Nuclear and organelle genome assemblies of five Cucumis melo L. accessions, Ananas, Canton, PI 414723, Vedrantais and Zhimali, belonging to diverse botanical groups

The construction of accurate whole genome sequences is pivotal for characterizing the genetic diversity of plant species, identifying genes controlling important traits, or understanding their evolutionary dynamics. Here, we generated the nuclear, mitochondrial and chloroplast high- quality assemblies of five melon ( Cucumis melo L.) accessions representing five diverse botanical groups, using the Oxford Nanopore sequencing technology. The accessions here studied included varied origins, fruit shapes, sizes, and resistance traits, providing a holistic view of melon genomic diversity.

The final chromosome-level genome assemblies ranged in size from 359 to 365 Mb, with approximately 25x coverage for four of them multiplexed in half of a PromethION flowcell, and 48x coverage for the fifth, sequenced individually in another half of a PromethION flowcell. Contigs N50 ranged from seven to 15 Mb for all the assemblies, and very long contigs reaching sizes of 20-25 Mb, almost compatible with complete chromosomes, were assembled in all the accessions. Quality assessment through BUSCO and Mercury indicated the high completeness and accuracy of the assemblies, with BUSCO values exceeding 96% for all accessions, and Mercury QV values ranging between 32 and 47.

We focused on the complex NLR resistance gene clusters to validate the accuracy of the assemblies in highly complex and repetitive regions. Through Nanopore adaptive sampling, we generated accurate targeted assemblies of these regions with a significantly higher coverage, enabling the comparison to our whole genome assemblies.

Overall, these chromosome-level assembled genomes constitute a valuable resource for research focused on melon diversity, disease resistance, evolution, and breeding applications.

Article Summary

This study presents high-quality nuclear, mitochondrial, and chloroplast genome assemblies for five diverse melon ( Cucumis melo L.) accessions, using Oxford Nanopore sequencing. The assemblies represent a broad spectrum of melon diversity, including differences in origin, fruit morphology, or resistance traits. The genomes, ranging from 359 to 365 Mb, were assembled at a chromosome level with high contiguity, and verified using different validation approaches. This study provides valuable insights for research on melon genetic diversity, disease resistance, and breeding applications. The genome data will be especially valuable for plant geneticists, breeders, and researchers working on crop improvement and resistance traits.