title: Comparative mapping in watermelon [Citrullus lanatus (Thunb.) Matsum. et Nakai].
abstract: The first single-nucleotide polymorphism (SNP) maps for watermelon [Citrullus lanatus (Thunb.) Matsum. et Nakai] were constructed and compared. Three populations were developed from crosses between two elite cultivars, Klondike Black Seeded × New Hampshire Midget (KBS × NHM), an elite cultivar and wild egusi accession, Strain II × PI 560023 (SII × Egusi) and an elite cultivar and a wild citron accession, ZWRM50 × PI 244019 (ZWRM × Citroides). The SII × Egusi and ZWRM × Citroides F(2) populations consisted of 187 and 182 individuals respectively while the KBS × NHM recombinant inbred line (RIL) population consisted of 164 lines. The length of the genetic maps were 1,438, 1,514 and 1,144 cM with average marker distances of 3.8, 4.2, and 3.4 cM for the KBS × NHM, SII × Egusi and ZWRM × Citroides populations, respectively. Shared markers were used to align the three maps so that the linkage groups (LGs) represented the 11 chromosomes of the species. Marker segregation distortion were observed in all three populations, but was highest (12.7 %) in the ZWRM × Citroides population, where Citroides alleles were favored. The three maps were used to construct a consensus map containing 378 SNP markers with an average distance of 5.1 cM between markers. Phenotypic data was collected for fruit weight (FWT), fruit length (FL), fruit width (FWD), fruit shape index (FSI), rind thickness (RTH) and Brix (BRX) and analyzed for quantitative trait loci (QTL) associated with these traits. A total of 40 QTL were identified in the three populations, including major QTL for fruit size and shape that were stable across genetic backgrounds and environments. The present study reports the first SNP maps for Citrullus and the first map constructed using two elite parents. We also report the first stable QTL associated with fruit size and shape in Citrullus lanatus. These maps, QTL and SNPs should be useful for the watermelon community and represent a significant step towards the potential use of molecular tools in watermelon breeding.
authors.affiliation: Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Athens, GA 30602, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Sandlin
authors.forename: Jason
authors.initials: J
authors.lastname: Prothro
authors.forename: Adam
authors.initials: A
authors.lastname: Heesacker
authors.forename: Nelly
authors.initials: N
authors.lastname: Khalilian
authors.forename: Rebecca
authors.initials: R
authors.lastname: Okashah
authors.forename: Wenwen
authors.initials: W
authors.lastname: Xiang
authors.forename: Eleni
authors.initials: E
authors.lastname: Bachlava
authors.forename: David G
authors.initials: DG
authors.lastname: Caldwell
authors.forename: Chris A
authors.initials: CA
authors.lastname: Taylor
authors.forename: Danelle K
authors.initials: DK
authors.lastname: Seymour
authors.forename: Victoria
authors.initials: V
authors.lastname: White
authors.forename: Eva
authors.initials: E
authors.lastname: Chan
authors.forename: Greg
authors.initials: G
authors.lastname: Tolla
authors.forename: Cathy
authors.initials: C
authors.lastname: White
authors.forename: Dolores
authors.initials: D
authors.lastname: Safran
authors.forename: Elaine
authors.initials: E
authors.lastname: Graham
authors.forename: Steven
authors.initials: S
authors.lastname: Knapp
authors.forename: Cecilia
authors.initials: C
authors.lastname: McGregor
mesh_terms: D002874:Chromosome Mapping / Q000379:methods*; D029773:Citrullus / Q000235:genetics*; D005638:Fruit / Q000033:anatomy & histology / Q000235:genetics; D005828:Genetics, Population; D018745:Genome, Plant / Q000235:genetics; D009929:Organ Size / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics; D019655:Quantitative Trait, Heritable