A genetic linkage map for watermelon derived from a testcross population: (Citrullus lanatus var. citroides × C. lanatus var. lanatus) × Citrullus colocynthis

Abstract

A genetic linkage map was constructed for watermelon using a testcross population [Plant Accession Griffin 14113 ( Citrullus lanatus var. citroides) x New Hampshire Midget (NHM; C. lanatus var. lanatus)] x U.S. Plant Introduction (PI) 386015 ( Citrullus colocynthis). The map contains 141 randomly amplified polymorphic DNA (RAPD) markers produced by 78 primers, 27 inter-simple sequence repeat (ISSR) markers produced by 17 primers, and a sequence-characterized amplified region (SCAR) marker that was previously reported as linked (1.6 cM) to race-1 Fusarium wilt [incited by Fusarium oxysporum Schlechtend.:Fr. f. sp. niveum (E.F.Sm.) W.C. Synder & H.N. Hans] resistance in watermelon. The map consists of 25 linkage groups. Among them are a large linkage group that contains 22 markers covering a mapping distance of 225.6 cM and six large groups each with 10-20 markers covering a mapping distance of 68.8 to 110.8 cM. There are five additional linkage groups consisting of 3-7 markers per group, each covering a mapping distance of 36.5 to 57.2 cM. The 13 remaining linkage groups are small, each consisting of 2-11 markers covering a mapping distance of 3.5-29.9 cM. The entire map covers a total distance of 1,166.2 cM with an average distance of 8.1 cM between two markers. This map is useful for the further development of markers linked to disease resistance and watermelon fruit qualities.

Genotyping by sequencing for SNP discovery and genetic mapping of resistance to race 1 of Fusarium oxysporum in watermelon

“…In grapevine (Vitis vinifera), Barba et al (2014) allowed up to 10% missing data in GBS-derived SNPs for genetic map construction. The genetic map obtained in this study was significantly longer (3,955.2 cM) than that obtained in previous watermelon mapping studies (Hashizume et al, 2003;Hawkins et al, 2001;Levi et al, 2002Levi et al, , 2006Levi et al, , 2011Ren et al, 2012Ren et al, , 2014Sandlin et al, 2012). Massive elongation of the genetic maps often occurs when working with SNP data generated through GBS due to high levels of genotyping errors that tend to over-estimate the number of double cross-over events (Barba et al, 2014;Spindel et al, 2013).…”

Analysis based on RAPD and ISSR Markers Reveals Closer Similarities among Citrullus and Cucumis Species than with Praecitrullus fistulosus (Stocks) Pangalo

“…Although there is wide genetic distance between C. lanatus and C. colocynthis, there are no strong genetic barriers between these two Citrullus species. The F1 hybrid plants between C. lanatus and C. colocynthis may occasionally be self-sterile, but the F1 plants can be readily backcrossed or testcrossed with C. lanatus or C. colocynthis plants (Jeffrey 1975;Zamir et al 1984;Levi et al 2002). Wide genetic distance exists between PIs of Cucumis and Citrullus species (overall, 8% genetic similarity; Figure 2).…”

A High Resolution Genetic Map Anchoring Scaffolds of the Sequenced Watermelon Genome

“…Several critical steps that include accurate phenotyping for disease or pest resistance, genetic mapping and genome sequencing and assembly studies are needed as part of continuous efforts of exploring and utilizing watermelon germplasm for the improvement of watermelon cultivars. There are limited genomic resources and genetic maps for watermelon [2], [3], [4] and there is a need to develop a saturated genetic map that represent the watermelon genome. Also, there is a need for a cytogenetic map that could be useful in the identification of watermelon chromosomes and demarcating possible structural differences between the cultivated watermelon and it's related Citrullus spp.…”

“…These maps were mainly based on isozymes [6], [7], RAPD (randomly amplified polymorphic DNA), RFLP (restriction fragment length polymorphism), AFLP (amplified fragment length polymorphism) and SRAP (sequence related amplified polymorphism) markers, and only a limited number of SSR (simple sequence repeat) markers were used [4], [8]. The genetic maps were constructed using F2, BC1, or testcross populations [2], [9], [10], [11]. No high density genetic linkage maps representing genome sequences have been reported in watermelon, which has a low genetic diversity among different cultivars.…”