【摘要】 本文通过对杨属5组代表种并以柳属中旱柳的ITS序列作为参照,用成对比较的方法对杨属21个植物样品的ITS序列比较发现,杨属ITS序列的碱基替换情况是转换数大于颠换数,ITS-1序列中碱基发生转换和颠换的数目基本相似,而ITS-2序列中碱基发生转换的数目远远大于颠换。用朱克斯和坎托一参数模型和木村二参数模型对杨属ITS序列的替换率计算,无论是ITS-1还是ITS-2序列都没有达到数理统计上的明显差异。但由于ITS-2序列碱基的变化转换大大高于颠换,所以二参数模型计算所得结果大于一参数模型;采用相对速率测验法,对杨属各组分子进化相对速率进行了检测,结果分析得知,杨属5组的ITS序列分子进化速率有差异。杨属各组的ITS-1序列比较说明,大叶杨组、青杨组、黑杨组的进化速率都小于白杨组,而胡杨组则是进化速率最快的,大叶杨组的进化速率小于青杨组、胡杨组和黑杨组,黑杨组和胡杨组大于青杨组;ITS-2序列比较发现白杨组是进化速率最慢,其次是大叶杨组、青杨组,而黑杨组则稍大于胡杨组;总ITS序列比较是大叶杨组和黑杨组相对较慢,胡杨组最快;但就总的碱基替换分析,除了黑杨组和大叶杨组在ITS-1区间及青杨组、胡杨组和白杨组在ITS-2区间进化速率有显著差异外,其余组间都无显著的差异,尤其是在整个ITS序列区段碱基替换的差异都无显著差异。更多还原

【Abstract】 This paper analyzed molecular evolution characteristics of ITS sequences from 21 examples of 5 sections of Populus by sequence comparison method. Compared to the ITS sequence of Salix matsudana, it indicates there are more transition ratios than transversion ratios that come into being in those ITS base substitutions; In ITS-1 the numbers of base transition are almost same to base transversion; But there are more base transition ratio took place than base transversion. And there is not distinct difference of base substitutions in ITS-1 or ITS-2 after calculated based on Juks & Cantor’s One Parameter Model and Kimura’s Two Parameter Model in statistics. The numerical values calculated by Two Parameter Model are larger than by One Parameter Mode, due to more transition ratio than transvertion ratio in ITS-2. The results from Relative Rate Test showed that different sections of Populus had different base evolution rate based on different ITS sequences regions analyzed. In ITS-1 sequences, the evolution ratio of Leucoides, Tacamahaca and Aigeiros are slower than Leuce’s, Turanga has the fastest molecular evolution rate in Populus, and Leucoides’ rate is slower than Tacamahaca, Aigeiros and Turanga’s. But in ITS-2 sequences analyzed, Leuce has the slowest evolution rate in Populus, Tacamahaca & Leucoides also have a slower evolution rate relatively, and Aigeiros’s rate has a little faster than Leucoides’s. There is the fastest evolution rate in Turanga, Aigeiros and Leucoides have relative slow evolution rates in all sections based on complete ITS sequence analyzed. Nevertheless, there is not distinct difference based on total base substitutions but between Aigeiros and Leucoides in ITS-1 region and among Tacamahaca, Turanga and Leuce in ITS-2 region.更多还原