Abstract: To investigate the mechanism of russet skin formation in‘Xiusu’pear, the sport of Chinese pear‘Dangshan Suli’（Pyrus bretshneideri Rehd.），the lignin content and activities of Phenylalanine ammonia-lyase （PAL），4-hydroxycinnamate Co-A ligase（4CL），Cinnamyl alcohol dehydrogenase（CAD） and Peroxidase（POD）related to lignin biosynthesis, in pericarp of‘Dangshan Suli’and‘Xiusu’pear at 25，50，75，100，125，150 and 175 days after full bloom were tested by spectrophotometry，respectively. From the positive SSH-cDNA library of‘Xiusu’pear，CCoAOMT-EST was screened out and the relative quantity of its expression was analysed by Real-time PCR. The results showed that there were three peaks of lignin increment in the pericarp of‘Dangshan Suli’pear，and lignin accumulation was 12.2%higher in ‘Xiusu’than that in‘Dangshan Suli’pear when the fruit matured. The activities ofPAL，4CL，CAD in pericarps of‘Xiusu’and‘Dangshan Suli’pear all reached to the maximum at 75 days after full bloom，which of POD attained the maximum at 125 days after full bloom. Although the trends of the four enzymes dynamic change in‘Xiusu’were similar as those in‘Dangshan Suli’pear，their activities in the former were higher than in the later. There was positive significant correlation between PAL or 4CL activities and ligninincrement in‘Xiusu’but not in‘Dangshan Suli’pear. As the fruit developed，the relative quantity of CCoAOMT expression at each stage in the pericarp of‘Xiusu’was evidently higher than that of ‘Dangshan Suli’pear. It was postulated that the mechanism of russet skin formation in‘Xiusu’pear was related to lignin accumulation and the relevant enzyme activity enhancement，and the expression increment of CCoAOMT gene may be a key factor contributed to the russet skin formation of‘Xiusu’pear.

Key words: pear, fruit skin color, lignin, enzyme activity, CCoAOMT gene, Real-time PCR