Genetic Diversity and Population Structure Analysis in the Chinese Endemic Species Michelia crassipes Based on SSR Markers

Michelia crassipes Y. W. Law (Magnoliaceae) is endemic to China and is the only species with purple flowers in the genus Michelia. It is commonly used as an important parent for flower color improvement and hybrid breeding. M. crassipes is recognized as an endangered plant. An urgent need exists to explore the genetic diversity of M. crassipes to efficiently select hybrid parents and develop efficient conservation strategies. In this study, a total of 128 samples were selected from seven natural populations of M. crassipes to explore their genetic diversity and structure. A total of 14 microsatellite (SSR) markers with high polymorphism and repeatability were developed, and 218 alleles were detected. This study mainly revealed three results: (1) The parameters of expected heterozygosity (He = 0.536) and mean Shannon's information index (I = 1.121) revealed moderately high levels of genetic diversity for the M. crassipes natural population; (2) The genetic differentiation coefficient (Fst = 0.108) showed that there was a low level of genetic differentiation, and AMOVA indicated that genetic variation existed mainly within populations and that there was frequent gene exchange between populations; and (3) The population genetic structure analysis showed that seven natural populations originated from two ancestral groups, and the Mantel test revealed that genetic and geographical distances between populations were significantly correlated. Our study is the first to explore the genetic diversity and structure of the M. crassipes natural population, which provides an important reference for the collection, conservation and utilization of Michelia crassipes germplasm resources.