GENETIC-TRANSFORMATION OF WHEAT MEDIATED BY AGROBACTERIUM-TUMEFACIENS

A rapid Agrobacterium tumefaciens-mediated transformation system for w heat was developed using freshly isolated immature embryos, preculture d immature embryos, and embryogenic calli as explants. The explants we re inoculated with a disarmed A. tumefaciens strain C58 (ABI) harborin g the binary vector pMON18365 containing the beta-glucuronidase gene w ith an intron, and a selectable marker, the neomycin phosphotransferas e II gene. Various factors were found to influence the transfer-DNA de livery efficiency, such as explant tissue and surfactants present in t he inoculation medium. The inoculated immature embryos or embryogenic calli were selected on G418-containing media. Transgenic plants were r egenerated from all three types of explants. The total time required f rom inoculation to the establishment of plants in soil was 2.5 to 3 mo nths. So far, more than 100 transgenic events have been produced. Almo st all transformants were morphologically normal. Stable integration, expression, and inheritance of the transgenes were confirmed by molecu lar and genetic analysis. One to five copies of the transgene were int egrated into the wheat genome without rearrangement. Approximately 35% of the transgenic plants received a single copy of the transgenes bas ed on Southern analysis of 26 events. Transgenes in T-1 progeny segreg ated in a Mendelian fashion in most of the transgenic plants.