Establishment and application of SSR molecular markers system for Hydrangea macrophylla

【Objective】 To establish an SSR molecular marker system suitable for Hydrangea macrophylla in China， there by providing foundation for the conservation and utilization of Hydrangea germplasm resources， variety identification， and the protection of new plant variety rights in China.【Method】 Fifty species of Hydrangea were used as experimental materials， including 40 species from the Sect. Petalanthae， Sect. Heteromallae， and Sect. Hydrangea groups， as well as 10 representative cultivated varieties of Hydrangea macrophylla. Core primers for SSR molecular markers were screened， and genetic diversity analysis was conducted.【Result】 Six SSR molecular markers were selected that exhibited consistent annealing temperatures， stable amplification， high polymorphism， and uniform distribution across the chromosomes （STAB391-392， STAB321-322a， A029-A030b， STAB167-168， STAB413-414， and STAB421-422）. Among the 50 Hydrangea species tested， the polymorphism information content （PIC） of the six SSR molecular markers ranged from 0.662 to 0.918， with an average of 0.820. The marker with the highest PIC was STAB421-422， with a total of 158 alleles detected， averaging 26.33 per marker； among these， the marker A029-A030b detected the highest number of alleles. The 50 Hydrangea samples were divided into Sect. Petalanthae group， Sect. Heteromallae group， Sect. Hydrangea group， and Hydrangea macrophylla cultivated variety group. GenAlEx 6.5 was used to calculate the genetic similarity coefficients and genetic distances among the four Hydrangea groups. The highest genetic similarity coefficient was observed between Sect. Petalanthae group and Sect. Hydrangea group （0.641）， while the lowest was between Sect. Hydrangea group and the cultivated variety group （0.241）. MEGA 5.0 was used to perform unweighted pair group method with arithmetic mean （UPGMA） cluster analysis， the phylogenetic relationships among the four Hydrangea groups and the phylogenetic relationships among ten Hydrangea macrophylla cultivated varieties were clarified.【Conclusion】 Six SSR molecular markers with high polymorphism and specificity are screened， and an SSR molecular marker system suita-ble for Hydrangea germplasm resources in China has been established， which can successfully identify ten representative Hydrangea macrophylla cultivated varieties.