CALLUS INDUCTION AND PROTOPLAST ISOLATION FROM TISSUES OF CUCUMIS-SATIVUS L. AND CUCUMIS-MELO L. SEEDLINGS

Hypocotyls, cotyledons and true leaves of in vitro seedlings of 10 cuc umber and melon genotypes resistant to downy and powdery mildew were c ultured on several combinations of initiation and multiplication media to produce callus and subsequently cell suspensions as suitable sourc es for isolation and culture of protoplasts, Cotyledons of both specie s were shown to be the most responsive to variation in culture media. However, calli and cell suspensions derived from hypocotyls generally provided higher number of protoplasts by treatment with several enzyma tic solutions. The protoplasts formed new cell walls after 12 h of cul ture in liquid culture medium and first cell division was observed 2 d later with more frequent divisions after one week of culture.