Keywords: 
• botany /
• Rhododendron hybridum /
• genetic diversity /
• SRAP-PCR /
• orthogonal design /
• system optimization /
• cluster analysis

Abstract: In order to find the optimal sequence-related amplified polymorphism（SRAP）-PCR system of Rhododendron hybridum and analyse its genetic diversity，the functional leaves of Rhododendron hybridum were used to extract its genome DNA，using an improved cetyl trimethyl ammonium bromide（CTAB）method. Concentrations of Mg2+，Taq polymerase，dNTPs and primer, which maybe affect the SRAP-PCR reactions，were optimized by L16（44）orthogonal design experiments to establish the SRAP molecular marker system in Rhododendron hybridum. Then，an optimal, stable and repeatable SRAP-polymerase chain reaction（PCR）of 20.0 L containing 1.750 mmolL－1 Mg2+，0.175 mmolL－1 dNTPs，1.500 16.67 nkat Taq polymerase，and 0.200 molL－1 primer was established. Finally， genetic diversity and relationships of 24 Rhododendron hybridum cultivars were analyzed using an Unweighted Pair Group Method with Arithmetic Mean（UPGMA）cluster analysis with this optimized system. Results revealed 10 highly polymorphic and stable primer pairs selected from 88 pairs of SRAP primers with a total of 217 bands being detected from these 10 primer pairs. Of the detected bands，212 were polymorphic（a 97.35% average）having a genetic similarity coefficient ranging from 0.591 to 0.708. The cluster analysis divided the 24 cultivars into two groups at a 0.590 similarity level，and these were further delineated into two sub-groups at a 0.623 similarity level. These results demonstrated that this optimized SRAP-PCR system can be applied to cultivars identification and genetic diversity research on Rhododendron hybridum.［Ch，3 fig. 6 tab. 19 ref.］