Mapping the genetic architecture of low‐temperature stress tolerance in citron watermelon

• Published in: The plant genome Vol. 17; no. 2; pp. e20443 - n/a
• Main Authors: Katuuramu, Dennis N., Levi, Amnon, Wechter, William P.
• Format: Journal Article
• Language: English
• Published: United States Wiley 01.06.2024
• ISSN: 1940-3372; 1940-3372
• DOI: 10.1002/tpg2.20443

Sweet‐fleshed watermelon (Citrullus lanatus) is an important vegetable crop of the 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 (Citrullus amarus) accessions were obtained from the USDA's National Plant Germplasm Repository System gene bank in Griffin, GA. The accessions were genotyped using whole genome resequencing to generate single nucleotide polymorphisms (SNPs) molecular markers and screened under cold‐stressed and non‐stressed control conditions. Four low‐temperature stress tolerance related traits including shoot biomass, vine length, maximum quantum efficiency of photosystem II, and chlorophyll content were measured under cold‐stressed and non‐stressed control treatment conditions. Correlation analysis revealed the presence of positive relationships among traits. Broad‐sense heritability for all traits ranged from 0.35 to 0.73, implying the presence of genetic contributions to the observed phenotypic variation. Genomic regions underlying these traits across several citron watermelon chromosomes were identified. Four low‐temperature stress tolerance related putative candidate genes co‐located with the peak SNPs from genome‐wide association study. These genomic regions and marker information could potentially be used in molecular breeding to accelerate genetic improvements for low‐temperature stress tolerance in watermelon. Core Ideas A panel of citron watermelon accessions was extensively phenotyped for cold stress tolerance related traits under both stressed and non‐stressed control conditions. Using 122 accessions and 2,126,759 genome‐wide single nucleotide polymorphism markers, genome‐wide association study models were evaluated to discover marker‐trait associations. Genomic loci and candidate genes were identified and will be useful in the improvement of watermelon varieties for cold stress tolerance traits. Plain Language Summary Cold stress is a destructive abiotic stressor to plants of tropical origin such as watermelon when grown in temperate regions. A total of 122 citron watermelon (Citrullus amarus) accessions were screened for cold stress tolerance traits including shoot biomass, vine length, maximum quantum efficiency of photosystem II, and chlorophyll content. The citron watermelon accessions were genotyped with 2,126,759 genome‐wide markers single nucleotide polymorphisms (SNPs) molecular markers generated through whole‐genome resequencing. High broad‐sense heritability varied from low to high suggesting presence of genetic control to the cold stress tolerance traits. Trait mapping using the GWAS methodology detected genomic regions, SNP markers, and candidate genes associated with the cold stress tolerance traits. The significant SNP markers explained 2.1% ‐ 21.8% of the phenotypic variation, highlighting the quantitative inheritance nature of these traits.