Assessment of Genetic Diversity and Population Structure of the Endangered Astragalus exscapus subsp. transsilvanicus through DNA-Based Molecular Markers

Astragalus exscapus L. subsp. transsilvanicus (Schur) Nyár. (Fabaceae) is a rare plant endemic to the Transylvanian Plateau, represented by 24 identified populations. Limited information on the genetic variation and population structure is available, which obstructs efficient measures for conservation strategy. The present study aimed to analyze the genetic diversity and population structure of eight populations of A. exscapus subsp. transsilvanicus revealed by sequence-related amplified polymorphism (SRAP) markers. A total of 164 bands were amplified, 96.7% of which (159) were polymorphic. Nei’s gene diversity index (He) was estimated to be 0.228 at the population level and 0.272 at the subspecies level. The genetic differentiation among populations (Gst) was 0.165, which indicated a low proportion of total genetic diversity. The analysis of molecular variance (AMOVA) indicated that 17% of the total variation of A. exscapus subsp. transsilvanicus is found among the populations, while 83% was found within the populations. A UPGMA dendrogram, principal coordinate analysis, and the STRUCTURE software grouped the populations into two clusters uncorrelated with the provenience of the 125 individuals, which might be attributed to fragmentation processes, insect pollination, population size, and specific environmental conditions of the habitats.