TUMOR-FORMATION BY AGROBACTERIUM-TUMEFACIENS IS SUPPRESSED BY AGROBACTERIUM-RADIOBACTER HLB-2 ON GRAPE PLANTS

Agrobacterium radiobacter HLB-2 inhibits Agrobacterium tumefaciens in vitro and tumor development on grape stem explants. The suppression of tumor formation was more effective when HLB-2 was inoculated either p rior to a virulent strain or simultaneously, and at a higher cell conc entration. Grape explants were transformed 0 to 48 hours after woundin g (conditioning). Both A. radiobacter strains HLB-2 and K84, and A. tu mefaciens strains are able to multiply similarly in grape explants. Th e ability of HLB-2 to suppress tumors does not appear to be merely a r esult of competition for nutrients.