design: Total RNA was isolated from leaves harvested at 50 d and 60 d, using an RNAprep Pure Plant Kit with three replicates. The RNA integrity and quality were confirmed by gel electrophoresis and using a NanoDrop 2000 spectrophotometer. Twenty micrograms of RNA were separately pooled from the twelve samples for cDNA library preparation. The residual RNA was used for qRT-PCR.