球壳孢目真菌DNAGC含量及其分类学意义

DETERMINATION OF THE GC CONTENT OF DNA AND ITS TAXONOMIC SIGNIFICANCE IN SPHAEROPSIDALES

利用热变性温度法测得球壳孢目5属14种19个菌株DNAG十Cmol％的变化范围为48．08～53．7，平均值为51.12，与文献报道的丝孢菌类的平均值接近，也与子囊菌的平均值相差不大，提示该类群的种类及其与大多数丝孢菌间在系统演化上似具一定的同源性，与形态分类对半知菌的处理相吻合，也为其有性阶段大多属子囊菌这一事实提供了佐证；各属、种GC值接近，且相互间有交叉，种内菌株间差异小于2％，方差分析显示属间差异不显著，故认为GC含量分析不宜用于球壳孢目属、种级分类单位的划分，但可作为排除性指标辅助某些种类的否定性判定。

The DNA GC contents of 19 isolates from 14 species belonging to 5genera of Sphaeropsidales were inveshgared by the method of thermal denaturationtemperature. The result showed that the GC content of DNA from Sphaeropsidales isin a narrow variance range of 48.08- 53.7%, with a higher average value of 51.2.The total span of 5.62% revealed that species of this fungal group Possess an identicalgenetic background to a certain extent and supposed the treatment of groupingtogether species of Sphaeropsidales on the basis of morphology. The higher level ofaverage GC content which aPProaches to average GC content of species ofascomycetes reported in literature provided a suPPlementary evidence for the fact thatthe known sexual generations of SPhaeropsidales mostly belong to ascomycetes. Theinterspecific diversity of the base composition was quite small in genus, and theoverlaPPing variance ranges of G+ C mol% were present among genera. Thus, it wassuggested that the GC content of DNA may be regarded as an assistant norm to theexclusion of a certain individual from some taxa but it can not be used fordistinguishing species or genera in SPhasropsidales.