湖北野生春兰资源遗传多样性的ISSR分析

Genetic diversity of wild Cymbidium goeringii (Orchidaceae) populations from Hubei based on ISSR analysis

近年来,由于过度采挖和生境片断化,湖北野生春兰(Cymbidiumgoeringii)资源正面临着灭绝的危险。本文采用ISSR分子标记技术对湖北省内的11个春兰野生居群共325个个体的遗传多样性水平及居群遗传结构进行了研究。11个引物共检测到127个位点,其中112个为多态位点,占88.19%。POPGENE分析结果表明:与其他兰科植物相比,春兰具有丰富的遗传变异(在物种水平上,He=0.2628,Ho=0.4037;在居群水平上,PPL=63.06%,He=0.1945,Ho=0.2958)。Nei's遗传多样性分析和AMOVA分析表明,各居群间产生了一定程度的遗传分化(GST=0.2440,FST=0.2207)。居群间一定程度的遗传分化可能是由生境破坏和基因流障碍(Nm=0.8828)引起。UPGMA聚类分析可知,与其他居群相比,恩施地区的5个居群,即巴东(BD)、福宝山(FBS)、宣恩(XE)、毛坝(MB)、来凤(LF)优先聚成一支,而大悟(DW)居群单独聚为一支。同时本研究也表明,虽然春兰自交亲和,但在自然界中其繁育系统还是以异交为主。鉴于春兰资源的遗传多样性现状和其相应的居群遗传结构,我们建议在遗传多样性较高的来凤(LF)、京山(JS)、大悟(DW)居群设立保护点进行就地保护;而对资源破坏最为严重的毛坝(MB)和宣恩(XE)居群要实行迁地保护。

Wild Cymbidium goeringii （Orchidaceae） plants in Hubei Province have become endangered due to over-harvesting and habitat fragmentation in recent years. The genetic diversity of 325 individuals from 11 populations in Hubei Province was investigated using inter-simple sequence repeat （ISSR） markers. As a resuit, 127 bands were amplified by 11 informative and reliable primers, of which 112 were polymorphic loci. A relatively high level of genetic diversity was revealed： PPL=88.19%, He = 0.2628, Ho = 0.4037 （at species level）; PPL = 63.06%, He = 0.1945, Ho = 0.2958 （at population level）. A higher level of genetic differentiation was detected among populations with Nei＇s Gsx analysis and analysis of molecular variance （AMOVA; GST= 0.2440, FST = 0.2207）. Some differentiation may result from habitat fragmentation and barriers to gene flow. UPGMA cluster analysis indicated that the five populations from Enshi region （BD, FBS, XE, MB, and LF） grouped together, whereas Dawu （DW） population clustered in an isolated clade. The Mantel test showed that genetic distance was positively correlated with geographical distance. Furthermore, the results showed that a mixed mating system was possibly the main factor influencing the genetic structure of this species. These results, combined with other information about C. goeringii, may provide a valuable basis for proposing conservation strategies. In situ conservation will be suitable for Laifeng （LF）, Jingshan （JS）, and Dawu （DW） populations with sufficient genetic diversity, while an ex situ strategy should be taken into consideration for Maoba and Xuanen populations, where only a few individuals are left.