Genetic Diversity And Parental Analysis Of Seed Orchard Of Larix Prindpis—rupprechtii Mayr

Larix principis-rupprechtii Mayr. is one of the most important conifer species for forestation in north China and seed orchards have been built since1960s. However, lack knowledge of genetic variation after selection among gernerations of seed orchards causes some unclearness in breeding and forestation. Consequently, genetic diversity and pedigree analysis is very important for these seed orchards.The leaf sample is collected in Longtoushan larch seed orchard in Hebei province. The samples are from three generations and analyzed by the technique of SSR molecular markers. The genetic diversity among three generations is analyzed to know whether there is a significant difference after selection. Also parental analysis is carried out based on genotypes as a preparation for further research of pedigree reconstruction. The objective of the study is to understand whether genetic resources would be narrow or different after intensity selection and to what extent the resource should be kept to remain the genetic diversity. The result gained in this study also provides information for promoting a new breeding strategy. The following shows the major results of the study.1. Six EST-SSR primers are selected from114pairs designed for this study and4are chosen from85published SSR primers. In total,10EST-SSR primers are selected to be used in this and other research as they showed good polymorphism and were easy to amplify.2. The result shows that each primer has2-5loci of the population. The numbers of average effective loci for the1st,2nd, and3rd generations are1.92,1.81,2.07and Shannon index are0.7127,0.7052,0.7908. There are no significant differences according to ANOVA analysis.3. Heterozygote is dominant in all three generations as the observed heterozygosity is higher than expected hertozygosity.4. The value of Fst is low, showing that genetic differences are mainly occurred in one generation rather than between generations. It can be concluded that there is no big difference in genetic diversity after selection in the seed orchard by variation analysis.5. Twenty two samples of the first generation (sample amount:50) and16samples of second and third generations (sample amount:40and30) could obtain more than99%of the effective loci of the generation. As a result, not so many natural resources are needed to protect when creating a seed orchard.6. Based on parental analysis, there may be some mistakes about the current pedigree identity in the seed orchard. The most possible parents of15individuals of the2nd generation out of40and3 individuals of the3rd generation out of30are figured out based on parental analysis.