Study on Chromosomal Structural Heterozygosity in Paeonia Emodi, an Endangered Species

Chromosomal meiotic behavior in pollen mother cells (PMCs) of Paeonia emodi, an endangered species, was investigated in natural population represented by nine individuals. The results showed that: (1) Mean chromosome configuration was 2n = 10 = 0.20 I + 4.90 II at metaphase. Most of the chromosomes were ring bivalents, but some were rod bivalents or univalents. The existence of rod bivalent and univalent indicated the differentiation between the homologous chromosomes, most probably due to chromosomal structural heterozygosity. (2) All individuals studied were chromosomal structural heterozygotes, i.e., inversion, as indicated by bridge and/or fragment. (3) There were some variations among individuals in size of fragments, which indicated that different inversions existed in this species, i.e., paracentric inversion polymorphisms. Chromosomal structural heterozygosity is a common phenomenon in Paeonia. Further research is necessary to probe into the reasons that structural heterozygosity exists widely, and whether there is relationship between heterozygosity and ecological adaptation in this species.