RAPD analysis of genetic diversity of Sargentodoxa cuneata at different altitude and the influence of environmental factors

The genetic diversity within populations and genetic differentiation among populations of Sargentodoxa cuneata at three different altitudes in Tiantai mountain of Zhejiang Province were analyzed by random amplified polymorphic DNA technique. To explore how S. cuneata fits environment, the relationships between the genetic diversity and the environmental factors were analyzed. 13 random primers were selected in the amplification and 88 repetitive loci with 74 polymorphic loci were produced. The total average percentage of polymorphic loci was 84.09%. Among three populations of S. cuneata, the populations at the altitude of 950m showed the most bands and the percentage of polymorphic loci was 39.77%. The percentage of polymorphic loci of the population at the altitude of 730m was 32.95% and took the second place. The population at the altitude of 520m showed the lowest bands and the percentage of polymorphic loci was 31.82%. All of them were distinctively lower than the percentage of total polymorphic loci. Different ecological microhabitat could lead to the difference of the genetic structure. Shannon index of phenotypic diversity shows that the highest genetic diversity occured in the population at the altitude of 950m. The second one occurred in the population at the altitude of 730m and the lowest genetic diversity occured in the population at the altitude of 520m. But the difference between the population at the altitude of 730m and the population at the altitude of 520m was relatively small. The average genetic diversity within populations of S. cuneata accounted for 43.68% of the total genetic diversity while the genetic diversity among populations accounted for 56.32%. All of these show that the genetic variation mainly existed among the populations of S. cuneata. The genetic diversity of S. cuneata estimated with Nei index was lower than that estimated with Shannon index of phenotypic diversity. But the variation trend of the genetic diversity within three populations, as indicated by these two indice, was generally consistent. The genetic differentiation among three populations, as estimated by Nei index, was 0.5406. The distribution of the genetic variation was generally consistent, i.e. the genetic variation among populations was relatively high and that within populations was relatively low. The gene flow estimated from Gst was only 0.4018 and it indicates that gene flow among populations of S. cuneata was relatively low. The genetic identity between the population at the altitude of 950m and the population at the altitude of 730m was the lowest while that between the population at the altitude of 730m and the population at the altitude of 520m was the highest. The genetic distance matrix was calculated using the method published by Nei and the clustering analysis was made using the unweighted pair group method with arithmetic mean (UPGMA). The population at the altitude of 520m clustered with population at the altitude of 730m, and then they clustered with population at the altitude of 950m. The correlation analysis showed that the genetic diversity within populations was significantly positively related with the soil total nitrogen. It indicates that nitrogen was important in the maintenance of the genetic diversity of S. cuneata.