TUMOR INDUCTION IN VICIA FABA AND OTHER HOSTS BY AGROBACTERIUM RUBI (HILDEBRAND) STARR AND WEISS

Abstract

In a search for suitable material for a cytological study of plant tumors, pure and virulent cultures of A. tumefaciens were inoculated into stems of young Vicia faba plants without result. On the other hand, a bacterium isolated from Himalaya blackberry produced large tumors. A comparison of the 2 forms as to their virulence on other plant species showed that the blackberry organism would not attack tomato. Nicotiana glutinosa and Datura medeioides are all highly susceptible to A. tumefaciens. Sunflower proved to be a common host to the 2 pathogens, but the tumors caused by the blackberry organism were smaller and were not accompanied by epinasty of the leaves immediately above the tumor, a characteristic feature associated with tumor formation induced by A. tumefaciens. From cultural characters and differences in host range, it was decided that the blackberry organism belongs to A. rubi, a species considered as confined to Rubus spp. Its host range is obviously much wider than this and, as it embraces plants only slightly or not at all susceptible to A. tumefaciens, it is likely to prove an important addition to this species in providing material for the study of plant tumors.