Genome survey sequencing and genetic background characterization of yellow horn based on next-generation sequencing.

Yellowhorn (Xanthoceras sorbifolium Bunge) is an important wood oil tree species, with high ornamental and medicinal value. Nevertheless, genomic information of yellowhorn is currently unavailable. Here, for the first time, we conducted a genome survey of two yellowhorn cultivars, Zhongshi 4 and Zhongshi 9, which had distinct differences on the phenotype and drought resistance, to obtain knowledge on the genomic information by next generation sequencing (NGS). Meanwhile, its genome size was estimated using flow cytometry. As a result, the whole genome survey of Zhongshi 4 and Zhongshi 9 generated 34.40 and 39.55 GB sequence data. The genome size of Zhongshi 4 and Zhongshi 9 estimated were about 536.58 Mb and 569.52 Mb, which were closed to results of flow cytometry. The heterozygosity rates were calculated to be 0.75% and 0.89%, and the repeat rates were 60.08% and 62.00%. These reads were assembled into 1024,373 and 885,404 contigs with a N50 length of 1005 bp and 1219 bp, respectively, which were further assembled into 714,369 and 686,128 scaffolds with scaffold N50 length of ~ 1963 bp and ~ 1938 bp, total length of 386,915 Kb and 391,904 Kb. These results indicated that there was little difference in genome size and complexity among different cultivars. In addition, 63137 and 65271 high-quality genomic simple sequence repeat (SSR) markers in Zhongshi 4 and Zhongshi 9 were generated. We suggest that the technologies combining Illumina and PacBio, assisted by Hi-C and matching assemble software should be used to one of two yellowhorn cultivars genome sequencing. The result will help to design whole genome sequencing strategies for yellowhorn, and provided a large amount of gene resources for further excavation and utilization of yellowhorn.