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Research Project: Genomics and Genetic Improvement of Disease Resistance and Horticultural Characteristics of Watermelon, Broccoli, and Leafy Brassicas

Location: Vegetable Research

Title: Genetic control of flowering time and fruit yield in citron watermelon

item KATUURAMU, DENNIS - US Department Of Agriculture (USDA)
item Levi, Amnon
item WECHTER, WILLIAM - Clemson University

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2023
Publication Date: 10/10/2023
Citation: Katuuramu, D.N., Levi, A., Wechter, W.P. 2023. Genetic control of flowering time and fruit yield in citron watermelon. Horticulture Research. 14.

Interpretive Summary: Watermelon is an economically important vegetable crop. Early flowering and high yield are crucial traits required in modern watermelon varieties. Information on phenotypic and genetic variability (molecular markers) is needed to develop watermelon varieties that are early flowering (and maturing) and high yielding. There is limited information on the inheritance and genetic control of flowering time and yield traits in watermelon. In this study, a collection of USDA citron watermelon accessions was evaluated for flowering time and fruit yield traits under field conditions over two years. A genetic mapping methodology called genome-wide association study was utilized to detect genomic markers associated with flowering time and fruit yield traits. The new molecular markers will be useful in improving watermelon for earliness to flower and maturity and yield performance via marker-assisted breeding.

Technical Abstract: Flowering time and fruit yield are important traits in watermelon crop improvement. There is limited information on the inheritance and genomic loci underlying flowering time and yield performance. A total of 125 citron watermelon accessions were evaluated in field trials over two growing seasons for days to male and female flowers, fruit count, fruit weight, and fruit yield. The germplasm was genotyped with more than two million single nucleotide polymorphisms (SNPs) markers generated via whole-genome resequencing. Trait mapping was conducted using genome-wide association study (GWAS). Broad-sense heritability for all traits ranged from moderate to high, indicating that genetic improvement through breeding and selection is feasible. Significant marker-trait associations were uncovered for days to female flower (chromosomes Ca04, Ca05, Ca08, and Ca09), fruit count (on Ca02, Ca03, and Ca05), fruit weight (on Ca02, Ca06, Ca08, Ca10, and Ca11), and fruit yield on chromosomes Ca05, Ca07, and Ca09. The phenotypic variability explained by the peak SNPs ranged from 1.6 to 25.4 highlighting the complex genetic architecture of the evaluated traits. These results lay a foundation for marker-assisted trait introgression of flowering time and fruit yield components in watermelon.