Interspecies Introgression Hybridization In Liriodendron Revealed By SSR Markers

This paper first reported the interspecies introgression hybridzation in Liriodendron. Based on parentage analysis of open-pollination progenies from 6 experimental populations that were constituted of Liriodendron chinense, L. tulipifera and hybrid Liriodendron, both the mating patterns and the extent of introgression hybridization were explored using SSR markers. The results were as follows:One pair of species-specific primers in Liriodendron were screened from 176 pair SSR primers, by which the amplification fragment sizes were 190 bp in L. chinense, 180 bp in L. tulipifera, and both 190 bp and 180 bp in hybrid Liriodendron respectively.The introgression hybridization was detected in 6 experimental populations of mixed tulip species based on parantage analysis of open-pollination progenies. It was certain that introgressin hybridization happened in all 6 experimental populations of Liriodendron, although the orientation and extent of gene introgressin were different among populations. For each species of Liriodendron, its extent of introgression hybridization was close related to the number of adults in the mixed forest.To detect the extent of introgression hybridization in Liriodendron quantitatively, the regression coefficient of gene frequency between progenies and their parents was taken as hybrid index. The hybrid indexes in 5 populations of Nanjing, Zhejiang Anji A,B,C and Zhenjiang Xiashu B were 0.2549,0.9547,0.9805,0.9547, and 0.5658 respectively. The extent of introgression of L. tulipifera was stronger than that of L. chinense in Nanjing population, while in other populations, the other way round.The genetic diversity were compared between parent population and their offspring. It seemed that the genetic diversity of progeny population were lower than that of parent population, indicating the risk of genetic diversity decrease. The strategies of conservation of Liriodendron were also discussed in this paper.