Genome Wide Association Mapping for Abiotic and Biotic Stresses in Barley (Hordeum vulgare L.) Using Diverse Arrays of Doubled Haploids Derived From Intercrossing Exotic and Adapted Germplasm
The following dissertation consists of six sections: a general introduction, three manuscripts, a general conclusion, and an overall bibliography. The three manuscripts report on: (1) identifying genetic interactions in diverse germplasm developed during introgression of a major gene conferring resistance to stem rust (Puccinia graminis f. sp. tritici), (2) mapping genetic resistance for two of the most important diseases affecting barley (stem rust and stripe rust (Puccinia striiformis f. sp. hordei)) and (3) genetic analysis of components of winter-hardiness: low temperature tolerance (LTT), vernalization (VRN) sensitivity, and short-day photoperiod (PPD) sensitivity. The first manuscript reports introgression of stem rust resistance conferred by the rpg4/Rpg5 complex into diverse germplasm in order to prepare for the eventual arrival of race TTKSK. This race is a particular threat because more than 95% of cultivated barley accessions tested are susceptible. A range of disease reactions – from susceptible to resistant – in germplasm with the rpg4/Rpg5 introgression revealed that alleles at this complex locus are necessary but not sufficient for seedling resistance. Alleles at quantitative trait loci (QTLs) were identified that, together with rpg4/Rpg, conferred resistance. The second manuscript reports development of germplasm, with potentially different end-use qualities, that has adult plant resistance to stripe and stem rust. We validated QTLs for stripe rust resistance reported in previous studies, identified QTLs for adult plant resistance to stem rust under environmental conditions where rpg4/Rpg5 is not effective, and developed lines with resistance to both diseases. The third manuscript describes the association mapping of LTT and VRN sensitivity in a germplasm array developed from crosses designed to develop winter-hardy germplasm for use in the development of two-row winter and facultative malting varieties. QTLs, and corresponding candidate genes previously reported in the literature were principal sources of variation. The germplasm developed described in these three manuscripts is available to the breeding and research communities.