A chromosome-scale genome assembly of Timorese crabgrass (Digitaria radicosa): a useful genomic resource for the Poaceae

Abstract

Timorese crabgrass (Digitaria radicosa) is a grass species commonly found in Southeast Asia and Oceania. Digitaria species have high intraspecific and interspecific genetic and phenotypic diversity, suggesting their potential usefulness as a genetic resource. However, as the only high-quality reference genome available is for a tetraploid Digitaria species, a reference genome of the diploid species D. radicosa would be a useful resource for genomic studies of Digitaria and Poaceae plants. Here, we present a chromosome-level genome assembly of D. radicosa and describe its genetic characteristics; we also illustrate its usefulness as a genomic resource for Poaceae. We constructed a 441.6 Mb draft assembly consisting of 61 scaffolds with an N50 scaffold length of 41.5 Mb, using PacBio HiFi long reads. Thirty scaffolds, encompassing 440.8 Mb, were anchored to nine pseudochromosomes. We predicted 26,577 protein-coding genes, reaching a BUSCO score of 96.5%. To demonstrate the usefulness of the D. radicosa reference genome, we investigated the evolution of Digitaria species and the genetic diversity of Japanese Digitaria plants based on our new reference genome. We also defined the syntenic blocks between D. radicosa and Poaceae crops and the diverse distribution of representative resistance genes in D. radicosa. The D. radicosa reference genome presented here should help elucidate the genetic relatedness of Digitaria species and the genetic diversity of Digitaria plants. In addition, the D. radicosa genome will be an important genomic resource for Poaceae genomics and crop breeding.