Use of Molecular Mapping Techniques for Adaptation to Rainfall Levels in Pacific Northwest Wheat.

Drought stress is a primary limitation of wheat production in the Pacific Northwest (PNW), as it is globally. Plants are typically stressed with low soil moisture and sometimes high temperature during flowering which is a critical period with high grain yield potential. To address this problem a molecular genetics approach was implemented using 188 Louise/Penawawa recombinant inbred lines (RIL).  Quantitative trait loci (QTL) were detected using a genetic linkage map constructed of 321 single sequence repeat and single nucleotide polymorphic markers. For drought tolerance, the population was tested in three moisture regimes in WA in 2009: Pullman rainfed, Lind rainfed and Lind irrigated conditions. The linkage map was made using Mapmaker version 3.0b and QTL were mapped with QTL Cartographer version 2.5 with a LOD threshold greater than 3.0 considered as a significant QTL. Parameters including yield, test weight and drought susceptibility index (DSI) were analyzed. One QTL for yield was found within a 42.3 cM region on chromosome 2DS and flanked by Xcfd036 and Xbarc168 in Pullman rainfed (LOD score 4.92) and Lind irrigated (LOD score 3.95) conditions. This QTL corresponded to the Ppd-D1 allele for photoperiod sensitivity as inherited from Louise. QTL for flowering date and maturity have also been identified in this same chromosomal region using the same mapping population. Two additional QTL for test weight, Xcfd036 (Pullman rainfed) and Xbarc168 (Lind rainfed), were found on 2DS. The Pullman rainfed QTL (LOD score 5.21) was localized to a 34.8 cM region flanked by Xcfd051 and Ppd-D1 whereas the Lind rainfed QTL (LOD score 3.46) was flanked by markers Ppd-D1 and Xcfd043. These QTL were inherited from Louise and Penawawa, respectively. Identification of these QTL allows further insight into developing high yielding wheat cultivars specifically adapted to different rainfall zones in the PNW.