A chromosome-level genome assembly provides insights into the local adaptation of Tamarix austromongolica in the Yellow River Basin, China.

ABSTRACT

Tamarix austromongolica is endemic to the Yellow River Basin and has adapted to diverse ecological settings in the region, including the arid areas of northwestern China and the saline soil regions of the Yellow River Delta. However, the genetic basis of its local adaptation remains unclear. We report a chromosome-level assembly of the T. austromongolica genome based on PacBio high-fidelity sequencing and Hi-C technology. The 12 pseudochromosomes cover 98.44% of the 1.32 Gb assembly, with a contig N50 of 52.57 Mb and a BUSCO score of 98.2%. The genome comprises 913.6 Mb (68.83%) of repetitive sequences and 22,374 protein-coding genes. Genome evolution analyses suggest that genes under positive selection and significantly expanded gene families have facilitated T. austromongolica's adaptability to diverse environmental factors and high resistance to diseases. Using genotyping-by-sequencing, we conducted population structure and selection analyses of 114 samples from 15 sites. Two genetic groups were identified, and 114 and 289 candidate genes were assigned to the populations of the northwestern and eastern parts of the Yellow River, respectively. Furthermore, we discovered numerous candidate genes associated with high-altitude adaptability and salt tolerance. This research provides valuable genomic resources for the evolutionary study and genetic breeding of tamarisk.