Abstract
BackgroundModern watermelon (Citrullus lanatus L.) cultivars share a narrow genetic base due to many years of selection for desirable horticultural qualities. Wild subspecies within C. lanatus are important potential sources of novel alleles for watermelon breeding, but successful trait introgression into elite cultivars has had limited success. The application of marker assisted selection (MAS) in watermelon is yet to be realized, mainly due to the past lack of high quality genetic maps. Recently, a number of useful maps have become available, however these maps have few common markers, and were constructed using different marker sets, thus, making integration and comparative analysis among maps difficult. The objective of this research was to use single-nucleotide polymorphism (SNP) anchor markers to construct an integrated genetic map for C. lanatus.ResultsUnder the framework of the high density genetic map, an integrated genetic map was constructed by merging data from four independent mapping experiments using a genetically diverse array of parental lines, which included three subspecies of watermelon. The 698 simple sequence repeat (SSR), 219 insertion-deletion (InDel), 36 structure variation (SV) and 386 SNP markers from the four maps were used to construct an integrated map. This integrated map contained 1339 markers, spanning 798 cM with an average marker interval of 0.6 cM. Fifty-eight previously reported quantitative trait loci (QTL) for 12 traits in these populations were also integrated into the map. In addition, new QTL identified for brix, fructose, glucose and sucrose were added. Some QTL associated with economically important traits detected in different genetic backgrounds mapped to similar genomic regions of the integrated map, suggesting that such QTL are responsible for the phenotypic variability observed in a broad array of watermelon germplasm.ConclusionsThe integrated map described herein enhances the utility of genomic tools over previous watermelon genetic maps. A large proportion of the markers in the integrated map are SSRs, InDels and SNPs, which are easily transferable across laboratories. Moreover, the populations used to construct the integrated map include all three watermelon subspecies, making this integrated map useful for the selection of breeding traits, identification of QTL, MAS, analysis of germplasm and commercial hybrid seed detection.
Highlights
Modern watermelon (Citrullus lanatus L.) cultivars share a narrow genetic base due to many years of selection for desirable horticultural qualities
A total of 386 single-nucleotide polymorphism (SNP) loci were segregating in the latter population, allowing the integration of 244449 data points generated from four mapping populations representing eight watermelon parental accessions (Table 1)
In this study, we developed an integrated map which consisted of 698 simple sequence repeat (SSR), 219 InDels, 36 structure variation (SV) and 386 SNP markers from four independent mapping populations, which includes the three subspecies of watermelon
Summary
Modern watermelon (Citrullus lanatus L.) cultivars share a narrow genetic base due to many years of selection for desirable horticultural qualities. The long term cultivation and selection of watermelon for desirable horticultural qualities resulted in modern watermelon cultivars with a narrow genetic base and susceptibility to a large number of diseases and pests [1]. Several critical steps that include accurate phenotyping for disease or pest resistance, high density genetic mapping and genome sequencing and assembly studies are needed as part of continuous efforts to utilize citron and egusi type germplasm for the improvement of elite watermelon cultivars. A number of integrated linkage maps have been developed in economically important crops to increase marker density and integrate the QTL information, including melon (Cucumis melo L.) [6], grapevine (Vitis vinifera L.) [7], lettuce (Lactuca sativa L.) [8], maize (Zea mays L.) [9], sorghum (Sorghum bicolor L.) [10], red clover (Trifolium pratense L.) [11], ryegrass (Lolium ssp L.) [12] and wheat (Triticum aestivum L.) [13]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
