Abstract: Rhododendron is one of the ten traditional famous flowers in China and has high ornamental value.However,genetic relationships among its cultivars are complex,and traditional classification methods cannot accurately reflect their genetic background.To investigate the genetic relationships between the naturally variant new Rhododendron'Mingshanhong’ and the main local germplasms at its discovery site,as well as their genetic diversity,the 'Mingshanhong’ and six rhododendron germplasms collected from the discovery site in Shouning County were used as materials and analyzed through phenotypic characterization and ISSR molecular markers.The results showed that 10 primers amplified a total of 97 bands,of which 91 were polymorphic,with a percentage of polymorphic bands of 93.81%.Nei’s genetic distances ranged from 0.3700~0.8370.UPGMA clustering divided the seven materials into two major groups at a genetic similarity coefficient of 0.49:Rhododendron amesiae formed one group alone,and the remaining six cultivars formed another group.'Mingshanhong’ had a relatively close genetic relationship with the local R.simsii group,among which its genetic distance to Rhododendron 'Guoqihong’ was the smallest,suggesting that it is very likely derived from natural variation within the 'Guoqihong’ population.The cophenetic correlation coefficient r was 0.8833,indicating relatively high reliability of the clustering.It is concluded that 'Mingshanhong’ may have originated from natural variation of 'Guoqihong’;the genetic diversity of rhododendron germplasms in Shouning County was relatively high;and molecular clustering and phenotypic classification were asynchronous,reflecting the genetic complexity of rhododendron resources in this region.This study provides a reference for variety identification and resource conservation of 'Mingshanhong’.