Author: Surya Laxmi Shrestha

Publisher:

Published: 2014

Total Pages:

ISBN-13:

Drought is a limiting factor for wheat (Triticum aestivum L.) production in the low precipitation regions of the Pacific Northwest (PNW). To improve wheat performance in drought, this study focused on three main objectives. Our first objective was to determine water use efficiency (WUE) in the PNW wheat lines through carbon isotope discrimination (CID) technique. Genotypic variation of CID was found in soft spring and hard winter wheat lines. Low CID or high WUE was found important for increasing yield of soft spring wheat lines in drought and semi-drought environments but not in other wheat types. The second objective of this study was to determine important physiological traits associated with yield. Fifteen spring wheat, 140 Alpowa/Express (AE) recombinant inbred lines (RILs) and 165 Hollis/Drysdale (HD) RILs, were evaluated in replicated field trials in two moisture environments, rainfed and irrigated, in different years. The wheat materials were screened for physiological (CT, CID, FLS: Flag leaf senescence), agronomic and phenological traits. The low canopy temperature (CT) was consistently associated with high yield in all wheat lines. The study found that CT was the main driver of wheat adaptation in drought in studied environmental conditions. Our third objective was to identify genomic regions associated with the studied traits through quantitative trait loci (QTL) mapping. In the AE population, yield and test weight QTL were identified on chromosome 1B in the irrigated environments but none of the QTL for physiological traits was found in this chromosomal region. The major QTL associated with yield and CT (at milking), which explained 15 and 22% of the phenotypic variation, were found on chromosome 3B in terminal drought environment. In the HD population, two QTL associated with yield were identified on chromosomes 2A and 4A in averaged rainfed environments in which yield QTL on chromosome 4A explained 35% of the phenotypic variation. These QTL for yield were associated with later FLS. Through the genetic dissection of yield into component traits, this study may help to incorporate quantitative traits into wheat drought breeding programs through marker-assisted selection.