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Research Project: Harnessing Genomic Technologies Toward Improving Vegetable Health in Field and Controlled Environments

Location: Vegetable Research

Title: Mapping the genetic architecture of low-temperature stress tolerance in citron watermelon

item KATUURAMU, DENNIS - US Department Of Agriculture (USDA)
item LEVI, AMNON - US Department Of Agriculture (USDA)
item Wechter, William - Pat

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2024
Publication Date: 3/10/2024
Citation: Katuuramu, D.N., Levi, A., Wechter, W.P. 2024. Mapping the genetic architecture of low-temperature stress tolerance in citron watermelon. Horticulture Research. e20443.

Interpretive Summary: Watermelon is an important warm season vegetable crop of tropical origin. Low temperatures early in the growing season is a serious impediment to plant establishment, growth, and development for plant species of tropical origin such as watermelon. Cold stress tolerant watermelon genotypes and molecular markers are needed to develop resilient varieties. To date, no genetic studies on tolerance to cold stress have been conducted in watermelon. In this study, we evaluated a collection of USDA citron watermelon accessions for cold stress tolerance related traits and identified several plant introductions with tolerance to low-temperature stress. A genetic mapping methodology called genome-wide association analysis was utilized to detect genomic markers and candidate genes associated with tolerance to cold stress. The new molecular markers and tolerant USDA plant introductions will be useful in improving watermelon to better cope with low temperature conditions early in the growing season.

Technical Abstract: Sweet-fleshed watermelon is an important vegetable crop of tropical origin. It is widely grown and consumed around the world for its hydration and nutritional quality values. Low-temperature stress can affect early planting, seedling establishment, and expansion of crop production to new areas. A collection of 122 citron watermelon accessions were obtained from the USDA’s National Plant Germplasm Repository System gene bank in Griffin, Georgia, United States. The accessions were genotyped using whole genome resequencing to generate single nucleotide polymorphisms molecular markers and screened over two tests for four low-temperature stress tolerance related traits including shoot biomass, vine length, maximum quantum efficiency of photosystem II, and chlorophyll content. Correlation analysis revealed presence of positive relationships among traits. Broad-sense heritability for all traits ranged from 0.35 to 0.73 implying presence of genetic contributions to the observed phenotypic variation. Genomic regions underlying these traits were located on chromosomes Ca02, Ca04, Ca05, Ca06, and Ca08. Three low-temperature stress tolerance related putative candidate genes co-located with the peak SNPs on the above chromosomes. These genomic regions and marker information could potentially be used in molecular breeding to accelerate genetic improvement for low-temperature stress tolerance in watermelon.