Genetic diversity of 129 spring orchid (Cymbidium goeringii) cultivars and its relationship to horticultural types as assessed by EST-SSR markers

• The existing taxonomy of the nine recognized variants is not genetically supported.
• Sub-grouping of spring orchid was not related to the horticultural types.
• Specific alleles could be identified for many cultivars using specific primer pairs.
• The data provided information for further taxonomy and horticultural studies as well as useful EST-SSR markers for cultivar identification.

Spring orchid (Cymbidium goeringii), a valuable and endangered species in China, plays an important role as a potted flower. The genetic diversity of 129 spring orchid cultivars was evaluated with 13 selected EST-SSR markers and 120 alleles were identified, of which 111 alleles were polymorphic. The plum petal type, with 43 cultivars, contributed 102 polymorphic alleles out of the 111, while the colored flower type, with 3 cultivars, had 38 polymorphic alleles. Cluster analysis showed that these 129 spring orchid cultivars could be sorted into two groups, or three subgroups (A1, A2, B), based on the allelic data, and with all cultivars from three currently recognized variants intermingled with some cultivars from C. goeringii in the same subgroup, indicating that they should not be regarded as variants. Through principal coordinate analysis, only a weak correlation between DNA fingerprints and the horticultural types of the spring orchid was observed. However, common alleles existed in cultivars from the same horticultural type, for example, 15 common alleles were found in the 3 cultivars of the colored flower type, and the CY2-J allele existed in the 43 cultivars of the plum petal type. All these cultivars, except for Longzi and Lao Longzi, could be distinguished from each other using these EST-SSR markers. Moreover, a set of 102 out of the 129 cultivars had their own specific alleles, and therefore, with a single EST-SSR marker, each of these cultivars can be distinguished from all other cultivars. These findings can be valuable for taxonomy improvement as well as resource conservation and utilization, and the EST-SSR markers developed can also be a useful tool for cultivar identification which is frequently required commercially.