Plant Regeneration from Embryos of Cucumis Metuliferus Cross-Pollinated with Cucumis Anguria
The African-horned cucumber (Cucumis metuliferus Naud.) and the West India gherkin (C. anguria L.), both carrying resistance to root-knot nematodes (Meloidogyne spp.), were cross-pollinated successfully with C. metuliferus as the female parent. Embryo development was abnormal and arrested in the “rabbit-ear” stage. Occasionally, mature embryos were recovered, but they did not germinate on nutrient media tested. Presumptive hybrid plants were cultured on a basal medium containing Murashige and Skoog (MS) salts, vitamins, m-inositol (100 mg/1), casein hydrolysate (1 g/1), and sucrose (30 g/1), supplemented with indole-3-acetic acid (IAA) (5 and 10 μM) and N6-benzyladenine (BA) (5 and 10 μM), and solidified with purified agar (7 g/1). Cultures were incubated at 25°C in the dark for 7 to 14 days, transferred to 16 hr of low light (50 fc) for 5 days, and then transferred to high light (750 fc). Embryoids and leaflets differentiated on the hybrid embryo cotyledons on media containing IAA/BA (5/10, and 10/5 μM). Leaflets from 10/5 μM IAA/BA were converted to whole plants by 2 successive subcultures on 1/3 MS and 1% sucrose. The hybrid plants were abnormal and contained flattened stems with short internodes surrounded by multiple small leaves. They were chlorophyll-deficient and did not grow to maturity after transplanting to a soil mix. Further work is in progress to increase the efficiency of converting hybrid embryos to plants via plant regeneration of embryos in culture.