Objective Based on Simple Sequence Repeat (SSR) molecular marker technology, this study conducted investigations into the genetic diversity and population structure of Camellia semiserrata populations in Dongguan, aiming to provide a theoretical basis for elucidating the genetic domestication and adaptive mechanisms of C. semiserrata and facilitating the molecular breeding of elite varieties.

Method A total of 200 randomly selected germplasm samples were collected from nearly 533 hm² C. semiserrata forest in Zhangmutou Forest Farm, Dongguan. Using polymerase chain reaction (PCR) amplification and fluorescent capillary electrophoresis detection technology, SSR polymorphic primer screening and SSR locus genotyping were performed. Based on the genotyping results, the number of alleles per locus was counted, and population genetic parameters including Polymorphism Information Content (PIC), Shannon's Diversity Index, Nei's genetic diversity index, observed heterozygosity, expected heterozygosity, inbreeding coefficient (Fis), and genetic differentiation coefficient (Fst) were calculated. Additionally, population structure analysis and unweighted pair group method with arithmetic mean (UPGMA) cluster analysis were conducted to evaluate the genetic diversity level of the germplasm samples population and elucidate its population structure.

Result A total of 20 pairs of polymorphic SSR primers were screened out, and 187 alleles were amplified. For the SSR loci, the average number of alleles was 9.4, the average effective number of alleles (Ne) was 2.832, and the average PIC was 0.5854. The average Shannon's Diversity Index was 1.028, and the average Nei's genetic diversity index was 0.6230. For the C. semiserrata germplasm samples population, the average observed heterozygosity and expected heterozygosity were 0.4690 and 0.6248, respectively. The average Fis was 0.127, and the average Fst was 0.12. Population genetic structure analysis divided the germplasm samples population into 6 clusters, with admixed individuals accounting for 41%. UPGMA cluster analysis revealed that the population exhibited complex grouping patterns and genetic backgrounds.

Conclusion The 20 pairs of polymorphic SSR primers screened in this study are suitable for investigating the genetic diversity and population structure of C. semiserrata populations. The C. semiserrata population in Dongguan exhibits high levels of genetic diversity and heterozygosity, accompanied by a moderate degree of genetic differentiation, as well as a complex population structure and genetic background.