Cassava embroids derived from friable embryogenic callus of the genotype TMS60444 were bombarded with DNA of the constructs pJIT100 or pJIT64. Both constructs contain the non-invasive reporter gene luciferase from firefly driven by the CaMV 35S promoter. The influence of several particle gun machine parameters and pretreatment of plant material on transient luciferase activity were studied to determine the most essential conditions for stable transformation. Two weeks after bombardment pieces of friable calli with luciferase activity were selected. In total, 67 independent selected calli with luciferase activity (spots), derived from five different experiments, were further cultured either in liquid or on solid medium. Per plate or flask one spot was cultured. In subsequent selection rounds all spots of one individual plate or flask were cultured as one individual group. In this way different transformation events were separated and multiplied.
Eight weeks after bombardment 34 cultures still contained luciferase activity. The mean number of luciferase spots per culture had increased from 1 to 4.6 spots in liquid and to 2.5 spots on solid medium. After two more months of subsequent culture and luciferase selection presence of the construct in these cultures was confirmed at the molecular level using the polymerase chain reaction assay and Southern analysis.
Friable embryos derived from four transformation events were cultured for maturation. Between 3% and 21% of the mature embryos of the different transformation events were luciferase-positive. After multiplication of the luciferase-positive mature embryos by secondary somatic embryogenesis they were germinated. The plantlets analysed contained one to several copies of the inserted DNA. The method presented enables the transformation of this particular cassava genotype, thus allowing the genetic improvement of this important tropical crop by transgenesis.
Raemakers, C.J.J.M.; Sofiari, E.; Taylor, N.; Henshaw, G.; Jacobsen, E.; Visser, R.G.F. Production of transgenic cassava (Manihot esculenta Crantz) plants by particle bombardment using luciferase activity as selection marker. Molecular Breeding (1996) 2 (4) 339-349. [DOI: 10.1007/BF00437912]