Ploidy and Karyotype Analysis of Different Populations of Paeonia mairei, an Endemic Species to China

抄録

Paeonia (Paeoniaceae) has an ancient origin, unique genetic evolution, and an isolated taxonomic status. China is the genetic origin of the genus Paeonia and an area rich in wild Paeonia resources. However, since herbaceous peony is not as well studied as woody peony, especially some species that are currently endemic to China. One such species that is endemic to China is Paeonia mairei, which is valuable germplasm for evolution research and cultivar improvement. Despite this, the karyotype of P. mairei remains inconclusive. In this study, root tips of plants from eight populations of P. mairei were used to examine their ploidy and to assess karyotype diversity. The results indicate that all eight P. mairei populations were tetraploid (2n=4x=20=12m+4sm+4st) with a 2A karyotype. Karyotype asymmetry ranged from 60.61% for P6 (Liangfengya, Foping County) to 63.12% for P4 (Ningqiang County). The chromosome length ratio ranged from 1.7398 (Dongchuan District) to 1.9660 (Dayi County) while the AI ranged from 4.4535 (Ningqiang County) to 5.6085 (Foping County). These findings indicate that the population in Foping County is relatively evolved whereas that in Ningqiang County is relatively primitive. Cluster analysis of karyotypic parameters showed that P3 (Dayi County) and P7 (Miaogou, Foping County) populations differed greatly from the other six populations, which could be clustered into two geographic branches. Our findings provide a scientific basis for exploring origin and evolutionary characteristics of P. mairei.