Selective media for three biovars of Agrobacterium

Three selective media for the isolation of the three known biovars of Agrobacterium are described. Selectivity was based on carbon and nitrogen sources; L(—)‐arabitol for biovar 1, erythritol for biovar 2 and a combination of tartrate and D‐glutamate for biovar 3. The new media were compared with existing selective media. Recovery of agrobacteria from soil was very efficient and discrimination between the three biovars was satisfactory except for tartrate‐utilising biovar 1 isolates which grew on the biovar 3 medium. Some strains of Pseudomonas sp. isolated from crown galls on vine could utilise octopine as a source of carbon and nitrogen.