Abstract：The selection of a suitable reference gene is a critical condition for improving the precision of gene expression analyzing by quantitative Real-time PCR (qRT-PCR). In this study, switchgrass(Panicum virgatum L.) root tissues were used as materials. Under different abiotic treatment conditions, mRNA expression stability of ten candidate reference genes, including UBQ1(ubiquitin conjugating enzyme1), ACT2(actin), UBQ2 (ubiquitin conjugating enzyme2), TUB(tubulin), GAPDH(glyceraldehyde-3-phosphate dehydrogenase), CBP20(cap binding protein 20), UCE2(E2 ubiquitin-conjugating enzyme), 18S rRNA1(18S ribsomal RNA protein), NAC(NAC domain protein) and CYP2(cyclophilin) was detected by qRT-PCR technology. Delta-Ct method, Genorm(ver. 3.5), Bestkeeper(ver. 1.0) and NormFinder (ver. 0.953) were used to analyze the all data. The results showed that the most candidate reference genes of switchgrass had some differences in the various abiotic stresses. In the switchgrass root tissues the ranking order of ten reference genes from better to average was as follows: ACT2, TUB, UCE2, CBP20, CYP2, UBQ2, 18S rRNA1, NAC, UBQ1 and GAPDH. Among them, ACT2 gene had the highest expression stability under the drought stress in the root tissue. The 18S rRNA1 gene was the best gene under salt and heat stresses. Under cold and waterlogging stresses, ACT2 was the most comparatively suitable genes. The results of software comprehensive analysis indicated that ACT2, TUB and UCE2 genes were the most stable reference genes which were suitable for switchgrass abiotic stress studies. UBQ1 and GAPDH were not suitable reference genes. The research results can be used for further gene expression study under various abiotic stresses in switchgrass.
