| Amygdalus ledebouriana Schlecht. (wild Almond) belong to Rosaceae, Prunoideae, Amygdalus, A. ledebouriana Schlecht. It is a very primitive tree species, precious, ancient and very scarce in the world today. Botanists call it "living fossil plants".On the basis of preliminary investigation of Germplasm Resources in A. ledebouriana Schlecht., growth and development of the situation, we carried out A study on propagate biological characteristics and genetic diversity of germplasm resources in A. ledebouriana Schlecht. and identification of genetic relationship of Amygdalus plants by SSR, including the different species and cultivation of different varieties, in order to grasp propagate biological characteristics, different groups genetic variation of A. ledebouriana Schlecht.. and genetic relationship of Amygdalus plants. This would provide a theoretical basis and genetics background information for hybrid breeding and breeding improved varieties, and lay the foundation for the genetic gene mapping of the cultivated species and their relative construction in Amygdalus. The main research results were as follows.1. Research results of flower bud differentiation in A. ledebouriana Schlecht.In this experiment, the paraffin section method is adapted to observe the developing process of flower bud differentiation of A. ledebouriana Schlecht. in TaCheng, Xingjiang. The results indicated that the floral morphodifferentiaion can be divided into five development stages: flower initial stage, sepal differentiation stage, petal differentiation stage, stamen differentiation stage and pistil differentiation stage. The floral morphological differentiation occurred at the mid ten-day period of June. There was intersectional phenomenon in each differentiation stage. From the starting of the flower bud differentiation to the pistil primordial differentiation, the whole process appeared intently between the last ten-day period of June and the first ten-day period of September. It took 90~100 days to finish morphodifferentiation.2. Research results of fertilization pollination biology in A. ledebouriana Schlecht.15 days after pollination on A. ledebouriana Schlecht., cross-pollination has higher average fruit setting rate than self-pollination and natural-pollination. 65.3% for the cross-pollination, 19.7% for self-pollination, 5.3% for natural-pollination. Overall fruit setting rate was the relatively low, It was 30%.3. Research results of seed multiplication in A. ledebouriana Schlecht.It is especially important for autumn sowing seed multiplication of depth of A. ledebouriana Schlecht.This is more appropriate for planting a depth of 4 ~ 5 cm, and has very high germination rate, Attention to the suppression of soil after sowing seeds, restore capillary effect of the soil, this would conducive to the absorption of water.4. Research results of tissue culture and plantlet regeneration in A. ledebouriana Schlecht.The seed of precious tertiary carry-over species in low region of Baerluk mountainous of Tacheng district in Xinjiang were used to establish the system in vitro plant and develop a feasible and practicable micropropagation system of A. ledebouriana Schlecht. Seed was plunged into gibberellin to breaking dormancy, after sanitizing Planting in primary medium. One month later, single bug was cultured in elongation medium.twenty day later, 100% in rooting percentage was obtained with 100mg.L-1IBA dip in 60 min, initial dark incubating for two weeks and continuous naturally lighting treatment in room. Improvement in rooting percentage was obtained . In vitro plant was transplanted in the same time to reduce humidity gradually, in this way the survival rate was higher.5. Research results of morphological diversity in A. ledebouriana Schlecht.In order to analyses morphological characteristics of the pattern of variation of natural populations of A. ledebouriana Schlecht., we determined the morphological variation of natural populations of A. ledebouriana Schlecht. in Xinjiang to found out the relationship between morphological variation and distribution.We compared fiften phenotypic traits based on 30 trees from five populations. The results showed that there was rich genetic variation among populations and within individuals. The variation within the populations is greater than that among populations. Based on the UPGMA cluster analysis, the five populations could be divided into three groups. There was no significant relationship between geographic distances and Euclidean distance. Principal component analysis showed that Length of leaf /Maximal width of leaf index, Width of seed, Length of seed/width of seed index, Length of leaf, Maximal width of leaf, The weight of per 1000 seeds were the most important phenotypic traits which lead to the morphological variation of A. ledebouriana Schlecht.6. Research results of SSR genetic diversity in A. ledebouriana Schlecht.The genetic diversity and genetic structure as well as genetic differentiation of natural populations of A. ledebouriana Schlecht. were investigated with ten pair SSR primers for a total of 150 individuals from five populations sampled. The purpose of the study was to determine the genetic structure and diversity in these eco-geographical populations. The results indicated that: an average of 9.2 bands was detected in the five populations. The percentage of polymorphic bands in Yumin population (92.77%) was the highest in the five populations. The average Nei's gene diversity index was 0.262 for all the loci. Totally, 92 polymorphic loci were detected and the percentage of polymorphic loci (P) was 100%,88.04%,85.87%,85.87%,90.21%,92.39%, respectively, at the species level and Burjin, Habahe, Tacheng, Tuoli and Yumin population levels. The Nei's gene diversity index (H = 0.2971) and Shannon's information index (I=0.4421) in the species level were higher than in the population level. The Nei's gene diversity index and Shannon's information index in the five populations were Yumin > Tuoli >Habahe > Tacheng>Burjin. The results of AMOVA had been indicated that the variance components of within populations and among populations contributing to total genetic variance were 63.56% and 36.44%, The results showed that there was rich genetic variation within individuals. The UPGMA cluster analysis indicated the five populations could be divided into three groups. There was no significant relationship between geographic distances and Euclidean distance.Tacheng population and Habahe population were the highest in genetic identity and the closest in genetic distance. Yumin population and Tuoli population were the close relations. Burjin population were relatively independent populations. Concurrently, Gene flow between the populations was 0.9197 based on genetic differentiation coefficient (GST= 0.0598). indicating that genetic recombination between populations is quite small , which probably is related to environmental adaptations of A. Ledebouriana Schlecht. and population isolation in their high mountain habitat. on the basis of the study of population genetic structure and the highest genetic diversity, Yumin population should be given a high priority consideration in A. ledebouriana Schlecht. population's in situ germplasm conservation.7. A preliminary study on comparison and coupling of morphological and DNA markers in A. ledebouriana Schlecht.The diversity levels are different among morphological and DNA markers. Phenotypic characteristics had greater variability than the DNA molecular markers. The former was more sensitive to environment. Genetic cluster analysis is similar based on the results of morphological and DNA markers, the five populations could be divided into three groups. But there are different groups sort of individual locations, reflecting the similarities and difference about the analysis of the relationship between population with the two kinds of markers, It could be concluded that there was coupling and relevance to some extent in evaluating genetic diversity with the same experiment sampling by morphological and SSR marker variation. However, there was also differences. In research, the two can complement each other.8. Identification of Genetic Relationship of Amygdalus plants by SSRThe genetic relationship among 55 Amygdalus plants collections, belonging to 6 species and collected from both homeland and abroad were identified via SSR molecular marker technique. 12 pairs of primers were selected out to amplify 75 polymorphism bands. The genetic distance between these collections were analyzed with cluster analysis based on these bands. The result showed that the genetic distance between them were different. And most of the cultivars were classified in the same group when the genetic similarity coefficient was less than 0.68. The cultivars from the same area were clustered in the same group. Compared the relationship among A. communis L., A.ledebouriana Schlecht. and A.pedunculata Pall., A.mongolica Moxim., A.tangutica Batal. and A.triloba (Lindl) Ricker., the relationship between A. communis L. and A.ledebouriana Schlecht. is closer than the relationship between A. communis L. and A.pedunculata Pall., A.mongolica Moxim., A.tangutica Batal. and A.triloba (Lindl) Ricker. This results gave a clearly outlook of the genetic relationship and genetic diversity level among Amygdalus plants germplasm.
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