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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Research » Publications at this Location » Publication #428462
Research Project: Genomics and Genetic Improvement of Disease Resistance and Horticultural Characteristics of Watermelon, Broccoli, and Leafy Brassicas

Location: Vegetable Research

Title: Mapping QTLs influencing flowering time in a Citrullus amarus population

Author
item GANAPARTHI, VENKAT - Clemson University
item WECHTER, WILLIAM - Clemson University
item Levi, Amnon
item BRANHAM, SANDRA - Clemson University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2025
Publication Date: 12/10/2025
Citation: Ganaparthi, V., Wechter, W., Levi, A., Branham, S. 2025. Mapping QTLs influencing flowering time in a Citrullus amarus population. Theoretical and Applied Genetics. https://doi.org/10.1007/s00122-025-05104-6.
DOI: https://doi.org/10.1007/s00122-025-05104-6

Interpretive Summary: Watermelon is an important vegetable crop grown in 44 states in the U.S.A. Flowering time is critical for watermelon growers. This is since harvesting watermelon early in the summer has greater monetary profit to growers. Identifying genetic resources and genes affecting early flowering in watermelon should be highly useful for breeders to develop early flowering varieties. In this study, ARS scientists collaborated with scientists at Clemson University on utilizing the USDA germplasm (genetic material) collection of watermelon and in using genomic technologies to identify genetic resources and genes controlling flowering time in watermelon. The genetic material and genomic data developed in this study should be useful to seed company and public researchers and breeders aiming to develop early flowering elite watermelon cultivars.

Technical Abstract: Inbred lines of Citrullus amarus, a wild relative of cultivated watermelon, are widely used as rootstocks to control soil-borne diseases for watermelon (Citrullus lanatus) production. The most commonly used watermelon rootstock, ‘Carolina strongback’ (Syngenta, Basel, Switzerland) flowers weeks later than commercial watermelon cultivars, which delays the onset of female flowering (DFF) of the scion, leading to an undesirable delay in fruit maturity and harvesting. Understanding the genetics of DFF in a C. amarus population will facilitate the development of rootstocks with the early flowering habits preferred for commercial production. A recombinant inbred line population (N=129 lines) developed between C. amarus lines, USVL246-FR2 and USVL114, was evaluated in field trials in spring and fall of 2022 and 2023 for DFF and days to fruiting (DFT) after being transplanted into the field. The correlation between DFF and DFT is 0.92. Broad sense heritability of DFF and DFT were 0.23 and 0.31, respectively. Two QTLs influencing both the DFF and DFT across the seasons and years were identified at 90.5 and 56.0 cM on chromosome 3 and together explained 39.67 percent variance of DFF. Two additional QTLs associated with DFF, were season-specific with a spring and a fall QTL on chromosome 10 and on the proximal end of chromosome 3, respectively. Genes coding for putative proteins involved in inducing anthesis, activation and regulation of FT proteins were identified in the 1.5 LOD interval of the stable major QTLs on chromosome 3.