用RAPD检测华山新麦草自然居群的遗传结构和居群分化

Genetic structure and differentiation of Psathyrostachys huashanica populations detected with RAPD markers

华山新麦草特产于我国陕西华山,为国家一级重点保护植物。应用RAPD技术,用2 0条随机引物对黄埔峪、仙峪、华山峪3个居群不同海拔的13个亚居群共2 6 6个华山新麦草取样个体进行扩增,共得12 2个扩增片段。平均每个引物得到的扩增片段数为6 .1(2～10 )。实验数据的统计分析表明:黄埔峪居群的多态性位点比率为6 0 .6 6 % ,仙峪居群的多态性位点比率为90 .98% ,华山峪居群的多态性位点比率为95 .0 8% ,总的多态性位点比率为95 .0 8% ,说明华山新麦草具有较高的遗传变异性。Shannon多样性指数(0 .330 6 )和基因分化系数(GST=0 .32 6 3)揭示了华山新麦草居群遗传变异多存在于亚居群内。华山新麦草亚居群间的基因流N m=1.0 32 2 ,低于一般风媒传粉植物(N m=5 .2 4 )的基因流水平。亚居群间平均的遗传距离为0 .15 71(变化范围:0 .0 0 2 2～0 .2 90 1) ,最大的遗传距离值出现在黄埔峪亚居群(hp1)和华山峪高海拔亚居群(h8)之间,仙峪亚居群与华山峪高海拔亚居群之间以及华山峪高海拔亚居群与低海拔亚居群之间的遗传距离值也较大。遗传距离与海拔垂直距离之间的相关性分析表明二者有显著的相关性(p<0 .0 1)。聚类分析和主成分分析也显示华山新麦草自然居群已发生明显分化,主要表现为黄埔峪居群。

Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys in Triticeae. Psathyrostachys distributes in center of middle Asia and Caucasus Mt., while P. huashanica, a species endemic to China, is only located in Mountain Hua in Shaanxi Province. At present, the populations of this species are decreasing, and reaching the edge of extinction. Due to the distributing limitation and importance as breeding material for germplasm storage, it has been considered as the first class of national protected rare plants. For this reason, the present study is significant in probing plant flora, origin and evolution of Triticeae and crop breeding. Randomly amplified polymorphic DNA (RAPD) markers were used to analyze genetic structure and differentiation of P. huashanica populations sampled in three valleys (Huangpu, Xian and Huashan Valleys) in Mt.Hua. One hundred and twenty-two RAPD fragments were obtained in all 266 individuals with 20 primers with mean of 6.1 (2～10) fragments per primer. The percentage of polymorphic loci (PPB) is 60.66% in Huangpu Valley, 90.98% in Xian Valley, 95.08% in Huashan Valley, and the total PPB is 95.08%, which indicated a highly genetic variability of P. huashanica. The Shannon's Information index and G_(ST) are 0.3306 and 0.3263, respectively, indicating that there were more genetic variations within the subpopulations than those among the subpopulations. The gene flow among the subpopulations of P. huashanica (Nm=1.0322) is much less than that of the common anemophytes (Nm=5.24). Mean genetic distance is 0.1571(range:0.0022～0.2901). The highest value of genetic distance was found between the subpopulations (hp1) of Huangpu Valley and the highest altitude subpopulation (h8) of Huashan Valley. Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude. Clustering analysis and principal coordinate analysis revealed the genetic differentiation among the populations of P. huashanica. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.