Abstract: The dynamics of fruit developing， accumulation of fruit sugar components and activities of sucrose metabolizing related enzymes were studied in red bayberry during the period from 54 d after blossoming (DAB) to mature by using three varieties， Myrica rubra cv Dongkui， M rubra cv Heijing and M rubra cv Wenlingdamei Results indicated that the fruit sugar components were dominated by sucrose， fructose and glucose Sucrose was the maximum sugar component， about sharing 40%-50% of the total sugar The content of the three components firstly performed a slight decline， and then followed a rapid accumulating till to mature At mature time， the contents of all the three sugar components reached their summits， were 34.4-48.9， 24.6-28.6 and 23.2-27.7 mg·g-1 FW， respectively The titratable acid contents rose first， then decreased and reached the bottom at full mature time during fruit developing， which was 0.44%-0.62% The activities of sucrose metabolizing enzymes， including acid invertase (AI)， neutral invertase (NI) and sucrose synthase (decomposing direction， SSD) showed a similar trend Their activities declined first to low level， then rose gradually and got to their highest at full mature time, they were 40.3-52.8， 31.2-40.5 and 3.5-4.0 mg glucose · g-1 FW， respectively The order of enzyme activity from high to low was： NI > AI > SSD It was probably supposed that the high activity of NI and AI was a main promoter for the accumulation of fructose and glucose in Chinese bayberry fruit at harvesting time The activity of sucrose synthase (synthesizing direction， SSS) and sucrose phosphate synthase (SPS) changed differently in M rubra cv Dongkui fruits Both of them reached their highest activity at full mature time， but the activity of SSS was higher than that of SPS They were (53.4±2.4) and (35.8±2.8) mg sucrose · g-1 FW， respectively It probably implied that the high SSS and SPS activity was a main reason of sucrose accumulation in ripe red bayberry fruit， and SSS activity distributed more than that of SPS.

Key words: red bayberry (Myrica rubra), fruit, sugar component, sucrose metabolizing enzymes