The genome of melon (Cucumis melo L.). Genome amplification in the absence of recent duplication in an old widely cultivated species. The Genome of Melon (cucumis melo L.)

We report the genome sequence of melon (Cucumis melo L.), an important horticultural crop worldwide. We assembled 375 Mb, representing 83.3 % of the estimated melon genome. Using a genetic map containing 602 SNPs, we were able to anchor 316.3 Mb of sequence in 87 scaffolds, representing 87.5 % of the scaffold assembly. A total of 73,787 transposon copies were detected, representing 19.7% of the genome. We predicted 27,427 protein-coding genes, which we analyzed by reconstructing 22,218 phylogenetic trees, allowing mapping of the orthology and paralogy relationships of sequenced plant genomes. We observed the absence of recent whole genome duplications in the melon lineage since the ancient eudicot triplication and our data suggest that transposon amplification may in part explain the increased size of the melon genome when compared to the close relative cucumber. A low number of NBS-LRR disease resistance genes were annotated, suggesting the existence of specific defense mechanisms in this species. The reference genome was compared with that of its parental lines allowing the quantification of sequence variability in the species. The use of the genome sequence in these and future investigations will facilitate the understanding of evolution of cucurbits and the improvement of breeding strategies