| Genetic diversity of Wild pear resources is the base of pear breeding material. In order to know the genetic diversity, wild pear population is taking as research object. Genetic diversity among wild pear resources were studied, using some morphological traits and SSR markers. The suitable population size for Duli regeneration was determined. According to analysis of the correlation between morphological traits and genetic diversity of wild pear with geographical location,indentificaiton of the spatial genetic structure of Jingmen Tangli. SSR markers were used to identify and study the genetic diversity of hybrid progenies from’Shanli’×’Duli’. providing scientific and theoretical basis for making a criteria for regenerating,conserving and collecting wild pear resources.The main results as follows:1. Seven groups with5,8,10,15,20,30and40seedlings, respectively, were selected randomly from a wild pear population of59individuals. Polymorphic site120～253, percentage of polymorphic site47.00%～89.83%, Nei’s genetic diversity index0.13-0.15, Shannon’s information index0.21～0.26, number of average alleles1.47～1.99and number of effective alleles1.19～1.20of each group were analyzed with29SSR markers. There is no significant difference in genetic diversity index between control group and selected group which has more than15seedlings. The suitable population sizes for wild pear conservation should be above15individuals. Numbers and changes (increase or decrease) of rare alleles in each group were analyzed also,it revealed that population sizes effected the number of rare alleles significantly, and the numbers decreased with less individuals.2. Genetic diversity among Jingmen Tangli was studied, using some morphological traits and SSR markers. The average coefficient of Shannon-weave index were0.29(ranged between0.11and0.75), based on investigation of morphological traits. Using26SSR primers,290discernible DNA fragments were generated, among which262(90.34%) were polymorphic. The mean of polymorphism information content (PIC) for the SSR primers was0.81. The mean of Expected heterozygosity (He), Observed heterozygosity (Ho) and Number of effective alleles(Ne) were0.13,0.24and1.18respectively, among all tested individuals the results showed that genetic diversity was lower among the nature population. The index of genetic diversity may provide the reference of genetic resource protection and exploitation strategies of wild resources. According to analysis of the correlation between morphological traits and genetic diversity among nature population with geographical location, indicate that genetic diversity level is more influenced by the location of samples. The relationship between morphological and SSR-based distance was significant positively correlated (r=0.61,P=0.01) by Mantel testing. Based on morphological traicts,SSR data and spatial autocorrelation coefficient, the result of the dendrogram of Jingmen Pyrus betulaefolia Bunge indicate that a few individual plants were high specificity and showed significantly positive spatial genetic structures at distance less than45m.3. SSR markers were used to identify and study the genetic diversity and hybridism, of hybrid progenies from crosses of Duli as female. The hybrid nature of51offsprings from the two cross combinations of Duli and Shanli was analyzed. The analysis of SSR genetic diversity showed that the Number of effective alleles, Nei’s genetic diversity index, Shannon genetic diversity was1.19,0.14and0.26respectively.48hybrids was identified from51F1seedlings of’Shanli’×’Duli’ pear by19pairs SSR primers, the identification rate was94.11%.51progenies had19markers present only in father and29markers present in both parents in primer KU10,and the identification rate was92.45%. Some markers were absent in28and3F1seedlings in primer NB103a and NH021a respectively. The cluster analysis of SSR data indicated that the genetic variation of hybrids from the two cross combinations was obviously, and the genetic diversity between the two combinations of crosses was obviously different.The identification of hybrids and genetic diversity of pear can be assessed efficiently by SSR markers, and the cross breeding is an effective way to obtain variant strains. |
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