| Taking the endangered plant species Sinocalycanthus chinensis as the research object, the effect of habitat fragmentation on S. chinensis's reproductive organs and genetic diversity was studied. In addition, artificial hybridization were conducted between wild populations and within population and the morphological variation of fruits and seeds were determined in order to find the optimal outcrossing distance of S.chinensis based on mating success and the characters of the offspring. These results could provide theoretical basis for multiply and rejuvenation of S. chinensis. The results showed as the followings:1. The reproductive organs variation of three S. chinensis populations in the main distribution areas (DMS,DLS and LXS) were analyzed. The results showed that the morphological variation of reproductive organs were ubiquity within and among populations. The variation degree of different reproductive organs was different, and so did the character indexes of the same reproductive organs, which might be due to the genetic factors and the environmental factors. A certain degree of the morphological differentiation were observed among populations. For instance, S. chinensis in DLS population had more petal size numbers and larger Outer-petal size, while S. chinensis in DMS population had more stamen and pistil, but LXS population was longer than others on pistil length. The weight and the size of fruits of S. chinensis in DMS population were the first, and followed by those in DLS population and LXS population. Most indexes had significant differences among populations, but the fruit morphology of S. chinensis in DLS population were wide-short in sharp, significantly differing from the others. The size and weight of S. chinensis seeds in DLS population were the biggest and weightiest, and those in DMS and LXS population were relatively small and light. There were significant differences between them. S. chinensis seeds in LXS population was long-narrow in sharp with significant differences from the other populations. This indicated that the variation of the reproductive organs among S.chinensis populations might be due to the heterogeneity of micro-habitat, population isolation and genetic drift.2. S. chinensis in DMS population was used as the female parent, artificial pollination was conducted using pollens collected from S. chinensis populations in three main distribution areas, pollens collected from different S. chinensis populations in Linan City and different distances of pollens collected from DMS population. The setting rate of fruit and seed and the morphological variation of the offsprings were analyzed. The results showed that the setting rate of fruit and seed and the seeds number per fruit were different in different treatment. In the different main distribution areas treatments, cross-compatibility of LXS varieties pollen was the worst, and both of the cross-compatibility of the farther (DLS) and nearer (DMS) varieties pollen relatively good. In artificial hybridization between different populations of pollen in linan, cross-compatibility of QLF varieties pollen was the worst, seed size per fruit of TSJ varieties pollen was also poor. In artificial hybridization between different distances of pollen in DMS population, fruit setting rate and seed setting rate were worst at 30-50m of the outcrossing distance, while seed size per fruit was the worst at 80-100m of the outcrossing distance. This indicated that the cross-compatibility might be influenced by the cross-compatibility of genotype and the environmental factors.The morphological variation of reproductive organs were ubiquity both within and among different artificial hybridization treatments. Kruskal-Wallis Test showed that at the same scale of artificial hybridization, all of the characters of seeds except the seed length/seed width were different in different treatment with significant difference, indicating that the influence of the origin of pollen on the characteristics of seeds was great. The characters of fruits were different in the arfificial hybridization of different distance pollen, but only few characters were extremely significant different. However, there were extremely significant differences in all of the characters of fruits in the treatments of different main distribution areas and different populations in Linan. This indicated that the differences of the varieties pollen aslo have great influence on the fruits after artificial hybridization.In the different main distribution areas treatments, the fruits in treatment hybridizated with DMS pollen was the largest, while that with LXS pollen was the smallest. The weight and the size of seeds in the treatment hybridizated with DLS pollen were significant higher than the other treatments. In artificial hybridization between different populations of pollen in linan, bothe the characteristics of fruits and seeds in the treatment hybridizated with SXW pollen were the best, followed by DMS pollen. Whereas those in treatment hybridizated with QLF pollen and TSJ pollen were relatively small with significantly differences in fruit length, fruit weight, seed size per fruit, fruit-shell weight, seed weight and seed length. In artificial hybridization between different distances of pollen in DMS population, there were no significantly differences in the fruit characteristics in different treatments. The characteristics of seeds mainly differed between YJⅡ(apart from 30～50m) and other treatments. all of the characters of seeds in treatment hybridizated with YJⅡpollen were the smallest with significant differences in seed weight, seed length and seed thick. 3. Using inter-simple sequence repeat (ISSR) makers, genetic diversity and genetic differentiation of S.chinensis populations, which collected from the main distribution areas(DMS,DLS and LXS) were analyzed. The results showed that the genetic diversity of S. chinensis at species level was high, while that at population level was low. The percentage of polymorphic loci (P). Shannon's imformation index (I) and Nei's gene diversity (h) of DMS S. chinensis population was the highest, followed by LXS population and DLS population. The analysis of molecular variance (AMOVA) demonstrated that genetic variation existed both within population and among populations. Genetic differentiation among populations were significant (Gst=0.6050). The gene flow among populations was as low as 0.3264 which might be the main factor of the genetic differentiation among populations. The clustered result for 5 S. chinensis populations by unweighted pair group method arithmetic average (UPGMA) suggested DMS population and LXS population with the nearest distance were clustered into one group, while DLS population was clustered into other group. The genetic differentiation might be due to the gene communication disorder induced by population isolation.4. Correlation analysis between reproductive organs variation and genetic diversity indicated that there was no significant correlation either between flower and genetic diversity or between fruit and genetic diversity, indicating that the other factors but not genetic factors might be the main cause lead to morphological variation of fruits and flowers within population. However, morphological variation of seeds was positively correlated with genetic diversity, among them, it was significantly correlated with Shannon's imformation index (I) and Nei's gene diversity (h), which suggested that genetic diversity was the main factor which caused the morphological variation of seeds within population. Moreover, correlation analysis between reproductive organs differentiation and genetic differentiation among populations indicated that morphological differentiation of flowers was significantly positively correlated with genetic differentiation, whereas there was no significant correlation either between morphological differentiation of fruits and genetic differentiation or between morphological differentiation of seeds and genetic differentiation. |
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