Evaluation Technical Code And Genetic Diversity Research On Chinese Jujube Germplasm Resources

Chinese jujube originated from China with a broad distribution and rather abundant resources. It is native to China as an important economic fruits forest. Characterization, evaluation and genetic diversity were main and basic contents for germplasm resources research, innovationand and utilization. To standardize characterization and evaluation and to reveal the genetic diversity of Chinese jujubes,300 accession germplasm resources preserved in China National Jujube Field Genebank were investigated and studied systematically by phenotypic and molecular marker data collection, processing and statistical analysis. Based on related documentation and our research, Charaterization and evaluation system for jujube had been established and standardized further. Genetic diversity of Chinese jujube were studied by morphological and agricultural characters and molecular marker data. Combining these data, the core collection of Chinese jujube was constructed. Main results for this research were as follows.1. Establishment of characterization system for jujube germplasm resources:In the study, based on previous research results, characterization system for jujube germplasm resources was proposed.66 characterization characters were determined by improvement, deletion and supplement following principles of significant differences among individuals, mature characterization techniques and having significant for classification and identification, genetic diversity research, breeding and production utilization. It was further standardized that observation places and objects selection, field management measures and data collection and processing demands. Each character was interpreted about its period of data collection, sampling, observing and data processing methods. In addition, some characters were classified by morphological diagrammatic drawings.2. Standardization of evaluation for elite and rare jujube germplasm resources:22 important characters were selected based on demands of scientific research and production.Evaluation characters for elite jujube included 11 ones of yield per unit area, percentage of fruits to fruiting shoots, fruit uniformity, fruit texture, SSC in fresh fruit, edible ratio of fresh fruit, storage habit of fresh frui, dried ratio of fruit, sugar content of dried fruit, resistance to fruit cracking and brown cortex. Elite table jujube criterions were that its characters of yield per unit area, fruit texture and SSC in fresh fruit must reach their evaluation indexes at the same time including having the other one reaching its evaluation index at least. Elite drying jujube criterions were that its characters of yield per unit area, dried ratio of fruit and sugar content of dried fruit must reach their evaluation indexes at the same time including having the other one reaching its evaluation index at least.Evaluation characters for rare jujube included 16 ones of secondary shoot tortuosity, pollen existence, yield per unit area, days of fruit developmental phase, fruit weight, Fruit color, fruit shape, sepal persistence, pit state, percentage of fruits having seeds, SSC in fresh fruit, TAC in fresh fruit, Vc in fresh fruit, dried ratio of fruit, resistance to fruit cracking and brown cortex. Rare jujube criterions were any one character reach its evaluation index at least.3. Genetic diversity of jujube germplasm resources based on phenotypic qualitative characters:37 quality were divided into 130 classifications. For 200 accessions of jujube germplasm resources, the frequency of occurrence of those classifications were from 1 to 198 with effective percentages of from 0.5% to 99.0%. Shannon-Wiener diversity index of qualitative characters was 0.97, which showed rich genetic diversity and goog evenness.4. Genetic diversity of jujube germplasm resources based on phenotypic quantitative characters:(1) For 200 accessions of jujube germplasm resources, coefficients of variation of 23 quantitive characters were from 2.39%～86.84% and their average diversity index of Shannon-Wiener was 1.92, which showed more diversity than that of qualitative characters. (2) 10 charaters’ asympotic significances were over 0.05 by Kolmogorov-Smirnov test which included Extension shoot internode length, Extension shoot thick, Secondary shoot length, Fruiting shoot length, Fruit development period, Fruit vertical diameter, Fruit transverse diameter, SSC in fresh fruit, Soluble sugar content in fresh fruit and Vc in fresh fruit, which showed their data were normal distribution. The other 13 characters of Extension shoot length, Leaf number per fruiting shoot, Flower number per inflorescence, Flower diameter, Fruiting age, Percentage of fruits to fruiting shoot, Fruit weight, Leaf length, Leaf width, Fresh pit weight, Seed ratio, TAC in fresh frui and Edible ratio of fresh fruit were abnormal distribution. (3) The result of correlation analysis among quantitative characters showed that there were 68 pairs having extremely significant correlation, of which 46 ones were positive correlation and 22 ones were negative correlation; there were 27 pairs having significant correlation, of which 14 ones were positive correlation and 13 ones were negative correlation. For example, There were extremely significant positive correlations between Extension shoot length and its internode length or thickness, Secondary shoot length, Fruiting shoot length or Leaf number per fruiting shoot; there were extremely significant positive correlations between Leaf number per fruiting shoot and Leaf length or width. (4) All of quantitative characters were divided into five groups by R-type variable clustering:Group 1 included 4 characters which all were fruit traits; group 2 included 3 characters which all were branch traits; Group 3 included 5 characters which were fruit or branch traits; Group 4 included 2 characters which all were fruit traits; Group 5 included 9 characters which were branch, leaf, flower, fruit or yield traits. (5) Degree of being suitable to principal component analysis of 23 quantitive characters was normal. The results of principal component analysis showed that 10 principal components were determined whose rates of contribution were 16.509%,26.141%,34.168%,41.512%,48.593%,54.866%,60.392%, 65.238% and 69.989% respectively and cumulative rates of contribution was 74.343%, i.e. more than 74% genetic diversity information could be retained. (6) The result of comprehensive analysis above showed that 12 characters of Extension shoot length, Extension shoot internode length, Extension shoot thickness, Fruiting shoot length, Leaf number per fruiting shoot, Fruiting age, Fruit weight, Fruit vertical diameter, Fruit transverse diameter, Fresh pit weight, Vc in fresh fruit and Edible ratio of fresh fruit had most diversity and shoud be considered as important characterization and evaluation items primarily. The secondary characters were Secondary shoot length, Leaf length, Leaf width, Flower number per inflorescence, SSC and Soluble sugar content in fresh fruit. The last were Flower diameter, Percentage of fruits to fruiting shoot, Fruit development period, Seed ratio and TAC in fresh fruit.5. Genetic diversity of jujube germplasm resources based on molecular marker data:All of 200 samples were identified by AFLP melecular marker technique using 10 pairs of primers selected from 64 ones.1398 loci were detected. The number of polymorphic loci was 1287. The percentage of polymorphic loci was 83.10%. The observed number of alleles was 1.8855. The effective number of alleles was 1.5059. Nei’s gene diversity was 0.2977 and Shannon’s Information index was 0.4429.6. Hierarchical clustering and genetic relationship analysis:Combining phenotypic and molecular marker data,200 accessions were hierarchically clustered by Euclidean genetic distance and UPGMA method. Their genetic distances were from 1.80 to 8.08. It was suitable to divide them into 8 groups and 10 subgroups according to practical situation. Genetic relationship among those samples and groups had been analyzed and it was proposed for the first time that the reason of region Crossing among different group should be related closely to rivers’ changes in the long history.7. Core collection Construction of jujube germplasm resources:46 accessions of core collection were selected by combining phenotypic and molecular marker data of 200 accessions of initial collection. For 46 accessions of core collecton, the retention rates of quality characters and genetic information were 100% and 95.88% respectively; the range accordance rate, mean difference rate and genetic information retention rate of quantitive characters were 92.70%,1.95% and 95.83% respectively; for molecular marker, the retention rates of number of polymorphic loci and percentage of polymorphic loci were 92.44% and 95.18% respectively; the retention rates of observed number of alleles, effective number of alleles, Nei’s gene diversity and Shannon’s information index were 97.11%,99.86%,100.25% and 100.96% respectively. So core collection was representative to its initial collection with a appropriate proportion.