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Spring orchid (Cymbidium goeringii) is a popular flowering plant species. There have been few molecular studies of the genetic diversity and conservation genetics on this species. An assessment of the level of genetic diversity in cultivated spring orchid would facilitate development of the future germplasm conservation for cultivar improvement. In the present study, DNA markers of intersimple sequence repeats (ISSR) were identified and the ISSR fingerprinting technique was used to evaluate genetic diversity in C. goeringii cultivars. Twenty-five ISSR primers were selected to produce a total of 224 ISSR loci for evaluation of the genetic diversity. A wide genetic variation was found in the 50 tested cultivars with Nei's gene diversity (H = 0.2241) and 93.75% of polymorphic loci. Fifty cultivars were unequivocally distinguished based on ISSR fingerprinting. Cultivar-specific ISSR markers were identified in seven of 50 tested cultivars. Unweighted pair-group mean analysis (UPGMA) and principal coordinates analysis (PCA) grouped them into two clusters: one composed the cultivars mainly from Japan, and the other contained three major subclusters mainly from China. Two Chinese subclusters were generally consistent with horticultural classification, and the third Chinese subcluster contained cultivars from various horticultural groups. Our results suggest that the ISSR technique provides a powerful tool for cultivar identification and establishment of genetic relationships of cultivars in C. goeringii.

ISSR was applied to detect the relationship between 16 Cymbidium species, and 836 bands were amplified with 15 primers, including 227 polymorphic bands. The polymorphic percentage is 27.2%. UPGMA results showed that the genetic distance were closest between C.goeringii (Rchb.f.) Rchb.f. and C. goeringii var. longibracteatum, and C.lancifolium Hook. was far away from the other 15 species. This result is quite similar to the traditional classification, indicating that the technique could supplement some information to traditional taxonomy in the molecular level.

The techniques of random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphisms (AFLPs) were used to amplify the genomic DNA of 10 species of Ilex, so as to reveal the polymorphism in different species of Ilex. In RAPD analysis, a total of 301 lines were amplified with 11 kinds of primers selected from 100 kinds of 10 bp random primers, and the polymorphism was 98.63%. In AFLPs analysis,a huge diversity was showed by 3 primers combinations carried out on these species. Both RAPD and AFLPs analysis were clustered by UPGMA and the results showed that the genetic distances were the closest between I. purpurea and I. vomitoria Ait, I. Litseaefolia and I. zhejiangensis, I. hylonoma var. glabra and I. triflora var. kanehirai.

Amplified fragment length polymorphism (AFLP) was assessed in 13 Chinese species of Dendrobium. Three primer combinations E+ACT/M+CAC, E+AAC/M+CAC and E+ACA/M+CAC were used for selective amplification. Between 100 bp and 300 bp, a totle of 346 fragments were detected, in which 342 are polymorphic. The rate of polymorphism was 98.8%. The AFLP data were analyzed using Nei & Li similarity coefficient and UPGMA Cluster method. The result indicated that the 13 species were clustered into three groups on coefficient level 0.54. Group I included D. falconeri, D. officinale, D. wilsonii, D. hercoglossum, D. crystallinum. D. hancockii, D. guangxiense, D. primulinum, D. crepidatum, D. thyrsiflorum. Group II included D. chrysotoxum. Group III included D. loddigesii. This outcome was corresponding to the classification result by using the traditional method. It is concluded that AFLP markers can be used on the studies of genetic relationships and classification of Dendrobium.

RAPDs and AFLPs were used to investigate the genetic variation of 14 species of Cymbidium. A great diversity was shown by 12 random primers and three primer combinations. UPGMA cluster analysis showed that the results from the RAPD and AFLP analysis were similar and the genetic distances were closest between C. ensifolium and C. sinense, C. kanran and C. faberi var. omeiense, C. mastersii and C. eburneum respectively.