为了研究分离获得的引发桔子霉烂的优势真菌指状青霉提取物的致突变作用。方法：将Ｅ．ｃｏｌｉ ｋ１２菌株作为诱变对象，利用ＰＣＲ扩增得到ｉｎｆＡ基因片段，通过Ｔ载体克隆并作序列分析。结果：ｉｎｆＡ基因片段中 有５个点突变存在；推导氨基酸序列有一个氨基酸变异（Ｌｙｓ→Ｖａｌ）。结论：指状青霉提取物可引起 Ｅ．ｃｏｌｉ ｋ１２菌株 基因突变。 In order to study the mutagenicity of the isolated extract of Penicillium funiculosum which is the dominant fungus causing orange rot. Method: E. coli k12 strain as a mutagenized object, the infA gene fragment was amplified by PCR and cloned by T vector and sequenced. Results: There were five point mutations in the infA gene fragment; one amino acid mutation was deduced in the amino acid sequence (Lys → Val). Conclusion: Penicillium expansum extract can cause E. coli coli k12 strain gene mutation