Genetic diversity and population structure of wild and cultivated Camellia tetracocca Chang assessed by ILP markers: insights for conservation of an endangered tea species

Qingshan Town, Guizhou Province, represents the core distribution area of wild Camellia tetracocca Chang and a key production area of ‘Pu’an hong’ tea. This region has a long history of tea cultivation and harbors rich tea germplasm resources. As an endemic and endangered tea species in Guizhou, C. tetracocca Chang is threatened by habitat fragmentation and genetic diversity loss, highlighting the urgent need for systematic genetic analysis and conservation research. To facilitate the conservation and utilization of tea germplasm in Qingshan Town, 192 tea accessions representing four populations (wild ancient tea plant Ⅰ, wild ancient tea plant Ⅱ, cultivated ancient tea plant, and cultivated tea plant) were analyzed for genetic diversity using intron length polymorphism (ILP) markers. A total of 180 alleles were detected across 40 ILP loci, with a mean observed alleles (Na) of 4.45. The average observed heterozygosity (Ho) was 0.22, expected heterozygosity (He) 0.59, and Nei’s gene diversity (H) 0.59. The mean Shannon’s information index (I) was 1.11, and the mean polymorphic information content (PIC) was 0.53. Structure analysis revealed that the 192 individuals could be divided into three subpopulations, which was consistent with the results of UPGMA clustering and principal coordinate analysis (PCoA). Furthermore, a core germplasm collection comprising of 29 accessions was successfully established. Our results indicate that the tea germplasm in Qingshan Town maintains high genetic diversity, and the constructed core germplasm collection effectively represents the genetic diversity of the whole collection. This study provides a theoretical foundation for breeding elite tea cultivars and conserving the genetic resources of this endangered tea species.