Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sunish K. Sehgal


Triticum aestivum, BLS, Spot Blotch, GWAS, gene mapping, quantitative trait locus, recombinant inbred lines, SNP markers


Spot blotch (SB), caused by Bipolaris sorokiniana (Sacc.) Shoem, and bacterial leaf streak (BLS), caused by Xanthomonas translucens pv. undulosa (Smith et al.), two important foliar diseases of wheat in the major production regions of the US and the world. Deployment of adequate host resistance against them depends on determining the resistance genes or quantitative trait loci (QTLs) responsible for the trait and identification of genetic markers linked to QTL that facilitate markers assisted breeding. We conducted two independent studies and characterized QTLs for BLS and SB resistance. In the first study, we constructed a genetic linkage map of 1,211 SNPs with 92 F5 recombinant inbred lines (RILs) developed from a cross between BLS resistant (SD52) and susceptible (SD1001) parental lines. Composite interval mapping (CIM) identified genomic regions (LOD≥2.3) on chromosomes 2B, 6D, 7A, and 7B linked to BLS resistance. The four QTLs for BLS resistance QBls.sdsu-2B-I (15.8%), QBls.sdsu-7A-I (6.1%) and QBls.sdsu-7B-I (10.9%), were derived from SD52 and aggregately explained 32.8% of the phenotypic variation. Also, a disease increasing QTL, QBls.sdsu-6D-I was identified from SD1001 accounting for 14.8% of the total variation. In the second study, we identified spot blotch resistance QTLs by evaluating 294 genotypes of hard winter wheat association mapping panel (HWWAMP) against Bipolaris sorokiniana (isolate SD40). Ranges of reactions were observed with ten highly resistant, 47 moderately resistant and 241 moderately susceptible to susceptible genotypes. Genome-wide association study (GWAS) using 15,590 highquality SNPs we identified six QTLs (p=

Library of Congress Subject Headings

Wheat -- Disease and pest resistance.
Wheat -- Genetics.
Leaf spots.
Gene mapping.


Includes bibliographical references (pages 97-133)



Number of Pages



South Dakota State University



Rights Statement

In Copyright