Genetic Diversity And Genetic Structure Of Larix Chinensis Beissn.by AFLP Analysis

Larix chinensis Beissn., an endemic species to China, belongs to the genus Larix Milland only distributes on several peaks of Qinling Mountains in Shaanxi Province. It hadbeen listed as second grade plant species of state in need of conservation.L. chinensis is very important water-nurturing forest located in the top of the forest inMt. Qingling. And it also has the significant significance for the conservation of waterand soil, the stable stone, the ecological environment improvement. So it has theconservative and research value on the respect species conservation scientific research,ecology and economy.Though there have been some studies of the genetic diversity of L. chinensis, thereare also some questions need to study. Such as, the percentages of polymorphism, thenumber of migrants per generation and the results of UPGMA dendrogram are verydifferent in the former studies. As the largest and the best growing population of L.chinensis, Taibaishan population needs more thorough research. The L. chinensis hashad the remarkable change along with elevation elevating in the morphology, its geneticdiversity also has had whether the change. These questions all wait for the further study.This paper, using AFLP as the molecular maker technique, mainly deals with geneticstructure and genetic diversity in the three populations of Guangtoushan, Niubeiliangand Taibaishan, especially the study of the Taibaishan population.(1)Using eight pairs primer combinations, 58 individuals from three populations wereanalyzed with AFLP. The results indicate that the whole number of bands is 26509; theaverage number of each individual is 457; the average number of each primercombination is 3314. The bands mainly distributed among 70-300bp and the smaller ofbands, the larger of the number of the bands.The study shows that the results is very different if the different selection of length ofbands.(2)The results of the different methods of RAPD, SSR, ALLOZYME and AFLPindicate the sites of the number of polymorphic bands, the percentage of polymorphism,Shannon diversity index, UPGMA dendrogram based on Nei's (1978) genetic distanceare very different. But the whole genetic diversity and genetic structure are identical. The genetic diversity is high and the most genetic diversity is within population.(3)Using eitht pairs primer combinations, 58 individuals from three populations wereanalyzed with AFLP. 1728 bands were detected, and there were 1123 polymorphicbands among them. The numbers of polymorphic bands are respectively 688, 615, 1035in the Guangtoushan, Niubeiliang and Taibaishan population. The percentages ofpolymorphism are 64.99% at species level. As a local species, L. chinensis has a highergenetic diversity.Observed number of alleles and effective number of alleles are respectively 1.9878and 1.2553 at species level. Shannon diversity index is 0.2448 at species level. Thepartitioning of the diversity (Shannon's index) within and between populations of L.chinensis for eight primer combinations are respectively 0.2012 and 0.8219.Nei's indexis 0.1498 at species level of L. chinensis and within populations of Nei's index is 0.1310.The coefficient of gene differentiation is 0.1236. It shows that the most diversity arewithin populations.The number of migrants per generation is 3.7572. Theoretically, Nm is enough toresist the effect of genetic drift and prevent population from subdivision.The Nei (1978) genetic identity and genetic distance show that genetic identityamong population of L. Chinesis is very high with a mean of 0.9737, and the mean ofgenetic distance is 0.02677. They show that high genetic similarity was found amongpopulation of L. Chinesis. Dendrogram resulting from UPGMA method clusteringbased on Nei (1978) genetic distance shows that the Guangtoushan and Niubeiliangpopulation has higher similarity. This is identical with the geography distance of thepopulations.(4)Analysis of the different altitude (＜3200m, 3200m-3300m, 3300m-3400m and＞3400m) of L. Chinesis in the Taibaishan population shows that this species changedlittle with the change of the altitude.In short, the result of this study shows that Larix chinesis Beissn. has a higher geneticdiversity, and it is most within populations. The population of Taibaishan has the highestdiversity and requires that priority is protected.