Genetic diversity of wheat wild relative, Aegilops tauschii, for wheat improvement

• Main Author: Singh, Narinder
• Language: en_US
• Published: Kansas State University 2017
• Subjects: Genomic; Population structure; Physical mapping; Hessian fly; Genebank curation; Germplasm collection
• Online Access: http://hdl.handle.net/2097/38259

Doctor of Philosophy === Genetics Interdepartmental Program === Jesse A. Poland === Wheat is perhaps the most important component in human diet introduced since the conception of modern agriculture, which provides about 20% of the daily protein and calorie intake to billions of people. Adaptable to wide range of climates, wheat is grown worldwide, lending it the potential to mitigate the imminent risk of food security for future population of 9.5 billion people. For developing improved crop varieties in the future, genetic diversity is a key factor in plant breeding. Constraints in wheat evolution and artificial selection practices have resulted in erosion of this ingredient in elite germplasm. However, wheat wild relatives, such as Ae. tauschii, D-genome donor of wheat, are a storehouse for unexploited genetic diversity that can be used for improving wheat for disease and insect resistance, yield, quality, and tolerance to abiotic stresses. More than 1700 genebanks around the world hold over 7 million accessions of these wild relatives. These genebanks are expensive to maintain, therefore, efficient curation is necessary. We developed and implemented a protocol to identify duplicate accessions using genomic tools. Implementing this approach with three genebanks, we identified over 50% duplicated accessions across genebanks. There are over a million Triticeae accessions held collectively, and it is likely as more number of genebanks are tested, there will be decreasing number of unique accessions. Selecting and utilizing the wild genetic diversity is no easy task. Historically, breeders and geneticists have chosen the accessions primarily based on associated phenotypic data. Unless focusing on a targeted trait, this practice is imperfect in capturing the genetic diversity with some other limitations, such as confounding phenotypic data with the testing environment. Utilizing next-generation sequencing methods, we selected a MiniCore consisting of only 40 accessions out of 574 capturing more than 95% of the allelic diversity. This MiniCore will facilitate the use of genetic diversity present in Ae. tauschii for wheat improvement including resistance to leaf rust, stem rust, Hessian fly, and tolerance to abiotic stresses. Hessian fly is an important insect pest of wheat worldwide. Out of 34 known resistance genes, only six have been mapped on the D sub-genome. With swift HF evolution, we need to rapidly map and deploy the resistance genes. Some of the undefeated HF resistance genes, such as H26 and H32, were introgressed from Ae. tauschii. In this study, we mapped three previously known genes, and a new gene from Ae. tauschii accession KU2147. Genes were mapped on chromosomes 6B, 3D, and 6D. Further, identification and cloning of resistance genes will enhance our understanding about its function and mode of action. In conclusion, wild wheat relatives are genetically diverse species, and utilizing the novel genetic diversity in Ae. tauschii will be fruitful for wheat improvement in the wake of climate change to ensure future food security to expected 2 billion newcomers by 2050.