Failure of Agrobacterium radiobacter Strain K-84 to Control Crown Gallon Raspberry

Agrobacterium radiobacter (Beijerinc and van Delden) Conn strain K-84 failed to control raspberry (Rubus idaeus L.) crown gall caused by A. tumefaciens (E.F. Smith and Townsend) Conn. Agrobacterium tumefaciens strains isolated from galls on plants that had been treated with K-84 were not sensitive to agrocin 84 in vitro. These strains were isolated from 'Titan' and 'Hilton' raspberry in New York state and from 'Himbo Queen' and 'Schonemann' raspberry in Italy. Almost all strains were identified as A. tumefaciens biovar 2. Raspberry crown gall was not controlled by K-84 in three field experiments in New York state. In two of the experiments, plants were produced by micropropagation and were known to be pathogen-free. The other plant source was shown to be contaminated with the pathogen before treatment with K-84. Crown gall was not controlled either on raspberry in a greenhouse experiment or on Kalanchoe diagremintiana (Hamet. and Perrier) plants that were coinoculated with K-84 and strains of A. tumefaciens isolated from galls on raspberry. Agrobacterium radiobacter strain K-84 is a highly effective biological control of crown gall on certain plant species (Kerr, 1980). K- 84 produces a bacteriocin, agrocin 84, that is an important factor contributing to its biologi- cal control activity (Kerr and Htay, 1974). The sensitivity of A. tumefaciens strains to agrocin