Susceptibility of Paulownia elongata to Agrobacterium and production of transgenic calli and hairy roots by in vitro inoculation

Susceptibility of Paulownia elongata S.Y. Hu (princess tree) to Agrobacterium tumefaciens and A. rhizogenes was demonstrated by inoculating in vitro shoots. Shoots had a gall formation frequency of ≥83% when inoculated with any of three A. tumefaciens strains (542, A281, or C58). Timing of gall appearance and type of callus proliferation differed among A. tumefaciens strains. Rapidly proliferating callus was produced from explants that were inoculated with A. tumefaciens. Hairy roots were produced directly from wound sites on 33% of shoots inoculated with A. rhizogenes strain R1601. Rapidly growing detached roots were produced from explants that were inoculated with A. rhizogenes. Opine analyses demonstrated the expression of foreign genes in proliferating galls/hairy roots shortly after emergence from wound sites and in callus and roots after 12 weeks of in vitro culture. Southern analyses demonstrated the presence of tDNA in long-term callus and root cultures.