Date of Graduation

8-2023

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Shi, Ainong

Committee Member

Dickson, Ryan W.

Second Committee Member

Joshi, Neelendra K.

Keywords

Drought stress; Fusarium; Tomato crop; Common beans; Genome-wide association study; Genomic prediction

Abstract

Drought stress and Fusarium wilt disease present significant challenges to plant growth and agricultural productivity, particularly affecting crops such as tomato and common beans. To address these issues, researchers have extensively evaluated germplasm collections under field and greenhouse conditions to identify genotypes with drought tolerance and disease resistance. This study aimed to achieve two objectives. Firstly, we conducted a phenotypic evaluation of drought tolerance in USDA tomato germplasm to identify drought-tolerant accessions for future breeding programs targeting enhanced drought tolerance in tomato cultivars. Secondly, we conducted a genome-wide association study (GWAS) and genomic prediction (GP) on USDA common bean germplasm using publicly available disease response and SNP datasets to identify single nucleotide polymorphism (SNP) markers and candidate genes associated with Fusarium wilt resistance. Chapter 1 describes the evaluation of tomato accessions in a greenhouse at the Arkansas Agricultural Research and Extension Center, Fayetteville, AR. The experiment involved planting tomato seeds in pots and subjecting the plants to drought conditions alongside control sets under optimal irrigation. After 35 days of growth, we withheld water from the drought-treated plants for approximately 10 days until the more susceptible plants began to die off. We collected data on leaf wilting, leaf rolling, plant height, and leaf chlorophyll content from both the drought-treated and control groups to understand how different genotypes respond to drought stress. This study identified four highly drought-tolerant tomato accessions, which can be valuable for breeding programs to develop elite drought-tolerant tomato cultivars. Chapter 2 focuses on GWAS and GP for Fusarium wilt resistance in 157 USDA common bean accessions. These accessions were previously evaluated by (Brick et al., 2006) for resistance to Fusarium wilt caused by Fusarium oxysporum (Fop) race 1 and race 4 in a greenhouse condition. We utilized a dataset from this evaluation and performed comprehensive GWAS and GP analyses using SNP markers from the BARCBean6K_3 Infinium BeadChips. As a result, we identified significant SNP markers associated with Fusarium wilt resistance and the discovery of candidate genes, shedding light on the genetic factors contributing to resistance in common beans. The study also explores the potential of genomic prediction techniques for predicting resistance to Fusarium wilt, offering valuable insights into marker-assisted and genomic selection strategies for breeding programs. In conclusion, this thesis contributes important knowledge on drought tolerance in tomatoes and Fusarium wilt resistance in common beans. The findings can serve as a foundation for future breeding efforts focused on improving these traits in crop cultivars, ultimately enhancing agricultural productivity and sustainability.

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