trnl內含子（trnl intron）及trnl-trnF非轉譯區（trnl-trnF non-codingregion）近年來已成為植物分類的重要工具。本實驗將trnl內含子及trnltrnF非轉譯區用於分辨甜橙以及寬皮柑，發現這兩種柑桔在trnl內含子（trnl intron）之位置有序列上之差異，因此針對此差異設計引子對（primerpair）將其擴增，並將擴增結果進行變性梯度膠體電泳系統（denaturinggradient gel electrophoresis）分析。以此方法對8種市售宣稱100%甜橙果汁進行分析，結果發現全部皆攙有非甜橙類的柑桔果汁。由此可知，變性梯度膠體電泳分析確實可用於甜橙果汁攙假的檢驗。

trnL intron and trnL-trnF non-coding region have become powerful tools to identify plants species in the past few years. In this study, above two regions are used to identify oranges and mandarins via a variable DNA fragment in trnL intron. In order to identify the DNA, a primer pair was designed to amplify the variable fragments and the PCR products were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE). The method successfully detected other citrus juices mixed in all of the falsely claimed 100% orange juices. It is suggested that the method is useful to detect the adulteration of 100% pure orange juices.