Molecular Evidence For Nature Hybridization And Maternal Origin Of Hybrids In Hippophae L.

Hybridization is the important mechanism in the evolution of angiosperms. It is thought that approximately 70% of angiosperms have experienced events of hybridization and polyploidization. Hybrid zones provide natural laboratories in which to study the evolutionary processes of hybridization. It provides an important chance to evaluate classification position of hybridization lineage and the mode of speciation. In the present study, we choose cpDNA trnS-G region as molecular marker to sequence the individuals of H. rhamnoides ssp. sinnesis, H. neurocarpa and H. goniocarpa in the two nature hybrid zones in Qilian Country, Qinghai, China. We aim to definite the paternal and maternal of H. goniocarpa and verification bidirectional hybridization through analysis genetic relationship from H. rhamnoides ssp. sinnesis, H. neurocarpa and H. goniocarpa. Meanwhile, the seqnences of the internal transcribed spaces (ITS) and cpDNA trnS-G region were sequenced and analyzed H. tibetana, H. neurocarpa and H. tibetana×H. neurocarpa in Dari Country, Qinghai, China. In order to verify hybrid generation of H. tibetana×H. neurocarpa from the putative parents and define the paternal and maternal origin. The study results as follow:TrnS-G region of 63 individuals in Gongbeiwan hybrid zone and 30 individuals in Babaohetan hybrid zone were sequenceed respectively. These were 657 bp lengths with 61 variation sites after alignment and 12 haplotypes in Gongbeiwan hybrid zone, and 658 bp lengths with 52 variation sites and 7 haplotypes in Babaohetan hybrid zone. H. goniocarpa shared common haplotypes from both H. rhamnoides ssp. sinnesis and H. neurocarpa in the two hybrid zones. It obviously supported hybrid origin of H. goniocarpa. Due to the maternal nature of cpDNA in Hippophae L., we had demonstrated that both H. rhamnoides ssp. sinensis and H. neurocarpa had acted as mothers in the hybridization events and the bidirectional hybridization occurred in the hybrid zones. Most individuals of H. goniocarpa were clustered to all of H. rhamnoides ssp. sinensis, and only few individuals of H. goniocarpa were clustered with H. neurocarpa. In addition, 4 typical haplotypes (H2, H3 , H4 and H7) were found in 6 individuals of H. goniocarpa, which were clustered with H. rhamnoides ssp. sinensis. These results indicated that the maternal plant of H. goniocarpa was mainly H. rhamnoides ssp. sinensis in the hybrid zones.ITS sequences of all individuals from the putative hybrid species H. tibetana×H. neurocarpa were found perfect additivity of putative parents H. tibetana and H. neurocarpa in the 229 site, which proved H. tibetana×H. neurocarpa had hybrid origin. The cpDNA trnS-G region sequences from H. neurocarpa, H. tibetana and putative hybrid indicated that H. tibetana×H. neurocarpa was different from H. neurocarpa based on 3 sites. According to plastid heredity law, the maternal plant of H. tibetana×H. neurocarpa was H. neurocarpa.