Characterization of genetic structure of Podophyllum hexandrum populations, an endangered medicinal herb of Northwestern Himalaya, using ISSR-PCR markers and its relatedness with podophyllotoxin content

Abstract

To obtain accurate estimates of genetic structure for purpose of conservation planning for wild Indian May apple (Podophyllum hexandrum) in the Northwestern region of Himalayas, Himachal Pradesh, genetic diversity among and within 28 populations were analyzed. Eleven microsatellite DNA markers were isolated and used to quantify genetic structure. Out of 68 ISSR loci tested, 88.23% were polymorphic. The genetic diversity was high (percentage of polymorphic bands, PBB = 83.82%; Shannon’s information index, I = 0.4413) at the population level, but low within individual study populations (PBB = 34.22%; Shannon’s information index I = 0.1879). The mean coefficient of gene differentiation (Gst) was 0.7484, indicating that 29.44% of the genetic diversity resided within the population. Analysis of molecular variance (AMOVA) indicated that 48% of the genetic diversity among the study populations was attributed to geographical location while 29% was attributed to differences in their habitats. An overall value of mean estimated number of gene flow (Nm = 0.1618) indicated that there was limited gene flow among the sampled populations. We found a clear tendency for higher Gst values and podophyllotoxin levels between the populations with increasing geographical altitude. However, the existing variation in podophyllotoxin content among the populations was proved to be coupled with geographical altitude (r = 0.922) but not with genetic variations (r = - 0.273). Hence we recommend that any further cultivation of this species requires optimization of environmental factors in order to increase the rate of production of podophyllotoxin from any collected population.