Induction of Tumours by Various Strains of Agrobacterium tumefaciens on Abies nordmanniana and Picea abies

Abies nordmanniana and Picea abies seedlings were inoculated with a wild-type (C 58) or an attenuated strain (rooter or shooter mutants) of Agrobacterium tumefaciens. Large tumours were formed on A. nordmanniana in response to the wild-type and rooter strains, 60-65 % of the seedlings being susceptible. Smaller tumours were formed on Picea abies in response to the wild-type strain, at least 12% of the seedlings being susceptible. Tumours from both species induced by the wild-type strain grew in vitro on medium without added phytohormones.