不同土层土壤细菌的遗传多样性及其与环境因子的相关性

Genetic diversity of soil bacteria from different horizon and its relationship with environmental factors.

利用RAPD技术分析了浙江省天台山次生灌丛群落不同土层（G1层土深0～5cm、G2层土深5～10cm。G3层土深10～15cm）土壤细菌的遗传多样性及遗传分化．结果显示11种随机引物在27个土壤样品中共检测到168个可重复的位点，G1和G2土层的多态位点百分率均为88．10％，G3土层的多态位点百分率为87．50％，总的多态位点百分率达100％．Shannon信息指数和Nei基因多样性指数估算的不同土层的遗传多样性的高低顺序均为G1〉G2〉G3．不同土层细菌的遗传多样性与可培养细菌数量呈极显著的正相关，与土壤pH值呈显著性正相关，与其它土壤因子的相关性不大．Shannon信息指数与Nei基因多样性指数估算的结果都说明不同土层细菌群落大部分的变异存在于土层内，土层间的遗传分化很低．Nei指数估算的土层问的基因分化系数（Gst）为0．0701，不同土层间具有很高的基因流（Nm=6．63）．AMOVA分子变异分析显示在总的遗传变异中，3．90％的变异发生在土层间。96.10％的变异发生于土层内，土层问的遗传分化不显著（Φst=0．039，P〈0．001）．从土层间的遗传相似度来看，G1与G2两土层的遗传相似度最高．根据土壤细菌不同土层群落间的遗传距离，采用uPGMA法进行聚类，G1土层与G2土层先聚在一起，再与G3土层聚在一起．

Using random amplified polymorphie DNA （RAPD） markers, genetic diversity and genetic differentiation of 3 soil bacterial communites from different horizon （G1 community at 0-5cm horizon, G2 community at 5-10 cm horizon and G3. community at 10～ 15 cm horizon） under secondary scrub on Tiantai Mountain, Zhejiang Province, were analyzed. 168 bands were produced from total 27 samples using 11 random primers. The average per centages of polymorphic loci of G1 and G2 community was 88. 10%, while that of G3 community was 87. 50%, The total percentage of polymorphic loci of soil bacteria communities from 3 different horizon was 100%. Among 3 bacterial communities, Net＇s gent diversity and Shannon＇s information index showed that G1 community exhibied the highest level of variablility, while G3 community gave the lowest. Genetic diversity was exstreamly positively corre lated with the cultured bacteria count and significantly positively correlated with pH value of soil. No correlation was observed with the other environmental factors. Net＇s gene diversity and Shannon＇s information index indicated that the great majority of genetic variation resided within communities and the genetic differentiation was low among communities. Coefficient of gene differentiation （Gst） was only 0. 070 1. The gene flow among soil at different horizon was very high （Nst=6.63）. The AMOVA program was used to analyse the molecular variance and showed that there was no significant difference among soil bacterial communities（Φst=0. 039, P〈0. 001）. The among-popula tion component accounted for only 3. 90% of the total variation, while the within population component, accounted for 96.10%. The genetic similarity between G1 and （2-2 community was the highest. UPGMA （unweighted pair group method arithmetic average） clustering was conducted and the results showed that G1 and G2 community were clustered into one group first, then G3 community clustered together.