INDUCTION OF NODULE-LIKE STRUCTURES ON OILSEED RAPE BY INOCULATION WITH RHIZOBIA IN THE PRESENCE OF HELPER BACTERIA

Nodule-like structures on the roots of seedlings of oilseed rape (Bras sica campestris L. subsp. napus) cv. CO were induced by Bradyrhizobium sp. strain CP283 or A(2)P(5) in the presence of Erwinia carotovora MA FF-301393, a bacterium that produces the cell wall-degrading enzymes c ellulase and pectinase. E. carotovora was most effective at an inocula tion density of 2.0 x 10(8) cells plant(-1). Lower densities decreased the rate of nodule-like structure formation, while higher densities c aused plant death. The induced nodule-like structures were either sphe rical or elongated. Histological sections of the structures showed a d istinct central vascular cylinder and a surrounding swollen region com posed entirely of cortical cells. The highest rate of nodule-like stru cture formation (33.3%) was achieved by combined inoculation of B. sp. strain CP283 and E. carotovora.