Abstract: To screen the dwarf trait related genes，the shoot length and internode length of 12 pear varieties or selections with different plant architectures were measured during the new shoot growth period. The genes differentially expressed in the growth points，leaves and phloem among three pear varieties ‘Zaosu’（vigorous），‘Jinxiang’（semi-dwarf）and‘Zhongai 1’（dwarf）at different periods were screened by transcripome sequencing analysis. Combined with the expression verification in new shoot phloem of 12 varieties or selections，dwarf trait related candidate genes were obtained. One of the candidate genes PcGA2ox2 was overexpressed in tobacco to analyze its function. The results showed that the new shoot length of‘Zaosu’，‘Jinxiang’and‘Zhongai 1’had a slight difference in the early growth period，while showed a significant difference in the middle and late growth period of new shoot. The internode length of dwarf varieties were shorter than that of vigorous varieties in all test periods. The shoot length and internode length of six vigorous varieties were significantly longer than those of six dwarf or semi-dwarf varieties or selections in the middle and late growth period of new shoot. The number of differentially expressed genes between two samples ranged from 1 882 to 5 729 in different tissues，and periods of three varieties. Among them，51 differentially expressed genes showed an increase or decrease in expression levels with the decrease of new shoot length in both leaf and phloem. Nine differentially expressed genes in new shoot phloem of three varieties were selected to verify the expression levels by RT-qPCR in the phloem of 12 pear varieties or selections in the late growth period of new shoot. Among them，four genes showed a tendency of significant higher or lower expression in dwarf varieties or selections than that in vigorous varieties or selections，and were identified as candidate genes related to dwarf trait. One of the dwarf candidate genes was a member of GA2ox family genes. Total 15 members of the GA2ox gene family were further identified in the‘Zhongai 1’genome，and the expression of the candidate PcGA2ox2 gene was significantly higher in new shoot phloem of dwarf varieties or selections than that of vigorous varieties. Then PcGA2ox2 gene was overexpressed in tobacco，the transformed plants were significantly smaller than the control plants. In conclusion，PcGA2ox2 gene plays a key role in the dwarf trait of‘Zhongai 1’pear.

Key words: pear, dwarf, transcriptome analysis, gibberellin, PcGA2ox