Genetic Diversity Evaluation And Genetic Linkage Map Construction Of Dendrobium Officinale

Dendrobium species are the traditional precious Chinese medical herbals. They are distributed in tropical and subtropical Asia and North-Australia, with distinctive genetic diversification. Most plants of the genus Dendrobium have wide and effective usage in traditional medicine and flower horticulture. As the main representative medicinal species in Dendrobium genus, Dendrobium officinale is one of the most precious Chinese herbal medicines in China. In the2010edition of the "People's Republic of China Pharmacopoeia ", Dendrobium officinale is stated alone apart from the other medicinal Dendrobium species. With the development of its industrialization, people pay more attention to the research and development of D. officinale. But up to now, genetic diversity and the genetic maps of D. officinale have been ralely reported at home and abroad.On the basis of the morphological character of D. officinale, SSR was applied to evaluate genetic diversity and phylogenetic relationship among19D. officinale materials. In total,142bands were amplified by34SSR primers from309pairs SSR primers in Dendrobium species. On average, each primer contained5.81bands, and the polymorphism locis were122, with60%to100%polymorphism. The average polymorphism ratio was86.5%. UPGMA results showed that19D. officinale materials were grouped into two clusters with a similarity level of0.53. The genetic similarities calculated from simple matching model among19materials ranged from0.35(number2/number3) to0.82(number6/number19).We selected Dendrobium. officinale from Jinhua, Zhejiang as the female parent from19germplasm of D. officinale, and Dendrobium. aduncum from Luxi, Yunnan as male parent. An integrated genetic linkage map was constructed by the F1population with140individuals derived from an interspecific cross between two Dendobium species (D. officinale,2n=38and D. aduncum,2n=38) using simple sequence repeats (SSR) markers and Sequence related amplified polymorphism (SRAP). A total of261SRAP markers and88SSR markers were identified and used for genetic linkage analysis. JoinMap4.0and MapDraw V2.1software were used to construct their genetic maps based on the polymorphic loci data tested from the segregating population. For the map,157loci were arranged into27major linkage groups (LGs), each containing a minimum of four markers, and a further23markers were distributed to5triplets and4doublets. The map covered a total distance of1580.4cM, the average distance of the map being11.89cM between adjacent markers. The length of the linkage groups ranged from6.6to176.9cM, and the number of markers per group varied from4to14. Linkage group D1contained the largest number of markers (14), whereas LGs D11, D12, D13, D14, D16, D17, D18, D24, D25and D26had the least, with only4markers each. On average, each LG contained5.81markers. The longest gap of33.7cM was found on LG D5.This study provided a molecular means to define the geographical origin of the D. officinale germplasm resources, to establish the fingerprint system of D. officinale, to identify and eliminate the adulteration of D. officinale and to ensure herbs authentic and pharmacodynamics of the D. officinale. This primary map provided an important basis for the genetic study of Dendobiumgenus, making it possible to enhance the density and precision of the map in future study, and to apply a marker-assisted selection breeding strategy in D. officinale.