In Vitro Culture and Somatic Embryogenesis in Cucumis Species
Cucumber (Cucumis sativus) and cantaloupe (Cucumis melo) have been reported to form somatic embryos in vitro. The objective of this study was to establish a protocol for the in vitro culture of several Cucumis spp. and for the induction of embryogenic callus and suspension cultures. In addition to cucumber and cantaloupe, C. metuliferus and C. anguria were included in this study. Leaf discs excised from the first leaf of young plants were placed on Murashige and Skoog (MS) medium supplemented with naphthaleneacetic acid (NAA) and benzylaminopurine (BA) at 1 mg/1. Cultures were incubated at 30 ± 2°C with a 16-hr photoperiod. At 2 to 3 weeks, callus which proliferated from these expiants was placed on media containing a range of NAA and BA concentrations (10−7 to 10−3 M). Optimum callus production and variations in callus morphology, color, and texture were determined. Dense meristematic zones developed under certain regimes. Cucumber seeds were germinated aseptically and various expiants investigated for callus production and regenerative potential on the callus induction medium. Cotyledon expiants regenerated directly with low frequency. Suspension cultures initiated from 5-week-old, root-derived callus developed abnormal embryoids and plantlets after 3 months without a transfer.