Studies On Mating System Of Camellia Tunghinensis Based On SSR Markers And Its Drought Resistance

Camellia tunghinensis Chang is the evergreen shrubs or small trees of Theaceae, Camellia, Sect. Chrysantha Chang. Its distribution range is very narrow and its wild resources are very few. In recent decades, due to the deforestation and destructive collection of seedlings, its natural population size has declined greatly and its resources are on the verge of extinction, so it needs to be protected urgently by our human beings. In order to provide reference basis for the protection and cultivation of C. tunghinensis, mating system of C. tunghinensis was analyzed by SSR markers, and its drought resistance and flower bud differentiation were also studied. The main results are as follows.1. In order to provide basic genetic information for the conservation, SSR markers were used to investigate the genetic diversity and structure of4natural populations and progeny populations of C. tunghinensis. At the population level, each natural population of C. tunghinensis polymorphism percentage group the (P) was100%; the number of effective alleles was3.203-3.821, and the average value was3.652; Shaonnon diversity index (I) was1.274-1.455with the average value1.351; the observed heterozygosity of Ho was0.807-0.867, and the average was0.830; the unbiased expected heterozygosity uHe was0.677-0.739with the average value0.707; Nei’s diversity index of expected heterozygosity He was0.648-0.716, and the average value was0.681; the population polymorphism site of Wright fixation index F was between-0.305and0.159, with an average of-0.223, which showed that the heterozygote excess phenomenon was existed in various populations of C. tunghinensis Chang; through Bonferroni correction after the5%level, the MJG、DLG、MZT populations were significantly deviated from Hardy Weinberg equilibrium. The genetic variation of C. tunghinensis mainly exists in populations inside.At the population level, progeny population of C. tunghinensis polymorphism percentage group (P) was100%; the number of effective alleles was3.230-4.516with the average value3.598; Shaonnon diversity index (Ⅰ) was1.290-1.551, and the average value was1.433; the observed heterozygosity of Ho was between0.819and0.868, and the average value was0.845; the unbiased expected heterozygosity uHe was0.677-0.739, and the average was0.707; Nei’s diversity index of expected heterozygosity He was0.659-0.734with the average value0.698; the fixation index F was between-0.332and0.157, with an average of-0.212; through Bonferroni correction after the5%level, the MJG、SHI、DLG、MZT populations were significantly deviated from Hardy Weinberg equilibrium.2. Mating system of C. tunghinensis was analyzed by8pairs of SSR markers.5populations of tm values were1.002(MZT),1.008(ZWS),0.939(MJG),0.975(DLG),0.938(SHL), and its order of magnitude was the MZT>ZWS>MJG>DLG>SHL; the Ts value of MZT was0.981, ZWS was0.958, MJG was0.741, DLG was1.030, SHL was0.809, and the size of the order was MJG>ZWS>MZT>DLG>SHL; the population multilocus outcrossing rate and single locus outcrossing rate of the5populations were at a relatively high level. The rpm value of5populations, between0.003and0.227, were relatively small, which indicated that the parents of sub generation with the sister relationship in the same population were less, and the occurrence rate of inbreeding were also lower. The maximum rt values of the5populations were ZWS and MZT, which indicated that the degree of variation of5populations were relatively large. The sub structure might be existed in the5populations, because of the greatly varied values between the rt and rpm values.The F value of the5populations was less than0, except for the ZWS populations, might because the homozygous excess phenomenon existed in ZWS populations, the heterozygote excess phenomenon were in the other4populations. Mating system of C tunghinensis was mixed with selfting and outcrossing, outcrossing mainly supplement with selfting.3. Using paraffin method, the flower bud differentiation process of C. tunghinensis were divided into6stages:undifferentiation period, initial stage, sepal differentiation phase, petal differentiation stage, stamen differentiation stage and pistil differentiation phase. There was an overlapping phenomenon between two periods.4. Drought stresses had important effects on physiological and ecological indexes of C.tunghinensis, including soil moisture rate, the relative water content of leaves, MDA content, photosynthesis, photo synthetic pigment and fluorescent pigment. Compared with the control group, soil moisture of group CL1decreased by17.691%, suffering from slight drought stress; group CL2decreased by43.209%, group CL3by46.632%, suffering from moderate drought; group CL4decreased by56.752%, encountering severe drought stress. Compared with the control group, the relative water content of leaves decreased significantly. Groups CL1, CL2, CL3and CL4were decreased by3.895%,22.626%,31.557%,45.752%, respectively. Compared with the control group, the MDA content of group CL1, CL2and CL3changed insignificantly under drought stresses, but that of group CL4increased significantly by40%from0.02883to0.04035. Compared with the control group, photosynthetic rate of group CL1、CL2、CL3and CL4decreased by7.709%,30.617%,59.472%,89.648%, the stomata conductance decreased by10%,34%,62%,80%, and the transpiration rate decreased by14.235%,36.588%,63.176%,82.824%, respectively. The contents of chlorophyll a (Ch1a), chlorophyll b (Ch1b) and carotenoid (Car) in leaves all decreased significantly with the intensification of drought stresses. F0decreased significantly indicated that PS Ⅱ reaction center was seriously destroyed; Fm and Fv increased firstly and then decreased; no significantly difference was appeared in F0, but decreased significantly at the significant level (p<0.05).