Genetic homogeneity of vegetatively propagated Clinacanthus nutans (Acanthaceae)

Clinacanthus nutans is a medicinal Asian plant often propagated by stem cuttings but little is known about the genetic relationships between existing accessions and the extent of homogeneity. In this study, we examined the genetic homogeneity in 12 C. nutans samples from Malaysia, Thailand and Vietnam reproduced by vegetative propagation from different regions between and within countries, and compared it to sexually propagated Andrographis paniculata (same family), related Clinacanthus siamensis (same family) and an out-group (different family) using restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD) and microsatellite markers. There was a high genetic similarity between C. nutans accessions from all countries, with identical genetic profiles even though they were geographically distant. C. nutans clustered closely with C. siamensis and was distant from A. paniculata and the out-group. Genetic similarity for C. nutans was almost double that of A. paniculata, but the combined clustering analysis revealed higher diversity in C. nutans. These results provide fundamental knowledge in future planting decisions and options, and also facilitate further germplasm conservation of C. nutans and other vegetatively propagated medicinal species.   Key words: Clinacanthus nutans, Andrographis paniculata, Clinacanthus siamensis, Acanthaceae, genetic variation, vegetative propagation, sexual reproduction.