The Research Of Genetic Diversity And The Adaption To The Water In Ulmus Elongata

Ulmus elongata belongs to Ulmus, an endangered and deciduous plant to China which had been listed as state Endangered Plant II. Due to the impact of environmental changes and human activities, the habit of Ulmus elongata became fragmentated. The population size and the number of individuals in the population are gradual reduce. So the research of endangered cause of Ulmus elongata is imminent in order to formulate reasonable and effective protection measures.Our paper studied the genetic diversity and the relationships of Ulmus elongata population with ISSR molecular marker so as to explore the genetic structure and gene flow between populations on the basis of the micro level. And the impact of the environment on the growth of Ulmus elongata was studied in this paper, especially the water stress, for the purpose of revealing the process of adaptation to different environmental conditions and the countermeasures on the basis of the macro level. The main results are as follows:(1) We confirmed the reaction system and reaction procedures that impacted ISSR-PCR reaction by sing factor and orthogonal test.. The amplification procedure was as follows:pre-denaturation at94℃for3min, denaturation at94℃for30s, annealing at a certain temperature30s, extension at72℃for10min with a total of35cycles, saving at4℃after the reaction. And the reaction system was a total volume of25μL, including2.5μl buffer,50ng template DNA,1.2μmol/L primer,0.2mmol/L dNTPs and2.5U Taq DNA polymerase. Taq DNA polymerase was the most significantly impact on the ISSR-PCR than the concentration of primer, and dNTPs was the least impact. We screened out11 primers and their suitable annealing temperature by the the reaction system and procedures for the research of genetic diversity of Ulmus elongata.(2)11primers were used to study the genetic diversity and genetic differentiation of7Ulmus elongata populations. The results showed:Eleven primer combinations produced a total of85unambiguous bands of which70(82.35%) were polymorphic. The percentage of polymorphic loci (PPB) ranged33.33%～100%. At the species level, the genetic diversity was higher, PPB=82.35%,I=0.3959, H=0.2585.While it was lower at the population level, PPB=29.07%,I=0.1733, H=0.1191. The coefficient of genetic differentiation (Gst=0.3682) showed that there has produced significantly genetic differentiation among and within the population of Ulmus elongata. The genetic differentiation among population was less than which within the population. The results of AMOVA proved that. The gene flow (Nm=0.858) demonstrated that there was limited gene flow among populations, which was the most important reason for the genetic differentiation of Ulmus elongata. The seven populations of U. elongata were classified into two groups through cluster analysis. The populations of ZJLA, AHSX and the populations of ZJSY, ZJSC together with the ZJKH, JXWN formed one group, whereas the population in the FJNP is clustered into another group. Mantel test showed a highly remarkable correlation between genetic distance and geographic distance (r=0.7015, P=0.007).(3) The effects of soil water stress on the lipid peroxidation and antioxidant system were studied using1-year-Ulmus elongata seedlings. Seven different levels of drought stress were designed (no stress, mild drought, moderate drought, severe drought, saturation, mild waterlogging and moderate waterlogging). The results showed that the plasma membrane was not synchronous increase apparently, the content of malondialdehyde (MDA) and hydroxyl free radical (·OH) were first decreased then increased at the initial stage. The chlorophyll content and chlorophyll fluorescence were decreased while the pretreatment of the peroxidase (POD) and superoxide dismutase (SOD) activities rose, proline (Pro) and soluble sugar increased to ensure the stability of the membrane system. The increase of NPQ illustrate the proportion of which light energy translated into heat energy was rised. The own defense system of Ulmus elongata can not prevent the damage caused by the reactive oxygen with the sustained water stress. The pretreatment of the peroxidase (POD) and superoxide dismutase (SOD) activities rose began to decline, proline (Pro) and soluble sugar increased. So the plasma membrane, the content of malondialdehyde (MDA) and hydroxyl free radical (·OH) were increased, the chlorophyll content and chlorophyll fluorescence were continued to decline. Fo was rised at the moderate drought and severe drought on the20day, this phenomenon may produce irreversible inactivation. The increase of reactive oxygen species the scavenging exceeded the capacity of cells, leading to the accumulation of reactive oxygen species. The plasma membrane, the content of malondialdehyde (MDA) and hydroxyl free radical (-OH) were lower while the chlorophyll content and chlorophyll fluorescence were higher than the control group at the waterlogging stage, this was due to moist environment was more suitable for the Ulmus elongata growing. Gray statistical analysis showed that chlorophyll fluorescence was apparently affected on the change of soil water, illustrating the photosynthesis of Ulmus elongata seedings was more sensitive to the lack of water, and then SOD. From the results of the present experiment, it was concluded that Ulmus elongata were adapt to waterlogging. Followed by saturation, no stress, mild waterlogging, moderate waterlogging, mild drought, moderate drought and severe drought.