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Title: Genetic mapping of a major co-dominant QTL associated with B-carotene accumulation in watermelon

Author
item Branham, Sandra
item VEXLER, LEA - Volcani Center (ARO)
item MEIR, AYALA - Volcani Center (ARO)
item TZURI, GALIL - Volcani Center (ARO)
item FRIEMAN, ZOHAR - Volcani Center (ARO)
item Levi, Amnon
item Wechter, William - Pat
item TADMOR, YAAKOV - Volcani Center (ARO)
item GUR, AMIT - Volcani Center (ARO)

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2017
Publication Date: 12/1/2017
Citation: Branham, S., Vexler, L., Meir, A., Tzuri, G., Frieman, Z., Levi, A., Wechter, W.P., Tadmor, Y., Gur, A. 2017. Genetic mapping of a major co-dominant QTL associated with B-carotene accumulation in watermelon. Molecular Breeding. 37:146. https://doi.org/10.1007/s11032-017-0747-0.
DOI: https://doi.org/10.1007/s11032-017-0747-0

Interpretive Summary: Carotenoids are considered important vitamin precursors and antioxidant molecules, beneficial in reducing the risk of cardiovascular diseases and cancer. Commercial watermelon contains the red carotenoid lycopene and there is an interest by consumers to enrich watermelon with various carotenoids to enhance watermelon health benefits. A watermelon with high concentrations of the deep orange color carotenoid pigment beta-carotene, which is the primary natural source of vitamin A, has been considered useful to breed for watermelon with high concentrations of both lycopene and beta-carotene, thereby increasing the nutritional value of watermelon. However, little is known about the genetic mode resulting in orange flesh watermelon. USDA, ARS, U.S. Vegetable Laboratory scientists in Charleston, SC, have collaborated with scientists at the Agricultural Research Organization, Israel, on evaluating beta-carotene concentration and used advanced genomic technology tools to identify the gene locus involved in production of the beta-carotene pigment in watermelon. The DNA markers associated with orange-flesh identified and developed in this study could be useful for University researchers and seed company breeders working to increase the nutritional value of watermelon.

Technical Abstract: The common flesh color of commercially grown watermelon is red due to the accumulation of lycopene. However, natural variation in carotenoid composition that exists among heirloom and exotic accessions, results in a wide spectrum of flesh colors. We previously identified a unique orange-flesh watermelon accession (NY0016) that accumulates mainly beta-carotene and no lycopene. We hypothesized this unique accession could serve as a viable source for increasing provitamin A content in watermelon. Here we characterize the mode of inheritance and genetic architecture of this trait. Analysis of test crosses of NY0016 with yellow and red fruited lines indicated a co-dominant mode of action as F1 fruits exhibited a combination of carotenoid profiles from both parents. We combined visual color phenotyping with genotyping-by-sequencing of an F2:3 population from a cross of NY0016 by a yellow fruited line, to map a major locus on chromosome 1, associated with beta-carotene accumulation in watermelon fruit. The quantitative trait loci (QTL) interval is approximately 20 cM on the genetic map and 2.4 Mb on the watermelon genome. This study is a step towards identification of a major gene involved in carotenoid biosynthesis and accumulation in watermelon. The co-dominant inheritance of beta-carotene provides opportunities to develop, through marker-assisted breeding, beta-carotene-enriched red watermelon hybrids.