Abstract
Watermelon (Citrullus lanatus L.) is an important horticultural crop that is grown worldwide and has a high economic value. To dissect the loci associated with important horticultural traits and to analyze the genetic and genomic information of this species, a high-density genetic map was constructed based on whole-genome resequencing (WGR), a powerful high-resolution method for single-nucleotide polymorphism (SNP) marker development, genetic map construction, and gene mapping. Resequencing of both parental lines and 126 recombinant inbred lines (RIL) resulted in the detection of 178,762 single-nucleotide polymorphism (SNP) markers in the parental lines at a sequencing depth greater than four-fold. Additionally, 2132 recombination bin markers comprising 103,029 SNP markers were mapped onto 11 linkage groups (LGs). Substantially more SNP markers were mapped to the genetic map compared with other recent studies. The total length of the linkage map was 1508.94 cM, with an average distance of 0.74 cM between adjacent bin markers. Based on this genetic map, one locus for fruit bitterness, one locus for rind color, and one locus for seed coat color with high LOD scores (58.361, 18.353, 26.852) were identified on chromosome 1, chromosome 8, and chromosome 3, respectively. These prominent loci were identified in a region of 6.16 Mb, 2.07 Mb, and 0.37 Mb, respectively. On the basis of current research, the high-density map and mapping results will provide a valuable tool for identifying candidate genes, map-based gene cloning, comparative mapping, and marker-assisted selection (MAS) in watermelon breeding.
Highlights
Watermelon [Citrullus lanatus (Thu nb.) Matsum. & Nakai (2n = 2x = 22)] is an important member of Cucurbitaceae that is commercially produced globally and China is currently both the top producer and consumer of watermelon, with a cultivated area of 189 million ha in 2016 (FAO, http://faostat.fao.org)
We aimed to identify candidate region for fruit bitterness, rind color, and seed coat color, which can facilitate the identification of candidate genes and marker-assisted selection breeding programs for watermelon
Phenotyping results were identified based on the three growth environments, and results were similar in all the environments
Summary
& Nakai (2n = 2x = 22)] is an important member of Cucurbitaceae that is commercially produced globally and China is currently both the top producer and consumer of watermelon, with a cultivated area of 189 million ha in 2016 (FAO, http://faostat.fao.org). One important prerequisite for constructing a high-density genetic map is the identification of numerous polymorphic markers. Genetic linkage maps were constructed for watermelon in several previous studies. These maps were constructed based on isozymes [3,4], randomly amplified polymorphic DNA (RAPD), restriction fragment length polymorphisms (RFLP), amplified fragment length polymorphisms (AFLP), sequence-related amplified polymorphism (SRAP) markers, and simple sequence repeat (SSR) markers [5,6,7]. The maps constructed with these techniques are low-density and have a higher number of linkage groups than anticipated
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