Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sunish K. Sehgal

Keywords

fusarium Head blight, nitrogen fixation (Diazotrophs), rye (Secale cereale), tan spot (Pyrenophora tritici-repentis ), wheat (Triticum aestivum), wild relatives

Abstract

Wheat is the third most staple food worldwide but current 1% annual improvement in the wheat production is insufficient to meet the growing demands in future. The narrow genetic base of wheat limits continuous improvement in wheat productivity and tolerance to biotic and abiotic stresses under changing climate. Wild ancestors and relatives of wheat hold a potential in widening the genetic pool of wheat and enhance its resilience to biotic and abiotic stresses. This study was focused towards characterizing the genetic diversity in wild relatives of wheat for disease resistance and efficient association with diazotrophs. In the first study, we evaluated a mini core set of Triticum turgidum subsp. (tetraploid wheat, AABB) for resistance to Fusarium head blight (FHB), leaf rust and tan spot. Three, six, and nine accessions showed resistance response to Fusarium head blight (FHB), leaf rust and tan spot respectively. These germplasm resources could be further exploited in wheat breeding. In the second study, in addition to tetraploid wheat, diploid and hexaploid germplasm of both wild and adapted species were evaluated for efficient association with diazotrophic bacteria by analyzing the N content. We observed significant differences for 15N content among different species, represented as average σ15N. Lower σ15N indicates a higher possibility of biologically fixed nitrogen (BNF). Wild accessions both in diploid (T. boeticum, AmAm, σ15N = 20.85) and tetraploid species (T. turgidum subsp. dicoccoides, AABB, σ15N = 16.44) showed significantly better associations with diazotrophs as compared to domesticated species (T. monococcum, AmAm, σ15N = 26.67) and modern hexaploid varieties (T. aestivum, AABBDD, σ15N =31.74). Our study shows that the wild species hold a promise in identification and characterization of efficient association with diazotrophic bacteria and this interaction can be recovered in modern cultivars of wheat to enhance the performance of wheat in marginal soils. In the final study, we analyzed the genetic diversity in the global collection (178 accessions) of rye using 4,037 high-quality SNPs and developed of a mini core set of 32 accessions of rye that represents more than 95 % of the allelic diversity (PIC = 0.25) of our collection (PIC = 0.26). Genome-wide association study (GWAS) was performed on 160 accessions (Secale cereale subsp. cereale) with 4,037 high-quality SNPs to identify genomic regions conferring tan spot resistance. Nearly 32%, 27%, 24%, and 17% accessions showed resistant, moderately resistant, moderately susceptible and susceptible reaction to Pyrenophora tritici-repentis race 5 (PTR race 5) respectively. Two QTLs conferring resistance to tan spot (PTR race 5) were identified (p= < 0.001) using mixed linear model (GAPIT) on chromosomes 5R and 2R. The QTLs QTs-sdsu-5R and QTs-sdsu-2R explained 13.11% and 11.62 % of the variation. In conclusion, wild relatives and ancestors of wheat hold a potential for wheat improvement especially for tolerance to abiotic and biotic factors.

Library of Congress Subject Headings

Wheat -- Variation.
Wheat -- Genetics.
Crop improvement.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

178

Publisher

South Dakota State University

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Rights Statement

In Copyright