Abstract:

【Objective】 Assessing the genetic diversity between wild and cultivated accessions of eight taxonomic groups in two species, five subspecies under Pisum genus, and analyzing the population structure and their genetic relationships among various groups of taxonomy, the study try to verify the fitness of traditionally botanical taxonomic system under Pisum genus and to provide essential information for the exploration and utilization of wild relatives of pea genetic resources. 【Method】 One hundred and ninety-seven Pisum accessions from 62 counties of five continents were employed for SSR analysis using 21 polymorphic primer pairs in this study. Except for cultivated field pea Pisum sativum subsp. sativum var. sativum (94 genotypes), also included were wild relative genotypes that were classified as P. fulvum, P. sativum subsp. abyssinicum, P. sativum subsp. asiaticum, P. sativum subsp. transcaucasicum, P. sativum subsp. elatius var. elatius, P. sativum subsp. elatius var. pumilio and P. sativum subsp. sativum var. arvense (103 genotypes). The PCA analyses and three-dimensional PCA graphs were conducted and drawn by NTSYSpc 2.2d statistical package. Nei78 genetic distances among groups of genetic resources were calculated, and cluster analysis using UPGMA method was carried out by using Popgene V1.32 statistical package, the dendrogram were drawn by MEGA3.1 statistical package. Allelic statistics were carried out by Popgene V1.32. The significance test between groups of genotypes was carried out by Fstat V2.9.3.2 statistical package.【Result】One hundred and four polymorphic bands were amplified using 21 SSR primer pairs with unambiguous unique polymorphic bands. 4.95 alleles were detected by each SSR primer pair in average, of which 65.56% were effective alleles for diversity. PSAD270, PSAC58, PSAA18, PSAC75, PSAA175 and PSAB72 were the most effective SSR pairs. SSR alleles were uniformly distributed among botanical taxon units under pisum genus, but significant difference appeared in most pairwise comparisons for genetic diversity between taxon unit based groups of genetic resources. Genetic diversity level of wild species P. fulvum was much lower than the cultivated species P. sativum. Under species P. sativum, P. sativum ssp. sativum var. sativum and P. sativum ssp. asiaticum were the highest in gentic diversity, followed by P. sativum ssp. elatius var. elatius and P. sativum ssp. transcaucasicum, P. sativum ssp. elatius var. pumilio, P. sativum ssp. sativum var. arvense and P. sativum ssp. abyssinicum were the lowest. Four gene pool clusters were detected under Pisum genus by using PCA analysis. Gene pool “fulvum” mainly consisted of wild species Pisum fulvum, gene pool “abyssinicum” mainly consisted of P. sativum ssp. abyssinicum, and gene pool “arvense” mainly consisted of P. sativum ssp. sativum var. arvense. While gene pool “sativum” were composed by five botanical taxon units, they are P. sativum ssp. asiaticum, P. sativum ssp. elatius var. elatius, P. sativum ssp. transcaucasicum, P. sativum ssp. elatius var. pumilio and P. sativum ssp. sativum var. sativum. “sativum” gene pool constructed the primary gene pool of cultivated genetic resources;“fulvum” gene pool, “abyssinicum” gene pool and “arvense” gene pool together constructed the secondary gene pool of cultivated genetic resources. Pairwise Nei78 genetic distance among botanical taxon based groups of pea genetic resources ranged from 7.531 to 35.956, three large cluster groups were identified based on the UPGMA dendrogram. Group I equals to “sativum” and “arvense” gene pools, Group II equals to “abyssinicum” gene pool, and Group III equals to “fulvum” gene pool. The UPGMA clustering results generally support the PCA clustering results.【Conclusion】 There were significant differences among most botanical groups under Pisum genus, with clear separation of four gene pools for genetic diversity structure. The research results partially support the traditional botanical taxonomy under Pisum genus, and point out its advantage and shortcoming. In order to broaden the genetic bases of pea varieties, the genetic potentials in the four gene pools should be thoroughly exploited.

Key words: Pisum genus, SSR, genetic diversity, botanical taxonomy, gene pool