Abstract: The effects of the five commonly used buffers on DNA nuclei isolation from fruitlet of litchi were evaluated. The results showed that improved method on Otto buffers（adding the content and type of reducing agent into Otto buffers，putting RNase A directly into the buffer and reducing the centrifugal force）could get the highest resolution and the lowest coefficient of variation G1/G0 peak of DNA nucleus，which was suitable for detecting the cell division activity of litchi fruitlet and pericarp. By comparing with cell division activities of fruitlet and pericarp in the first stage of fruit development between larged-fruit and smalled-fruit from the early and late flowering flowers of‘Feizixiao’litchi with the similar genetic background，and from‘Siliangguo’and‘Chenzi’litchi with the different genetic background respectively，it was found that the cell division activity of larged-fruit was higher and lasted longer compared with the smalled fruit，indicating that their differences in terms of the final fruit size was related to the cell division activity in early fruit development.

Key words: litchi, cell division activity, flow cytometry, fruit size, nuclei suspension