Population Genetic Diversity And Selection Of Superior Provenances Of Machilus Thunbergii

Machilus thunbergii Sieb. et Zucc., a rare and endangered species of Lauraceae, have excellent characteristics for foresry construction, such as high-grade timber, appreciating landscape effect and salt-tolerance and wind-resisting abilities. In order to reveal the population genetic base of the spceies and the variaion of main growth and ecological traits for the purpose of genetic resource collection and use in future breeding program, the population genetic diversity of M. thunbergii was studied by morphological and molecular marker methods, the seedling growth and salt stress experiments were carried out to evaluate variation of growth and salt tolerance traits between provenances and select superior genetic resources. The main research results are as follows:(1) The phenotypic variation of 9 natural populations of M. thunbergii from China was analized based on fruit, leaf and seed traits. It showes that there are significant difference for most morphological features among and within provenances, with the average coefficient of variation of all phenotypes was 0.154.Latitude, average temperature and frost-free duration are the dominant factors of geographical provenance variation, the northern populations have bigger fruits.(2) The extraction method of high-quality DNA was settled and the stable ISSR-PCR reaction system developed for M. thunbergii. Based on the ISSR marker-aided genetic analysis of 7 natural populations, It showed that the Nei's genetic diversity in provenances was 0.166, Shannon's index was 0.255, the proportion of polymorphic loci was 55.46%, and the genetic diversity level of species(HE=0.229,I=0.363,PPB=98.82%)was higher than that of provenances. Total gene diversity of 7 populations (HT) was 0.2326, and Gene diversity between provenances(Hs) was 0.1656. The genetic differentiation of the species existed mainly within populations(GST=0.288). The populations can be divided into 4 groups based on Nei's genetic distance. (3) The 2-years old seedlings traits were measured with the provenance experiment of 13 seed resources. The seedling height and ground diameter reached very significant difference level among provenances, and the 5 leaf and stem morphological traits also showed marked difference among provenances. The correlations of the traits with geographical climate factors of seed source were not remarkable. The seed sources of Qingdao (Shandong), Zhoushan(Zhejiang), and Hengyang(Hunan) were chosen as the superior ones dued to their fast growth and also better ornamental effects.(4) The variation trends of seedling growth, physiological, root morphological traits under different concentrations and time series salt stress were studies with 6 provenances of M. thunbergii. Along with the phase duration and the increased salt concentration, most of provenances showed the injured symptoms that the permeability of membrane system increased, the oozy rate(relative conductivity,MDA) and proline of leaves rose, the content of chlorophyll A reduced, the root morphology decreased, the net growth of seedling height and ground diameter, average individual biomass reduced. The growth of seedling was inhibited ,and the injury grade ,death number rose after salt stree .It was illustrated that M. thunbergii was hurt, and after salt stress.The plant could rise the content of proline to reduce the extent of salt stress injury.The growth of root of M. thunbergii was influenced after salt stress. The ability of salt tolerance of 6 provenances were sequenced comprehensivly in the method of fuzzy membership function: Qingdao(Shandong) >Zhoushan(Zhejiang) >Wufeng (Hubei) >Hengyang (Hunan) > Lin'an (Zhejiang)> Longnan (Jiangxi). Compared the high tolerant population of Qingdao with the inferior one, Wufeng, it's found the content of Na+/K+ in seedling root was higher than in stem and leaf in Qingdao population,, but it was inverse in Wufeng population, which made clear that the Na+ was more easily transported from roots to leaves under salt stress and hurted the photosynthetic capacity of seedling for Wufeng population so it has a weak salt-tolerance than Qingdao population.