Unveiling the genetic landscape of Bletilla striata: conservation challenges in a medicinal orchid under threat

Populations of Bletilla striata, an essential traditional Chinese medicinal plant, are undergoing drastic declines mainly driven by anthropogenic pressures and climate change. Such declines have important demographic effects, potentially reducing the genetic diversity and gene flow while pushing this species into an extinction vortex. To develop comprehensive conservation and utilization strategies for B. striata, it is fundamental to understand its genetic landscape first. This study aims to assess the genetic diversity and population structure of B. striata to inform conservation strategies using eight nuclear microsatellites (nrSSR) loci and three chloroplast (cpDNA) loci. Results from nrSSR revealed that western populations exhibited 35.6 % higher allelic richness compared to southern populations, while cpDNA analysis showed southern populations exhibited three times higher haplotype diversity compared to western populations. Allelic richness is not strongly influenced by latitude (P = 0.737), but haplotype diversity decreased by 71.4 % with increasing latitude (P = 0.041), indicating that haplotype diversity is strongly influenced by limited dispersal northward. Considering the historical migration and cultivation practices in China, we speculated that artificial planting and breeding have increased allelic richness in western populations but not haplotype diversity, possibly due to strong pollen flow between cultivated and natural populations. This study highlights the need for targeted conservation efforts in the lower ranges of the Yangtze River and southern China, focusing on preserving the high haplotype diversity of B. striata.