MOLECULAR WHEAT BREEDING BY DIRECT GENE-TRANSFER

A method for efficient genetic transformation of wheat has been develo ped using immature embryos as targets for microprojectile-mediated gen e transfer and a helium driven particle delivery system. Screening and selection of transgenic cells, somatic embryos and regenerated plants are performed with the gus-gene and the phosphinothricin acetyl trans ferase (bar) gene coding for Basta-resistance as the selectable marker . On average, one fertile transgenic plant can be obtained from about 100 microprojectile treated, immature embryos. The number of integrate d copies of the transferred gene ranges from 1 up to about 10. Stable integrated genes are inherited in most of the transgenic lines in a no rmal mendelian fashion segregating 3:1 in the F-2. Homozygous, as well as heterozygous,lines have been followed and analysed genetically at the molecular level and up to F-5. Apart from normal stable gene expre ssion, examples have also been found which showed a loss of gene activ ity or unexpected segregation pattern. For applied aspects, different genes are transferred aiming for improved disease resistance, modifica tion of quality, or other characteristics. First results from these tr ansgenic lines are reported, and problems still existing with the prod uction of stable transgenic wheat lines are discussed.