Document Type

Thesis - Open Access

Award Date

2008

Degree Name

Master of Science (MS)

Department / School

Agronomy

Abstract

Much effort has been invested in identification of molecular markers linked to quantitative trait loci (QTL) that confer Fusarium Head Blight (FHB) resistance, though levels significantly higher than those of 'Sumai-3' remain elusive. Additional resistance QTLs may exist which typically are overshadowed by partial resistance of susceptible parents used in development of mapping populations. The objectives of this research were: (a) Evaluate the mapping population for incidence, severity and disease index values (b) Genotype the whole population with both marker types (DArT and SSR) and (c) Create a linkage map to examine the association between resistance phenotypes and markers in an attempt to identify undiscovered resistance QTLs. Our population was created by crossing Sumai-3 with the very susceptible 'YI 193-6' (a Tibetan accession with unknown pedigree). An F2:6, recombinant inbred mapping population was developed. Out of the 65 polymorphic SSR markers and 352 DArT markers, we were able to map only 357 markers (305 DArT and 52 SSR) in 25 linage groups spanning approximately 3186cM. Phenotypic evaluation of FHB was conducted in four experiments (two in greenhouse and two in field conditions). Spray inoculations were done in both field and green settings. Based on visual scoring of disease incidence and severity, disease index scores were calculated and used to correlate with genotypic data. We found three QTLs on chromosome arms 3BS, 6BL and 2DS which explained 26.1, 10.7 and 18.9% of phenotypic variation for disease index respectively. These QTLs were also significantly associated with reduced Fusarium Damaged Kernels (FOK) and explained a larger percentage (28.0, 11.0 and 23.0%) of phenotypic variation on 3BS, 6BL and 2DS, respectively. Though two QTLs on chromosome arms 3BS and 6BL have been previously identified in Sumai-3, the 2DS QTL is not common among resistant parents. In this study the 2DS resistance QTL was contributed by the susceptible parent, Y 1193-6. This and some previously reported studies show there is a resistance QTL on chromosome arm 2DS. This study demonstrates that Sumai-3 can not be fully relied upon as a source of FHB resistance because it appears to lack a resistance QTL on chromosome 2DS.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance -- Genetic aspects

Wheat -- Genome mapping

Fusarium diseases of plants

Fungal diseases of plants

Format

application/pdf

Number of Pages

83

Publisher

South Dakota State University

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