Genetic structure of cultivated Zanthoxylum species investigated with SSR markers

Zanthoxylum is an economically and ecologically important genus of the Rutaceae family, of which Z. bungeanum and Z. armatum have a long history of cultivation in China. However, how the natural processes such as selection and drift and agriculture practices have influenced the genetic variation of cultivated Zanthoxylum species during long-term domestication remains elusive. Herein, we determined the population genetic structure of current widely cultivated Zanthoxylum species, Z. bungeanum and Z. armatum. Microsatellite markers revealed a high level of genetic variation and significant genetic differentiation for both species despite Z. bungeanum showed higher genetic diversity than Z. armatum. AMOVA indicated that most of the genetic variation exists within individuals rather than among provenances for both species. Population structure analyses generated three distinct groups within the entire accessions. All Z. bungeanum accessions were distinguished into two major geographic groups, north and south groups, with Qinling Mountains as the main geographic barrier to gene flow while a significant genetic differentiation was observed between cultivated and wild Z. armatum accessions. Mantel test of Z. bungeanum displayed a significant correlation between genetic and geographic distances within each inferred group but no correlation between genetic and geographic distance was observed when comparing genetic and geographic distances focusing only on pairwise of north vs. south provenances, ruling out the hypothesis that gene flow between north and south provenances followed an isolation-by-distance model. Our research provided a fundamental genetic profile that will improve the conservation and responsible exploitation of the extant germplasm of Zanthoxylum.