Date of Award

12-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Engineering and Earth Sciences

Advisor

Ksenija Gasic

Committee Member

Gregory Reighard

Committee Member

Douglas Bielenberg

Committee Member

Feng Chen

Abstract

Genetic control and location of QTLs associated with phytochemical compounds in peach were evaluated using bi-parental mapping and genome wide association (GWAS). The bi-parental mapping was conducted in an F2 population (ZC2) derived from cross between ‘Zin Dai’ x ‘Crimson Lady’. GWAS was performed on an association panel representing modern peach cultivars available and/or produced for the U.S. market. Antioxidant capacity and phenolic compound accumulation (total phenolics, flavonoids and anthocyanins) were evaluated for two years on all materials. The ZC2 progeny were genotyped using IPSC 9K peach SNP array v1., and the association panel was genotyped using genotyping-by-sequencing. The genetic linkage map, constructed with 908 SNP markers distributed among eight linkage groups, covers a genetic distance of ~ 336 cM, with an average marker density of 1.07 cM/marker. Total of 6 QTLs associated with phytochemical traits were identified on 5 linkage groups (LGs). Two major QTLs were observed on LG 6 and 8. qPC.ZC-6.1 was associated with all phytochemical compounds, while qPC.ZC-8.1 exhibited association only with total phenolics and anthocyanin content. GWAS, performed on a dataset of 18,085 SNPs and all phytochemical compounds, revealed a significant association (P < 0.05) for 129 SNPs covering the entire genome. A Majority of SNPs (121) were associated with anthocyanin accumulation and spread across all LGs, while 8 SNPs on LG7 were associated with both antioxidant capacity and flavonoid content. Overlap was observed between SNPs associated with anthocyanin accumulation, detected via GWAS, and major QTL for phytochemical compounds on LG6, identified using the bi-parental population.

Validation of functional alleles associated with accumulation of phytochemical compounds will enable development of a simple DNA test(s) to predict phenotype response to accumulation of these compounds in young seedlings without the need for fruit evaluation.

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