Wang, S., Xue, J., Ahmadi, N., Holloway, P., Zhu, F., Ren, X. and Zhang, X. 2014. Molecular characterization and expression patterns of PsSVP genes reveal distinct roles in flower bud abortion and flowering in tree peony (Paeonia suffruticosa). Can. J. Plant Sci. 94: 1181-1193. Container culture and flower forcing are used for off-season production of tree peony for the Chinese Spring Festival. Storage of potted tree peony for 10 d at 12°C in a refrigerator before 4°C chilling treatment can help new root growth and promote leaf development. Development from bud swelling to anthesis was divided into nine stages. Some aborted flower buds usually emerge in Stage III. Removal of two to four leaflets in an alternating pattern and applying gibberellic acid 3 (GA₃) around the flower bud at Stage III can decrease the flower bud abortion rate and promote flower formation rate. Two MADS-box genes with homology to Arabidopsis SVP, designated PsSVP1 and PsSVP2, which probably caused flower-bud abortion, were isolated by reverse transcription-PCR. Sequence comparison analysis showed that PsSVP was most similar to SVP-like gene in apple. Phylogenetic analysis indicates that PsSVP was evolutionarily close to SVP-like genes from Malus domestica, SVP genes from Cruciferae and SVP-like genes from Vitis vinifera. The qRT-PCR results suggested that expression of PsSVP was high in vegetative growth phase, especially in the leaves of tree peony, and its expression was regulated by GA₃. Further analysis showed that more PsSVP transcripted in the aborted flower bud, especially in the buds where leaflets grew well. It was deduced that PsSVP can promote vegetative growth and suppress flowering in tree peony. Thus, it is very important to further investigate PsSVP and decipher the mechanisms of flower-bud abortion to improve forcing culture of tree peony.