| dc.description.abstract | Drought affects about 50% of wheat (Triticum aestivum L.) globally and is a major threat for sustainable wheat production. This dissertation discusses three studies carried out to dissect drought tolerance in hard red spring wheat (HRSW) in the northern United States of America (USA). The first study used a bi-parental mapping approach with a recombinant inbred line (RIL) population developed from a cross between a drought-tolerant cultivar, ‘Reeder’ (PI613586), and a drought-susceptible cultivar, ‘Albany.’ The RILs were evaluated in different locations in North Dakota (ND) over three years. Data were collected on plant height (PH), days to heading (DH), yield (YLD), test weight (TW), and thousand kernel weight (TKW). A high-density genetic map was constructed using Illumina’s Infinium 90K single nucleotide polymorphism (SNP) genotypic data. In the second study, the same RIL population was evaluated for PH, DH, YLD, TKW, number of tillers (TIL), number of spikes (SPK), canopy dry weight (CDW), and wilting score (WS) in the greenhouse rather than the field. The third study used association mapping (AM) approach with an association panel comprised of ≥350 genotypes which were evaluated for PH, DH, YLD, TW, and TKW in different locations in ND. The bi-parental mapping study identified a total of 38 QTL each in the field and the greenhouse experiment. Among those, a total of six and eight QTL respectively, were identified under drought conditions. A total of five and eight QTL respectively were identified for both control and drought conditions. Besides this, the bi-parental mapping study identified six QTL for Drought susceptibility index (DSI) in the greenhouse experiment. In contrast, AM study identified a total of 69 QTL where 16 QTL were identified under drought conditions and 50 QTL were identified under both drought and control conditions. Further, 12 genomic regions associated with drought tolerance were repeated across two and sometimes all three studies. Ten novel QTL on chromosomes 2D, 3D, 4A, 4D, 5B, 7A, and 7B were identified. The QTL identified exclusively under drought conditions, under both drought and normal conditions and for DSI could be helpful for developing drought-tolerant wheat cultivars through marker-assisted selection (MAS). | en_US |
