Table 4. Calculation of candidate reference genes expression stability by the NormFinder.

Ranking order	Gene	Stability value (Whole stages)	Gene	Stability value (Plain)	Gene	Stability value (plateau)
1	PPIA	0.080	GAPDH	0.032	PPIA	0.076
2	SDHA	0.136	RPL13A	0.057	SDHA	0.166
3	TBP	0.205	ACTB	0.110	ACTB	0.176
4	RPL13A	0.227	PPIA	0.121	RPL13A	0.182
5	18s RNA	0.229	TBP	0.167	18s RNA	0.194
6	β2-MG	0.237	SDHA	0.210	GAPDH	0.237
7	GAPDH	0.265	β2-MG	0.264	β2-MG	0.244
8	ACTB	0.316	18s RNA	0.434	TBP	0.369