Chloroplast DNA phylogeography reveals genetic divergence of bermudagrass along latitudinal and longitudinal gradients in China

Great genetic variation in bermudagrass [Cynodon dactylon (L.) Pers.] make it adapt to various environment of widely distributed regions and present valuable wild germplasm for turfgrass breeding. Understanding geographic distribution of genetic diversification of bermudagrass along latitudinal and longitudinal gradients is favor of assessing genetic variation and diverse germplasm conservation. The study explored genetic variability and phylogeographic structure of 28 populations using three chloroplast intergenic spacer regions sequences. Bermudagrass populations at different latitudes exhibited a high level of genetic differentiation from populations at different longitudes. Populations at different latitudes indicated higher gene flow than populations at different longitudes, which attributed to higher genetic variation within population along the latitudinal gradient than longitudinal gradient. Contrast to apparent phylogeographic structure in populations along the latitudinal gradient, majority haplotypes sharing occurred in populations along the longitudinal gradient. Populations at high-latitudes showed distinct genetic diversity and haplotypes from populations at mid-latitudes. The Dabieshan and Nanling Mountains acted as the geographic barriers along the latitudinal gradient, leading to the intraspecific phylogeographic subdivision and divergence. Our study is valuable to better set up evolutionary significant units and formulate appropriate strategies for conserving genetic resources of bermudagrass.