Genetic mapping of a major codominant QTL associated with β-carotene accumulation in watermelon
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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 β-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 testcrosses of NY0016 with yellow and red fruited lines indicated a codominant 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 β-carotene accumulation in watermelon fruit. The QTL interval is approximately 20 cM on the genetic map and 2.4 Mb on the watermelon genome. Trait-linked marker was developed and used for validation of the QTL effect in segregating populations across different genetic backgrounds. This study is a step toward identification of a major gene involved in carotenoid biosynthesis and accumulation in watermelon. The codominant inheritance of β-carotene provides opportunities to develop, through marker-assisted breeding, β-carotene-enriched red watermelon hybrids.
KeywordsQTL Carotenoids Fruit color Watermelon Genotyping-by-sequencing
We gratefully acknowledge support from the “Center for the Improvement of Cucurbit Fruit Quality,” ARO, Israel. We also acknowledge partial support by US-Israel Binational Agricultural Research & Development (BARD) Senior Research Fellowship Program (USDA-BARD Agreement Number 58-6080-5-011F), and by USDA-National Institute of Food and Agriculture (NIFA), Specialty Crop Research Initiative (SCRI) grant number 2015-51181-24285. We also thank the USA National Watermelon Research and Promotion Board for their continual support; publication no. 211/2017 of the Agricultural Research Organization, Bet Dagan, Israel.
AG, AL, AM, and YT conceived and designed the study. LV, AM, and GT performed field experiments, phenotyping, and genotyping. AG, ZF, and SB analyzed the data. AG, SB, AL, WW, and YT wrote the paper. All authors discussed the results and approved the manuscript.
Funding for this research was provided by the Israeli Ministry of Agriculture Chief Scientist grant no. 20-01-0135.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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