Somatic embryogenesis and plant regeneration from immature cotyledons of watermelon

Cotyledon expiants from immature embryos of five watermelon Citrullus lanatus (Thunb.)Matsum. & Nakai] genotypes were incubated in the dark for three weeks on a modified MS medium containing B5 vitamins, 2,4-D (10, 20 or 40M), 0.5 M of either BA or TDZ, and 7 g·1^-1 TC agar. Somatic embryos, some with well developed cotyledons, were observed on cotyledon expiants three to four weeks after transfer to MS medium without PGRs and 16h photoperiod. The best PGR combination for somatic embryogenesis was 10 M 2,4-D and 0.5 M TDZ Somatic embryogenesis was greatest (30%) when cotyledon expiants were established from 18-day-old immature embryos. Somatic embryos were germinated on MS medium without PGRs. Plants were transferred to Magenta boxes containing ProMix for three weeks before being transplanted to the field where they formed fertile male and female flowers that produced normal fruit.Abbreviations PGR plant growth regulator - BA benzyladenine - TDZ thidiazuron - 2,4-D 2,4-dichlorophenoxyaceticacid - NAA -naphthaleneacetic acid - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid