VIRULENCE AND SUPERVIRULENCE OF AGROBACTERIUM-TUMEFACIENS IN WOODY FRUIT PLANTS

The ability of two wild-type (C58 and Ach5) and one transconjugant (A2 81) Agrobacterium tumefaciens: strains to incite tumours on some woody fruit species of the Rosaceae, Vitaceae and Rutaceae was determined i n comparison to tobacco and tomato plants. Agrobacterium strain A281 h as been reported to be-supervirulent on tobacco and tomato. Here, the supervirulent phenotype of A281 was clearly shown on tobacco plants bu t not on two different tomato cultivars. On woody fruit hosts, relativ e virulence induced by each Agrobacterium strain was dependent on the infecting strain and the host species. On Rutaceae, A281 showed a supe rvirulent phenotype, while on Rosaceae and on grapevine the responses to all Agrobacterium strains were highly variable and supervirulence w as never observed. It is suggested that different responses observed o n different host species are probably due to the specificity of the Ag robacterium strain-host interaction. Implications of these results for the concept of supervirulence associated with strain A281 and its dis armed derivatives are discussed. (C) 1998 Academic Press Limited.