Differential morphogenetic responses, ginsenoside metabolism and RAPD patterns of three Panax species

Abstract

Genetic and metabolomic demarcations between two Indian and one American congeners of Genus Panax have been discerned. Genomic DNA was isolated from the root derived callus cultures of these species and amplified by AP-PCR. RAPD analyses of the DNA with six most responding arbitrary oligonucleotide decamers provided a total of 70 reproducible bands for computation of the similarity matrix amongst the Panax species. Only 18 of these were monomorphic giving an estimate of about 74% polymorphism among the test species examined. The similarity coefficient values based on the amplification pattern support an equidistant position of the three test species. The molecular demarcations between the species are also manifested in terms of their characteristic cultural requirements, in vitro growth kinetics, regeneration competence and ginsenoside complement of their calli. The Indian congeners i.e. P. sikkimensis and P. pseudoginseng were distinguishable by higher proportions of ginsenoside Rf and Ro (40% and 20%, respectively) in the crude saponin fractions. Furthermore P. quinquefolium calli mainly accumulated ginsenoside Rb₂ and Rg₁, whilst P. sikkimensis callus was rich in Rd fraction. P. quinquefolium showed high similarity with P. sikkimensis with respect to plasticity and totipotency for somatic embryogeny whereas P. pseudoginseng callus was highly recalcitrant and lacked regenerative capacity. The chemical and genetic fingerprints alongwith morphogenetic responses of the three species under controlled in vitro environment strongly advance the case of P. sikkimensis as an independent species, rather than a conglomerate of location specific variety or sub-species of P. pseudoginseng. The findings are also of relevance to formulations and evaluation of ginseng-based health foods.