Genetic variability and association of AFLP markers with some important biochemical traits in Dendrobium thyrsiflorum, a threatened medicinal orchid

Abstract

Orchids have been used traditionally in various herbal preparations of which Dendrobium thyrsiflorum deserves special mention. However, in spite of being such an important medicinal plant taxa, information on the genetic diversity of the orchids is limited. In order to establish an association with antioxidant activity of D. thyrsiflorum, five geographically distinct populations of D. thyrsiflorum were analyzed. Total phenolics, flavonoids and alkaloid contents along with antioxidant activity measured by 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays revealed a significant level of variability across populations. Higher phytochemical activity was recorded in the representatives from Sikkim as compared to those from Mizoram. The genetic information obtained from fifty genotypes sampled from five natural populations using nine AFLP markers exhibited a total of 1207 scorable peaks of which 1188 peaks were polymorphic with high genetic diversity [percentage polymorphic bands (PPB)-98.50%; Shannon's index (I)- 0.42 and Nei's Gene Diversity index (h)=0.28]. Analysis of Molecular Variance (AMOVA) revealed that variation amongst the populations was significantly higher than within the populations. Both UPGMA and STRUCTURE analyses were employed to estimate the genetic relationships of D. thyrsiflorum germplasm. Interestingly, both methods revealed similar grouping patterns. Further, statistical analysis of molecular data revealed that four out of these nine AFLP markers tested were found to be correlated with the antioxidant activity measured by DPPH assay. With no available genetic information like linkage maps and Quantative trait loci (QTL) available, the present research finding can be utilized for conservation strategy formulation of this important medicinal orchid with high antioxidant activity.