Genetic Diversity Of Provenances Of Betula Platyphylla

Betula platyphylla is very cold-resistant, fast-growing and has a good adaptation to different kinds of environments. It is an extremely important tree species in China. It is widely distributed in China and has diverse variations, but there are very few fine germplasm and but its germplasm resources are in great loss. To protect the fine germplasm resources of B. platyphylla and keep its sustainable genetic improvement, based on the provenance trial in Maoershan Forest Farm of Northeast Forestry University, the genetic diversity of provenances in phenotypic and DNA molecular level were studied in this paper and genetic relations within and among different provenances.1. Genetic variation of phenotypic traits4 phenotypic traits (DBH, tree height, stem volume and cellulose content) of 16 provenances were analyzed, and results show that there is abundant variation in each trait among different provenances. The variation coefficient of stem volume is the biggest (37.01%) and that of tree height is the smallest (13.42%). There is also large variation within each provenance in the 4 traits. The average variation coefficient of 4 traits of Xinjiang provenance is the biggest (26.07%), and that of Dongfanghong provenance is the smallest (18.31%).2. Comprehensive evaluation on phenotypic traits of different provenancesVariance analysis shows that there are significant differences among the provenances in each trait. Multiple comparison and principal component analysis indicate that Maoershan, Dongfanghong and Wuyiling provenances are the best in 4 traits. Moerdaoga, Chuoer and Ningxia provenances are the worst. Other provenances are intermediate, including Wangqing, Huinan, Lushuihe, Changbaishan, Xiaobeihu, Liangshui and Xinjiang.3. geographic variation law of B.platyphylla provenancesThe canonical correlation analysis between phenotypic traits of B. platyphylla and geographical climatic factors of the different provenances shows that the geographic variation is mainly caused by latitude and temperature and sunlight are the primary influential factors affecting phenotypic traits, which generally conforms to the research results of geographic variation of Betula platyphylla at'seedling age previously.4. Genetic variation in DNA molecular level300 DNA individuals were amplified with 18 highly polymorphic ISSR primers. Totally 127 loci are detected and an average of 7.05 bandings are amplified with one primer. There are 124 polymorphic loci and the percentage of polymorphic loci is as high as 97.64%. The range of the percentages of polymorphic loci of 15 provenances is 48.03%～62.20%. The total gene diversity (Ht) of all provenances is 0.3438 and the gene diversity within provenances (Hs) is 0.1892.55.03% of the genetic variation of Betula platyphylla is within provenances and 44.97% is among provenances.300 DNA individuals were amplified with 15 highly polymorphic RAPD primers. Totally 188 loci are detected and an average of 12.3 bandings are amplified with one primer. There are 185 polymorphic loci and the percentage of polymorphic loci is as high as 98.40%. The range of the percentages of polymorphic loci of 15 provenances is 58.6%～77.96%. The total gene diversity (Ht) of all provenances is 0.2531 and the gene diversity within provenances (Hs) is 0.2030.80.21% of the genetic variation of Betula platyphylla is within provenances and 19.79% is among provenances.The range of genetic identity among different provenances based on ISSR analysis is 0.6470～0.9709, and the range of genetic distance is 0.0295～0.4354. The range of genetic identity among different provenances based on RAPD analysis is 0.9007～0.9681, and the range of genetic distance is 0.0324～0.1046. As the theories of ISSR and RAPD are different which reveal different scope of genomic DNA, different genetic identity and genetic distance are obtained.4 provenance groups are divided for 15 provenances based on the cluster dendrograms drawn by 2 markers. Although the 2 cluster dendrograms are not exactly the same, there is still much similarity between them.5. Comparison of analysis by different markersCorrelation analysis was done with the genetic parameters of different markers and results show that there is no significant correlation among different markers. For the detecting ability on the genetic diversity of B. platyphylla of RAPD is higher, the gene locus detected by RAPD is more randomly and the cost of RAPD is lower, so it can be thought that RAPD is more reliable in detecting the genetic diversity of B. platyphylla. In practice, the most appropriate marker and analysis can be selected according to the correlation between the the traits which are to be improved and different markers.This study shows that the results of genetic diversity obtained by different markers are different, so it is necessary to study the genetic diversity of forest trees with different markers. This study has revealed different variations and affiliations of provenances and provided theoretical basis for using the genetic resources of B. platyphylla wisely and efficiently.