Agronomy and Horticulture Department


Date of this Version

Spring 4-21-2010


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of the Requirements For the Degree of Doctor of Philosophy, Major: Agronomy (Plant Breeding and Genetics), Under the Supervision of Professor P. Stephen Baenziger. Lincoln, Nebraska: May, 2010
Copyright (c) 2010 Neway C. Mengistu


Grain yield and yield-related traits are the most important economic factors for bread wheat (Triticum aestivum L.) improvement. Grain yield (GYLD) and yield-related quantitative trait loci (QTLs) were previously identified by using a population of recombinant inbred chromosome lines (RICLs) developed from cultivar ‘Cheyenne’ (CNN) and its substitution line CNN(WI3A), where the 3A chromosome of cultivar ‘Wichita’ (WI) was substituted for the CNN chromosome 3A. The objectives of this study were to identify and validate GYLD and yield-related QTLs previously identified in CNN(RICLs-3A) studies by using the mirror population WI(RICLs-3A), where chromosome 3A of CNN and WI were now recombined in the WI background. A population of 90 F1-derived doubled haploid lines derived from WI x WI(CNN3A) was used to evaluate GYLD, 1000-kernel weight (TKW), kernels per spike (KPS), kernels per square meter (KPSM), spikes per square meter (SPSM), grain volume weight (GVW), anthesis date (AD), and plant height (PHT). The agronomic traits data were collected from replicated trials grown in six Nebraska environments from 2008 to 2009. Twelve QTLs associated with variation for GYLD, TKW, KPS, SPSM, GVW, AD, and PHT were detected. The phenotypic variance explained by these QTLs ranged from 12% for SPSM to 53% for GVWT. Most of the QTLs were co-localized in a cluster or closely linked into two regions of chromosome 3A. The major grain yield QTL (QGyld.neb.3A.1) detected in the combined analysis explained 19% of the phenotypic variance and the substitution of a CNN allele for a WI allele decreased grain yield by 87 kg ha-1. Using a different genetic background, this study detected most of the GYLD and yield-related QTLs reported in previous RICLs-3A mapping studies on chromosome 3A of winter wheat evaluated in Nebraska. The identified QTLs or genomic regions associated with GYLD and yield-related traits will be a useful tool for future marker assisted breeding in improving the yield potential of bread wheat. Additional work such as fine-mapping and cloning the QTLs for grain yield and yield-related traits will facilitate utilization of these traits in breeding programs.