Genetic transformation of Lotus corniculatus with Agrobacterium tumefaciens and the analysis of the inheritance of transgenes in the T ₁ generation

The herbage legume,Lotus corniculatus (bird's-foot trefoil), was transformed using the disarmedAgrobacterium tumefaciens strain LBA4404 (pAL4404) carrying a binary construct, pJit73. This plasmid carries two antibiotic resistance genes,aphIV andnptII encoding resistance to hygromycin and kanamycin respectively, and the easily detectable reporter gene,uidA encoding the enzyme β-glucuronidase (GUS). Transgenic plants were regenerated from two separate co-cultivations of leaves withA. tumefaciens either with or without an acetosyringone pretreatment. A total of 110 putative transformants were regenerated, 52 (47%) of which grew on selection media containing hygromycin. Twenty-five plants were analysed further for morphological variation and presence of transgenes and were used to study the inheritance of expression of the transgenes in the T1 generation. Expression patterns of the transgenes in the T1 progeny generated from these 25 plants differed. In the majority of plant linesaphIV anduidA transgenes segregated together, but the apparent number of copies of the transgenes varied. No expression of either transgene was detected in the progeny from three plants, while the progeny from six other plants were resistant to hygromycin but had no GUS expression. Progeny of all of the remaining 16 plants had GUS activity. For three plants, inheritance data were consistent with more than one dose ofuidA andaphIV; another two plants yielded data expected for exactly one dose of both transgenes. In the progeny of the remaining 11 plants, the percentage of seedlings expressing bothuidA andaphIV was lower than expected