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Genotypic and phenotypic analysis of a Nepali spring wheat (Triticum aestivum L.) population

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dc.contributor.advisor Navabi, Alireza
dc.contributor.advisor Raizada, Manish
dc.contributor.author Khadka, Kamal
dc.date.accessioned 2020-05-22T20:19:08Z
dc.date.available 2020-05-22T20:19:08Z
dc.date.copyright 2020-05
dc.date.created 2020-05-06
dc.date.issued 2020-05-22
dc.identifier.uri http://hdl.handle.net/10214/17960
dc.description.abstract Nepal has been completely dependent on introduced wheat (Triticum aestivum L.) germplasm for variety development despite having >500 landraces in the national genebank. No Nepali wheat genetic resources were involved in the development of any of the 43 varieties released in Nepal for commercial cultivation. Nepal’s capacity to genotype and phenotype its wheat germplasm, in order to utilize it for breeding, is in its infancy due to a lack of resources. To assist breeding efforts for Nepal, here, I hypothesized that: (1) Nepali spring wheat germplasm is genetically and phenotypically diverse; (2) that the important physio-morphological traits have a genetic basis; and (3) that promising accessions for future targeted breeding can be identified using such genotyping and phenotyping. I assembled the Nepali Wheat Diversity Panel (NWDP) consisting of 318 spring wheat accessions including landraces, CIMMYT lines and released varieties. The NWDP was phenotyped in four different field experiments (2 each in Nepal and Canada) and also under controlled conditions. Analysis of 95K high density GBS markers showed greater genetic diversity in the Nepali landrace group compared to modern germplasm. Unexpectedly, the population structure analysis revealed four, rather than 3 subpopulations as was originally expected based on breeding history, with significant admixture within each subpopulation. A genome-wide association study (GWAS) revealed 15 significant marker-trait associations (MTAs) for 6 agro-morphological traits. Targeted genotyping was conducted to assess the accessions for allelic variation at dwarfing loci (Rht) and a photoperiod insensitivity locus (Ppd), both targets of modern selection. Promising accessions for future breeding were identified that possessed dwarfing alleles but conversely also seedling vigour related traits with potential to promote early season drought tolerance. The NWDP also showed significant variation for NDVI, SPAD values and shoot waxiness. I suggest that the Nepali landraces should be further characterized to identify the “authentic” landraces while the genotypic information available should be further utilized in genomic selection. The data suggest that shoot waxiness may be confounding spectral reflectance measurements especially when a germplasm population is extremely diverse. In conclusion, it is hoped that this thesis will better inform and accelerate wheat breeding for Nepal. en_US
dc.description.sponsorship Canadian International Food Security Research Fund (CIFSRF), jointly funded by the International Development Research Centre (IDRC, Ottawa) and Global Affairs Canada, and partial funding from SeCan, the Agricultural Adaptation Council and Grain Farmers of Ontario en_US
dc.language.iso en en_US
dc.subject Nepali wheat diversity panel en_US
dc.subject Waxiness en_US
dc.subject NDVI en_US
dc.subject Population structure en_US
dc.subject GWAS en_US
dc.title Genotypic and phenotypic analysis of a Nepali spring wheat (Triticum aestivum L.) population en_US
dc.type Thesis en_US
dc.degree.programme Plant Agriculture en_US
dc.degree.name Doctor of Philosophy en_US
dc.degree.department Department of Plant Agriculture en_US
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