| Prunus triloba is a deciduous and flowering shrub or small tree species, which belongs to Prunus of Rosaceae. Prunus triloba is a famous ornamental plant in China, and mainly distributed in the Northeast and North China. Having various kinds of varieties and long history of cultivation, Prunus triloba has been widely used in landscape as an important early spring flowering ornamental in Northern China. However, few researchers have ever studied its wild resources systematically. Prunus triloba is octaploid (2n=8x=64), distributed in slopes, valleys or forest edges in middle elevation areas. There are many variation types of Prunus triloba, since it has strong adaptability to environment and great natural variation. The study intends to investigate and sample part of Prunus triloba wild populations, explore its variation pattern in fields, thus providing theoretical evidence for the conservation, selection and variety resource evolution of Prunus triloba and launch the introduction work of its wild resources, laying a foundation for cross breeding of Prunus triloba and related basic research. The results are listed as follows:1. The study investigated the distribution of wild Prunus triloba in Liaoning province, Hebei province and Beijing, took samples and made comparisons among representative populations. Prunus triloba is mainly distributed along both sides of valleys but rarely seen in mountain ridges. Large populations are concentrated in areas with gentle slope, among which there are Prunus davidiana and Prunus sibirica trees, and the majority is Prunus davidiana. More of the two species are distributed around Prunus triloba populations. Consequently, Prunus triloba has a complicated genetic background after long-term natural Election aid cross pollination.2. The study explored the phenotypic characteristics of6Prunus triloba wild populations. The results of variance analysis show that there are significant differences among populations and among individuals within populations. The variation among populations was slightly higher than that within populations, which indicated that the variance within populations was the main part of the phenotypic variation of Prunus triloba wild populations. Hence, the number of sampling from populations could be reduced while the number of sampling from individuals within populations could be increased in the genetic improvement of Prunus triloba, which means that it is essential to select superior individuals within populations.3. The results of UPGMA cluster analysis show that6Prunus triloba wild populations could be divided into2groups, but the cluster of characters were not based on the geographical distances, which reveal the discontinuous phenotypic variances within groups. The results of PAC indicate that the first6main factors could be used to replace parts of original characters with the accumulative contribution only up to57.33%. It is important to keep the integrity of populations in germplasm resource preservation of Prunus triloba.4. AFLP was employed to analyze genetic diversity of6wild populations of Prunus triloba. In this study,8pair primers previously identified were used to amplify specific DNA bands in the6Prunus triloba populations. As a result,256DNA bands were generated and206of them were polymorphic bands, which was80.47%of the total bands. Each primer pair generated129polymorphic bands on average and the mean polymorphism rate was50.26%. Among the6populations, the total observed number of alleles (Na) was1.8047and the mean was1.5026; the effective number of alleles (Ne) was1.2458and the average was1.2165; the Ne’s gene diversity index (H) was0.1567and the average H was0.1355; the total Shannon’s index (I) was0.2554and the average was0.2134. The results of genetic differentiation indicate that86.4%of the genetic variation should be among populations while13.53%should be within a population. The result of AFLP analysis reveals that dendrogram of6wild Prunus triloba populations is as similar as the clustering by geographic distance.5. Karyological data of P. triloba in Beijing population were investigated via squash method. The results showed all samples were octoploid (2n=8x=64). Asymmetry index was66.27%. The ratio of chromosome length, the longest chromosome to the shortest one was2.36. The karyotypes of all the test samples were made of m (7pairs), s (16paris) and st (9pairs) chromosomes. The karyotype was2B which belonged to a relative advanced type in evolutionary. Aneuploidy was observed in this study, the chromosome number ranged from61to64, the asymmetry index, centromere index and constitution of relative length etc. were different. The results confirmed that genetic diversity in cytological level were in accordance with the rich morphological variants among all the populations.The study can provide theoretical and data evidence for the conservation and exploitation of wild Prunus triloba germplasm resources and the introduction, domestication, propagation and cultivation of wid Prunus triloba. |
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