Abstract:

【Objective】 Assessing the genetic diversity between Chinese and alien accessions of cultivated pea (Pisum sativum L.) sampled from National Gene Bank, analyzing their differentiation on allelic loci and population structure, the study try to evaluate the importance and value of these conserved genetic resources, to provide essential information for guidance on strategy and direction choices for future studies of pea genetic resources in China, and for the effective exploration and utilization of global pea genetic resources. 【Method】 1 984 cultivated pea accessions from 66 countries of five continents and 28 provinces of China were employed for SSR analysis using 21 polymorphic primer pairs to detect genetic diversity and population structure. The Structure 2.2 software was used for population structure detection, definition of real population number, genotype allocation to its real population, and calculation of related parameters. Calculation of genetic distance, PCA analyses, 3-dimensional PCA graph, was conducted and drawn by NTSYSpc 2.2d statistical package. Allelic statistics were carried out by Popgene V1.32. The significance test between groups of genotypes was carried out by Fstat 2.9.3.2 statistical package. 【Result】 Based on SSR markers, the observed number of alleles (NA), the effective number of alleles (NE), the ratio of NE/NA, the allelic richness (AR), the gene diversity (GD) and the Shannon's information index (I) of pea germplasm resources from China and foreign countries were thoroughly compared. Except the observed number of alleles (NA), the values of other parameters on genetic diversity detected from Chinese landraces were all higher than that from foreign germplasm resources. Among the 21 tested SSR loci, the difference between Chinese and foreign germplasm collections appeared in 7 SSR loci. The population structure analysis divided all the 1 984 tested genotypes into 3 populations (Pop A, Pop B and Pop C). Pop A consisted of almost all alien accessions (96.49% genotypes of all alien accessions), referred to foreign germplasm population. Pop B consisted of most accessions from Shaanxi and Inner Mongolia (88.18% genotypes of this population), standing for typical Chinese spring sowing germplasm population. Pop C consisted of majority (52.05% genotypes of this population) from Chinese winter sowing areas, and minority (47.44% genotypes of this population) from Chinese spring sowing areas, standing for Chinese winter sowing and spring sowing (except Inner Mongolia and Shaanxi) germplasm population. There were significant differences among the three populations. 3-dimension PCA graph showed 3 concentrated domains with clear boundaries in between, each of the domain (gene pools I, II and II) approximated to Pop A, Pop B and Pop C. 【Conclusion】 The genetic diversity level of domestic Chinese accessions as a group was generally higher than that of alien group, while the level of difference among genotypes within alien group on each parameter was higher than that within Chinese accession group. Three independent populations named Pop A, Pop B and Pop C were detected by population structure analysis, with significant difference in genetic diversity among them. 3-dimension PCA graph showed 3 concentrated domains (gene pools I, II and II) with obvious boundaries in between. Gene pool I concentrated alien genotypes, Gene pool II concentrated Shaanxi and Inner Mongolian genotypes, and Gene pool III concentrated genotypes from Chinese winter sowing areas and spring sowing areas except Shaanxi and Inner Mongolia. By pairs, the three gene pools detected by PCA almost equal to the three populations identified by Structure 2.2 in genotype composition. Pop A approximated to Gene pool I, Pop B approximated to Gene pool II,and Pop C approximated to Gene pool III. Results from PCA fully supported the findings from population structure analysis, within global cultivated pea genetic resources the three gene pools can be defined. Alien genotypes constructed Gene pool I, Chinese genotypes constructed Gene pool II and Gene pool III, which revealed the importance of Chinese and alien collections and Chinese collection was superior.

Key words: pea (Pisum sativum L.), germplasm resources, SSR, genetic diversity, population structure, gene pool