistance and Disease Resistance Using Synthetic Hexaploid Wheats, Genetic Transformation, and Associated Molecular Markers

Abstract

For the preharvest sprouting (PHS) studies, 2 accessions of Aegilops tauschii were chosen, based on their levels of dormancy, and crossed with durum wheat to produce synthetic hexaploids Syn36 and Syn37 following colchicine treatment. Elite, Australian PHS susceptible bread wheat cultivars, Janz, Yitpi, Mitre and Lang were crossed with the resistant Syn 36 and moderately-resistant Syn37. The RIL populations were grown under field conditions in Victoria, Australia. The PHS experiments identified RILs with phenotypic values outside the range of the parental genotypes, which can be differentiated statistically and repeatedly when exposed to more than 7 days of high humidity and rain in the artificial rain chamber. In the Syn36 × Janz BC1F5RIL an association between SI and VI was observed. The association between GI14 and VI was stronger than between GI14 and SI indicating that different mechanisms may contribute to PHS resistance. Molecular characterization indicated that genomic regions on chromosomes 1D, 3D, 5D and 6D, mostly derived from A. tauschii, influenced PHS. The source of resistance on chromosome 6D was Janz. The salt tolerance studies identified 7 SH's that expressed significantly lower Na+ values in the 3rd leaf compared to Kharchia and Westonia. One SH expressed 57% less Na+ than Kharchia. In a related experiment, a total of 26 transformation vectors for expression of candidate genes targeted to extended tolerance for drought were created and 529 independent transgenic wheat plants generated.