Regeneration And Preliminary Evaluation Of Genetic Diversity In Disturbed Populations Of Houpo(?)a Officinalis

Houpo?a officinalis belongs to Genus Houpo?a,Family Magnoliaceae,an endangered and deciduous plant to China.It is listed as state Endnagered Plant ?.It is a medicinal plant that widely distributed in subtropical and north tropical regions alongwith the Yangtze River,the bark,root bark,flowers and leaves of which can be used as medicine.Due to a wide range clinical use of H.officinalis,the market demand keeps increasing,and wild resources have drastically decreased under uncontrolled exploitation.Habitat of H.officinalis has become fragmentated.Habitat fragmentation blocks gene exchange among natural populations,and the survival situation is becoming more serious.Thus,it is an urge to carry genetic diversity restoration and wild resources conservation for H.officinalis.In this study,wild populations and cultivated groups were used as the research object to investigate the seed bank,dynamics of seed feeding by the animals,the germination and seedling growth of H.officinalis.Obstacle factors of natural regeneration were also analyzed.The sampling strategy and technical measures for H.officinalis reintroduced protection are formulated based on the analysis of genetic diversity in wild populations with inter-simple sequence repeat(SSR)technique.According to the sampling strategy,the reintroduced population of H.officinalis was established in the affected group,and the adaptability was aslo evaluated,which provide theoretical basis and practical guidance for the protection of endangered plants.The main results are as follows:1)The vertical distribution characteristics of H.officinalis seeds in the soil showed that the litter layer was larger than 0~2 cm and the soil was larger than 2~4 cm soil layer.As the soil layer deepened,the number of seeds gradually decreased.The seeds in the H.officinalis soil seed bank accounted for 67.22% of the total,and the number of intact seeds is very low,accounting for 18.48%.All seeds with bare surface were eaten in situ by rodents within 12 days,litter cover and iron-box cover had a certain protective effect on seeds.In the three habitats,the seeds feeding rate in the roadside and the open space were higher than those in the forest bushes.Cross-treatments of the seed coat(removing or preserving the aril)and the wire mesh(cover or not cover)were taken to reveal seed germination and seedling growth characteristics of H.officinalis in different habitats.Superiority of seedling height and ground diameter of H.officinalis in coniferous forest were better than those in coniferous and broad-leaved mixed forest,and superiority of H.officinalis in coniferous and broad-leaved mixed forest were better than those in broad-leaved forest.The aril,animal feeding and habitat heterogeneity are three main reasons that led to low germination rate and high mortality of H.officinalis bark seeds.In terms of the protection of H.officinalis,there is a need to strengthen the restoration of fragmentation habitats,establish an ecological environment suitable for the growth of magnolia,and implement appropriate manual management to reduce animal predation,improve seed germination and promote healthy growth of seedlings.2)Besed on 10 pairs of SSR primers with rich polymorphism,stability,and high repeatability,the genetic diversity of 9 natural populations of H.officinalis was analyzed,computer was used to simulate the sampling.Results showed that the natural population allele could be retained more than 95% when 6 populations to the sampled and the sampling proportion were 30%.The genetic diversity analysis of H.officinalis seedlings(8 provenances)in the reintroduced population showed that the genetic diversity was high(I=1.186,Ne=3.563,He=0.620),the genetic variation was mostly found in the population and there was a certain degree of genetic differentiation.3)The adaptability of 8 H.officinalis species in 2 locations of reintroduction was evaluated in this study.Botanical characteristics including plant morphology and growth situation were observed and principal component analysis and gray-correlatiion analysis was used to evaluate the seedlings adaptability of reintroduction.The result showed that adaptability is different between provenances anddestination area for reintroduction.The high annual growth and ground diameter of seedlings in the NO.1 habitats for reintroduction were more than NO.2 habitats.Significant differences were observed in seedling height and ground diameter growth of seedlings from various sources(P<0.05).In addition,local seedlings were the best when comparing to other provenances in the 2 habitats for reintroduction.The diseases and insect pests showed different performance at different periods.In June and July,diseases and insect pests reached the peak.The disease and insect pests of the seedlings in NO.1 habitats for reintroduction were significantly lower than that in NO.2.Hybrid seedlings had the slightest pests and diseases,which means that they are more resistant to insects through hybrid seedlings.More than 70% of seedlings survived in the reintroduced population of H.officinalis.Gray correlation analysis showed that the correlation coefficient of 8 Houpo?a officinalisspecies with the ideal species from high to low were Suichang,Panan,Anji,Guangze,Hybird seedling,Lushan,Jianning and Tonggu.The correlation coefficients of H.officinalis seedling in the process of reintroduction to the ideal species was 0.795,indicating that the reestablished population of H.officinalis was initially successful.The correlation coefficients of two habitats for reintroduction to the ideal species were 0.774(Panan)and 0.815(Suichang).Regression of the introduction material and the habitats for reintroduction might be key factors affecting the reintroduced protection of H.officinalis.