An improved draft genome sequence of hybrid Populus alba ×  Populus glandulosa

Abstract

Populus alba ×  P. glandulosa clone 84 K, derived from South Korea, is widely cultivated in China and used as a model in the molecular research of woody plants because of high gene transformation efficiency. Here, we combined 63-fold coverage Illumina short reads and 126-fold coverage PacBio long reads to assemble the genome. Due to the high heterozygosity level at 2.1% estimated by k-mer analysis, we exploited TrioCanu for genome assembly. The PacBio clean subreads of P. alba ×  P. glandulosa were separated into two parts according to the similarities, compared with the parental genomes of P. alba and P. glandulosa. The two parts of the subreads were assembled to two sets of subgenomes comprising subgenome A (405.31 Mb, from P. alba) and subgenome G (376.05 Mb, from P. glandulosa) with the contig N50 size of 5.43 Mb and 2.15 Mb, respectively. A high-quality P. alba ×  P. glandulosa genome assembly was obtained. The genome size was 781.36 Mb with the contig N50 size of 3.66 Mb and the longest contig was 19.47 Mb. In addition, a total of 176.95 Mb (43.7%), 152.37 Mb (40.5%) of repetitive elements were identified and a total of 38,701 and 38,449 protein-coding genes were predicted in subgenomes A and G, respectively. For functional annotation, 96.98% of subgenome A and 96.96% of subgenome G genes were annotated with public databases. This de novo assembled genome will facilitate systematic and comprehensive study, such as multi-omics analysis, in the model tree P. alba ×  P. glandulosa.

Keywords

Genome assembly / Gene annotation / Hybrid poplar / Populus alba ×  p. glandulosa cl. 84 K

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