TRANSFORMATION OF MEDICAGO-ARBOREA L WITH AN AGROBACTERIUM-RHIZOGENES BINARY VECTOR CARRYING THE HYGROMYCIN RESISTANCE GENE

Plants of Medicago arborea have been infected with Agrobacterium rhizogenes stain LBA9402 harbouring the plasmids Ri 1855 and AGS125 carrying a gene conferring resistance to the antibiotic hygromycin. About 70% of the hairy roots showed callus formation on hygromycin-supplemented medium. Regeneration took place on antibiotic free medium only. Plantlets suitable for transfer to soil were obtained after the manual removal of most of the leaves. Plant morphology showed the usual alterations induced by the Ri plasmid; moreover, two years after soil-transfer, transformants have not flowered. Molecular analysis indicates the presence of T-DNA from both pAGS125 and p1855. The expression of the hygromycin phosphotransferase gene allowed callus and protoplasts of transformed plants to grow on media supplemented with the antibiotic. This trait will be utilized as a marker in protoplast fusion between Medicago arborea and Medicago sativa (alfalfa).