Degree

Doctor of Philosophy (PhD)

Department

School of Plant, Environmental and Soil Sciences

Document Type

Dissertation

Abstract

Sweetpotato [Ipomoea batatas (L.) Lam] is a globally important food, feed, and industrial crop, yet its improvement is constrained by a complex hexaploid genome, clonal propagation, and susceptibility to multiple diseases. In Louisiana, production is threatened primarily by Fusarium oxysporum f. sp. batatas (Fusarium wilt) and Ceratocystis fimbriata (Black rot). Furthermore, the in vitro propagation methods essential for disease-free planting material and germplasm conservation can introduce epigenetic instability that undermines clonal fidelity. This dissertation integrates genome-wide association studies (GWAS), genotype by environment interaction (GEI) and DNA methylation profiling to dissect resistance mechanisms and assess epigenetic stability in Louisiana sweetpotato breeding germplasm.

A half-sib breeding population derived from 15 elite parents was genotyped with ~3,000 high-quality DArTag SNP markers. GWAS for Fusarium wilt resistance identified significant loci on chromosome 3 harboring significant QTLs related to glycine-rich proteins pathways central to plant immunity. Parallel GWAS for Black rot resistance revealed a single SNP on chromosome 5 with distinct associations with gene regulating pathogen and stress signaling.  Moreover, the analysis of GEI highlighted the influence of environmental factors on genotype performance, for Black rot resistance across locations and years. These findings provide valuable insights for improving black rot resistance in sweetpotato and support continued efforts to refine molecular markers and enhance the stability of resistant lines across diverse environments.

This dissertation also examined epigenetic dynamics as potential factor influencing sweetpotato performance beyond genetic variation. The exploration of epigenetic regulation via bisulfite sequencing and methylation analysis was conducted under two contexts: (i) tissue culture propagation (meristematic vs. nodal systems across Murasaki-29, Bellevue, and Bonita half-sib progenies) and (ii) drought stress. Importantly, tissue culture shows higher clonal uniformity as compared to drought (environmental stressor) in long-term culture.

Date

3-26-2026

Committee Chair

LaBonte, Don

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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