Evaluation of Genome Size, Chromosome Number and Karyotype in Zygophyllum xanthoxylon

Zygophyllum xanthoxylon, a super-xerophytic shrub in drylands, is widely used for afforestation in the arid and barren mountains of central Asia. Understanding the karyotype and genome size could provide basic information for genome sequencing of species. To date, few data on the DNA content and chromosomal characterization of Z. xanthoxylon have been reported. Here, we present both the karyotype analysis and genome size determination of Z. xanthoxylon based on the traditional pressing and flow cytometry methods. Chromosome counting showed that Z. xanthoxylon is diploid with a chromosome number of 22. Karyotype analysis revealed that the length of chromosomes ranges from 0.88 ± 0.08 μm to 2.36 ± 0.19 μm, the chromosomes are metacentric or submetacentric, and the karyotype formula is 2n = 2x = 22 = 18m + 4sm. Flow cytometry analysis estimated that the nuclear genome size of Z. xanthoxylon is 460 ± 7.05 Mbp. Interestingly, our results indicated the seedlings of Z. xanthoxylon exhibit endopolyploidy, which may confer better ecological adaptation. Collectively, the present study will provide an important cytological basis for the study of the origin, evolution and utilization of Z. xanthoxylon.