Application of RAPD markers for evaluation of genetic diversity in Spiranther sinensis and S. hongkongensis (Orchidaceae)

Abstract

In Hong Kong, urban development has rapidly encroached on many diverse natural habitats, which once supported more than one hundred species of wild orchids such as Spiranthes sinensis and S. hongkongensis. To estimate and conserve the existing genetic diversity in the wild orchids, the random amplified polymorphic DNA (RAPD) method was used for analyzing genetic diversity. A total of 329 distinct DNA fragments were amplified using 33 random ten-base synthetic oligonucleotides. The proportion of polymorphic loci was 64% in Spiranthes sinensis, and 17% in S. hongkongensis. The RAPD data is consistent with isozyme analysis, which revealed a very high level of genetic variation in populations of S. sinensis (P = 44.8%, A = 1.65, H = 0.17), but nearly complete lack of isozyme variation in populations of S. hongkongensis. Factors that may have contributed to this contrasting pattern of genetic diversity in the two species, and implications for orchid conservation, will be discussed