Objective  In search for internal reference genes of Cucumis melo L. that could stably express in different tissues and under stress conditions to warrant accuracy and reliability of the RT-qPCR analysis on target gene expression.

  Method   Expression stabilities of 9 candidate genes, 18srRNA, TUA, EF1a, Actin1, Actin2, Actin3, Actin4, CYC, and UBI-ep, from the roots, leaves, seeds, and fruits of Xinyinhui melon being treated by water, cinnamic acid, saline alkali or ABA were determined by RT-qPCR and analyzed using the BestKeeper, NormFinder, and geNorm software.

  Result   In different tissues, the top 5 choice genes identified by BestKeeper ranked as CYC＞18s rRNA＞UBI-ep＞EF1a＞TUA, those by NormFinder EF1a＞UBIep＞Actin4＞CYC＞Actin3, and those by geNorm Actin4=Actin3＞Actin1＞EF1a＞UBI-ep. Under various stresses, they were 18s rRNA＞Actin3＞Actin4＞EF1a＞UBI-ep as ranked by BestKeeper, EF1a＞UBI-ep＞Actin4＞CYC＞18s rRNA by NormFinder, and EF1a=UBI-ep＞Actin4＞CYC＞Actin by geNorm. Overall, EF1a appeared to be most stable among the 9 genes. Insofar as variety of tissues is concerned, Actin4, Actin3, Actin1, and EF1a were more stable than the others; and, under stress, EF1a and UBI-ep tended to be superior.

  Conclusion   Stably expressed in the tissues under the stresses as tested, EF1a was selected as the reference gene for studies on C. melo to reduce experimental errors. To further ensure accuracy, application of dual reference genes in RT-qPCR analysis might be considered.