
An improved chromosome-level genome assembly of perennial ryegrass (Lolium perenne L.) corrects structural errors, providing a high-quality reference for research.


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This work is an update and extension of the previously published article “Ultralong Oxford Nanopore Reads Enable the Development of a Reference-Grade Perennial Ryegrass Genome Assembly”, by Frei et al.. The published genome assembly of the doubled haploid perennial ryegrass ( Lolium perenne L.) genotype Kyuss marked a milestone for forage grass research and breeding. However, order and orientation errors may exist in the pseudo-chromosomes of Kyuss, since barley ( Hordeum vulgare L.), which diverged 30 million years ago from perennial ryegrass, was used as the reference to scaffold Kyuss. To correct for structural errors possibly present in the published Kyuss assembly, we de novo assembled the genome again and generated 50-fold coverage high-throughput chromosome conformation capture (Hi-C) data to assist pseudo-chromosome construction. The resulting new chromosome-level assembly showed improved quality with high contiguity (contig N50 = 120 Mb), high completeness (total BUSCO score = 99%), high base-level accuracy (QV = 50) and correct pseudo-chromosome structure (validated by Hi-C contact map). This new assembly will serve as a better reference genome for Lolium spp. and greatly benefit the forage and turf grass research community.

### Competing Interest Statement

The authors have declared no competing interest.

An improved chromosome-level genome assembly of perennial ryegrass (Lolium perenne L.)

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An Improved Chromosome-Level Genome Assembly of Perennial Ryegrass (Lolium perenne L.)


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Researchers have assembled a high-quality, chromosome-scale reference genome for the invasive Caucasian dwarf goby (Knipowitschia cf. caucasica) using a combination of sequencing technologies, providing a valuable resource for understanding the species' invasion biology and adaptation mechanisms.


The Caucasian dwarf goby Knipowitschia cf. caucasica is a new invasive alien Gobiidae spreading in the Lower Rhine since 2019. Little is known about the invasion biology of the species and further investigations to reconstruct the invasion history are lacking genomic resources. We assembled a high-quality chromosome-scale reference genome of Knipowitschia cf. caucasica by combining PacBio, Omni-C and Illumina technologies. The size of the assembled genome is 956.58 Mb with a N50 scaffold length of 43 Mb, which includes 92.3 % complete Actinopterygii Benchmarking Universal Single-Copy Orthologs. 98.96 % of the assembly sequence was assigned to 23 chromosome-level scaffolds, with a GC-content of 42.83 %. Repetitive elements account for 53.08 % of the genome. The chromosome-level genome contained 26,404 transcripts with 23,210 multi-exons, of which 26,260 genes were functionally annotated. In summary, the high-quality genome assembly provides a fundamental basis to understand the adaptive advantage of the species.

### Competing Interest Statement

The authors have declared no competing interest.

Chromosome level genome reference of the Caucasian dwarf goby Knipowitschia cf. caucasica, a new alien Gobiidae invading the River Rhine

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De Novo Genome Assembly of the Invasive Caucasian Dwarf Goby (Knipowitschia cf. caucasica) from the Rhine River
