重金属污染下曼陀罗种群分化的RAPD分析

将不同空间地段上获得的同一种质但污染年代各不相同的4个曼陀罗材料种子易地种植在同一模拟重金属污染生境中，对这4个曼陀罗种群进行RAPD分析，结果表明，在105个检测位点中发现有78个位点呈多态性。在这些多态位点中未发现与重金属抗性有关的特异性多态DNA片段。S hannon-Weiner指数计算结果表明，在短期污染时间内曼陀罗种群遗传多样性水平降低。随着污染时间的推移，曼陀罗种群逐渐在污染迹地上稳定下来，曼陀罗种群遗传多样性水平有所回升和提高，4个曼陀罗种群遗传多样性由高到低排列顺序为L＞CK＞M＞S。遗传多样性指数表明曼陀罗种群间变异程度远小于种群内的遗传变异。4个种群两两间遗传距离较小，遗传距离最大的种群为L和S，最小的为L和CK种群。因此，在重金属胁迫环境选择下，曼陀罗种群发生了一定程度的分化与微进化，轻高水平的遗传多样性可能是植物适应重金属污染胁迫环境的基础。

Differentiation in Datura stramonium L. populations exposed to heavy-metal pollution at different durations: RAPD analysis

Four Datura stramonium L (abbreviated as D S in context) populations were selected in the pesent study for genetica analysis. The populations with the identical germ plasm virgin and different duration of exposure to the pollutants had continually grown in similar heavy metal polluted soils,including a control, CK, a short termed exposure S,a medium termed exposure M, and a long termed exposure L The seeds from the three D S populations (S, M, and L)as different treatments were planted in a simulated heavy metal polluted soil The seeds from CK were planted in a normal soil By means of RAPD, DNA polymorphisms and genetic diversity among D S populations and within populations were analyzed The result of RAPD analysis (with 31 random primers selected from 160 primers) showed that 78 polymorphic RAPD loci were detected from among 105 loci, and no specific band related to resistance to heavy metal was found During the initial pollution period, the genetic diversity decreased With time, a higher level of DNA diversity was detected in L population than that in CK The genetic diversity followed the orders L > CK > M > S by Shannon Weiner index The value of genetic distance among populations was low DNA data also showed that the differentiation degree of DNA polymorphism among populations was much lower than that within a population A cluster analysis (N J Method) based on genetic distance was used to investigate genetic relationship between the four populations It demonstrated a genetic differentiation between L and S populations It is assumed that the high level of genetic diversity was possibly responsible to the adaptation of D S to heavy metal polluted environment