Allozymic Variation and Genetic Relationship among Gastrodia elata Forms,a Medicinal Plant in China

Gastrodia elata(Orchidaceae),a rare and endangered medicinal plant,is a polymorphic species with more than six forms.Allozymic variation of four form in G.elata from Hubei provinces was analyzed using isoelectric focusing in thin-layer polyacrylamide slab gels.Thirty-seven alleles of 17 loci in six enzyme systems were examined,in which 11 loci were polymorphic.The maximum number of alleles in a locus was four.Form specificity was found in alleles of loci Acp-4 and Prx-2.A high genetic diversity was observed at species level with mean number of alleles per locus A=2.1,mean percentage of polymorphic loci P=56.3% and average expected heterozygosity H_e=0.222,while a lower genetic diversity was found at form level(P=42.2%,A=1.7,H_e=0.146).Among the four forms investigated,the highest level of genetic variation was found in G.elata f.glauca(P=50.0%,A=2.1,H_e=0.184),and the lowest in an unidentified G.elata form named as’Yao Tianma’ by local farmers(P=25.0%,A=1.4,H_e=0.093).A high genetic differentiation among different forms was revealed(G_ST=0.3595),which may be due to restricted gene flow among forms(N_m=0.445).Cluster analysis using UPGMA based on Nei’s genetic distances revealed that populations from the same form tended to cluster together,suggesting that each form of G.elata was an indepen-dent evolutionarily significant unit in genetics,and the intra-species subdivision of G.elata are well supported by the present study.Results of this study also revealed that G.elata f.elata had a closest genetic relationship with G.elata f.glauca,while the unidentified form ’Yao Tianma’ is closest to another unidentified form named ’Huo Tianma’.