A Study On Genetic Diversity Of Thellungiella Salsuginea Among And Within Populations

Thellungiella salsuginea, belonging to Thellungiella of Cruciferae, is an annual herb. It is a close relative of Arabidopsis. Study showed that 300mM NaCl was a salinity threshold for salt cress growth which decreased the survival rate by 50% relative to the medium without salt, 100-150mM NaCl was the optimum growth salinity for salt cress. As we know, a model plant would be needed that had desirablelife history traits, i.e. small size, short life cycle, self-pollination, and high seed number, and favorablegenetic traits such as self-fertilization, a small genome, efficient transformation, and mutagenesis. One halophytic plant species that meets all of these criteria is Thellungiella salsuginea.Few reports concern research about Thellungiella salsuginea. In the paper, we have collected 7 populations of Thellungiella salsuginea in China, and we have studied the genetic diversity of the populations by means of morphology, micromorphology and RAPD.We have studied the genetic diversity of 7 Thellungiella salsuginea populations in China by means of leaf morphology and seed micromorphology, pollen micromorphology. Study on morphology and micromorphology shows that there are some differentiations among Thellungiella salsuginea populations, especially between Xinjiang population and DongYing population, while there are few differentiations among other populations. So we don't conclude that morphology study can distinguish the 7 populations completely, and we must carry on further more research by means of molecular markers.The genetic diversity of Thellungiella salsuginea populations was investigated by random amplified polymorphic DNA(RAPD). 40 primers were chosen for amplification among populations because they showed strong, reproducible amplification and distinct polymorphisms from over 400 10-base arbitrary primers, and 20 primers were also chosen for amplification within populations. A total of 351 DNA fragments were amplified from 300 ~ 2500bp among populations, among which 279 were polymorphics. and constituted 79.49%. The average number of DNA bands produced by each primer were8.78. The Jaccard coefficient and distance based on it was worked out by NTSYS-pc software, and then we compute the euclidean distance. The result of distance based on Jaccard coefficient for 7 Thellungiella salsnginea populations ranged from 0.265 to 0. 644 and the euclidean distance ranged from 7.1 to 10. 5. Result showed that Thellungiella salsuginea possessed a higher genetic diversity among population. A DNA molecular dendrogram was established for 7 Thellungiella salsuginea populations based on UPGMA(Unwighted pair-group method with arithmetic mean ). According to the result, the differentiation between DongYing population and Xinjiang Population is the hightest, while the differentiation between DongYing population and QiHe Population is the lowest.RAPD analysis was also performed within Thellungiella salsuginea populations. The percentage of polymorphic loci, Shannon Index and euclidean distance was computed. From those we can suggested that Thellungiella salsuginea possessed a lowergenetic diversity within populations. For DongYing population, the percentage of polymorphic loci reached 62.4%,Shannon Index arrived at 0.4040; while 39.5% and 0.3054 for Xinjiang population. The trend of euclidean distance was familiar with the percentage of polymorphic loci and Shannon Index.In summary, Thellungiella salsuginea was rich in genetic diversity among populations, and there was a higher genetic diversity among populations than within populations. Different environment caused the differentiation of Thellungiella salsuginea populations.