Abstract: China is the second producer of pea in the world with a collection of 5 000 accessions, around 20% of which were introduced from 70 foreign countries. It is essential to assess the genetic diversity among alien pea (Pisum sativum L.) germplasm accessions, to analyze their genetic relationships among various groups of gene pool from different geographical/ecological areas, and to constitute core collection of alien genetic resources of pea. The information generated from the study will be very helpful for the exploration and utilization of overseas pea genetic resources. For the purpose above, 21 SSR primer pairs with unambiguous unique polymorphic bands and their optimum annealing temperatures were successfully screened out from the 111 candidates. Pea’s SSR marker experimental system was optimized thereafter, and adopted for genetic diversity analysis and for constitution of a core collection among the 731 pea accessions from 67 countries of various continents. Using 21 SSR primer pairs, 109 poly-morphic bands were amplified, and 5.19 alleles were detected by each SSR primer pairs on an average. SSR alleles were not uni-formly distributed among continents, and the number of effective alleles and Shannon’s information index (I) were much varied among continental based groups of genetic resources. Significant difference appeared in the pairwise comparisons for genetic diversity between continental based groups of genetic resources. Asia group had the highest level of genetic diversity (I = 1.1753), followed by Europe (I = 1.1387), USSR (I = 1.0285), America (I = 1.0196), Africa (I = 0.9254), and Oceania (I = 0.8608) groups. Two large cluster groups and four cluster sub-groups were identified based on the dendrogram of pairwise Nei78 genetic distance. The clustering results of alien genetic resources revealed geographically broad correlation to their genetic diversity. Three types of population structure within 731 alien pea accessions were inferred by Structure analysis, which also broadly correlated to their geographic origins. A scientific and logical standard methodology for construction of core collection based on Structure analysis was designed and applied in this study, a subset (6.57% of the whole collection) of 48 accessions representing 84.4% of the whole allelic variability was proposed to be a core collection.

Key words: Pisum sativum L., SSR, Genetic diversity, Core collection, Alien genetic resources