Table 2. Ranking order of the candidate reference genes by four programs: geNorm, NormFinder, BestKeeper and ΔCt.

Rank	geNorm		NormFinder		BestKeeper		ΔCt
	Gene	Stability (M)	Gene	variability	Gene	CV (%Ct)	Gene	Mean SD
1	U6/TPB	0.172	GAPDH	0.066	GAPDH	0.44	GAPDH	0.322
2			U6	0.132	TPB	0.95	B2M	0.352
3	GAPDH	0.249	TPB	0.145	U6	1.08	U6	0.359
4	B2M	0.275	B2M	0.147	B2M	1.3	TPB	0.364
5	Rpl13A	0.291	ppIA	0.199	ppIA	1.59	Rpl13	0.393
6	ppIA	0.312	Rpl13A	0.207	Rpl13A	1.61	YWHAZ	0.408
7	YWHAZ	0.357	YWHAZ	0.294	YWHAZ	1.74	ppIA	0.415
8	18s rRNA	0.409	18s rRNA	0.347	18s rRNA	2.77	18s rRNA	0.595

M: the mean expression stability values; CV: the coefficient of variance; Mean SD: mean standard deviation.