Callus induction and protoplast isolation from tissues of Cucumis sativus L. and C-melo L. seedlings

Hypocotyls, cotyledons and true leaves of in vitro seedlings of 10 cucumber and melon genotypes resistant to downy and powdery mildew were cultured on several combinations of initiation and multiplication media to produce callus and subsequently cell suspensions as suitable sources for isolation and culture of protoplasts, Cotyledons of both species 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 enzymatic solutions. The protoplasts formed new cell walls after 12 h of culture in liquid culture medium and first cell division was observed 2 d later with more frequent divisions after one week of culture.