Document Type

Dissertation - University Access Only

Award Date

2010

Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

Abstract

Traditional quantitative trait loci (QTL) mapping approaches typically use advanced generation material from bi-parental populations. One of the major limitations to such an approach is the time required to develop mapping populations such as recombinant inbred lines (RILs). As a result, conventional mapping populations are rarely part of a routine breeding program and thus hardly ever give rise to new cultivars. As a consequence; mapping and breeding efforts, introgression, marker validation, and marker-aided selection (MAS) are separate activities. Using early generation material from plant breeding families as a mapping population as such can help to (i) expedite the mapping process and (ii) develop a method which can perform all four of the above mentioned activities simultaneously. The objectives of this study therefore include (i) validating the family-based linkage and association approach in plants using Fusarium head blight (HIB) resistance in wheat as a model system, (ii) mapping resistance QTLs for FHB in SO3934 and Mult757 (iii) explore the prospect for simultaneous mapping, marker validation and marker-aided selection, and (iv) optimizing population size for the family-based approach using a simulated data set. The family-based method conventionally used in human and animals was validated in plant breeding families from the spring wheat breeding program at South Dakota State University. The well characterized QTL Fhb 1 conditioning resistance to FHB in wheat was used as a model system for validation. The QTL was mapped using both linkage (using variance component and pedigree-wide regression) and association-based approaches via the quantitative transmission disequilibrium test developed for extended family-pedigrees. Each approach successfully identified the known location for the QTL showing validity of the method. The validated method was used to map resistance QTL mapping in SD3934 and Mult757 wheat lines. The method identified a QTL in the 38S region of SO3934 and 'Sumai 3' derieved lines. The approach successfully identified a novel QTL on chromosome 78 in Mult757 (Pl 271127) with heritability of 27.25 to 31.7%. Besides empirical validation, computer simulations were carried out to calculate power for different sample sizes (number of families and number of individuals within each family), marker density, family type, and variance explained by the QTL. The average power to detect a QTL showed wide variation depending on population size (family size and number) composition of population (families developed from three- or four-way crosses), marker density, variance explained by the QTL, and levtel of significance. Selective genotyping was done by selecting 20% upper and bottom class of genotypes from the population used for validation study. The selective genotyping could map the QTL in the expected location without substantially reducing the likelihood of odds (LOD) score. Results of the experiments show usefulness of the family-based QTL mapping approaches for quick and efficient mapping via simultaneous mapping, marker selection, marker validation, and QTL introgression using plant breeding families.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance -- Genetic aspects

Wheat -- Genome mapping

Fusarium diseases of plants

Format

application/pdf

Number of Pages

184

Publisher

South Dakota State University

Download

Share

COinS