Abstract:A cDNA library was constructed and characterized from the pulp of Cara Cara navel orange (Citrus sinensis Osbeck) at different stages of ripening. Tittering results revealed that approximately 5.086×105 independent clones were included in this library. Electrophoresis gel results of 15 randomly selected clones revealed that the size of the insertion fragments ranged from 400 bp to 2 kb, with an average size of 900 bp. Sequencing results of 150 randomly picked clones showed that the recombination rate was 94%. During subsequent sequence analysis, 41 of 139 clones failed to be identified and the amino sequence of 71 clones shared less than 30% identity with related plants in GenBank. Of 27 clones whose amino sequences shared more than 60% identity with other related plants in GenBank, 17 clones showed an 80% identity with the corresponding candidate genes of citrus. The clone recognized as the type III metallothionein-like (MT) gene was observed to occur 13 times, indicating that the protein may play an important role in fruit development and ripening.(Author for correspondence.Tel: 027 8728 1712; Fax: 027 8728 0016; E-mail: xxdeng@mail.hzau.edu.cn)