Virulence and supervirulence ofAgrobacterium tumefaciensin woody fruit plants

Abstract

The ability of two wild-type (C58 and Ach5) and one transconjugant (A281)Agrobacterium tumefaciensstrains to incite tumours on some woody fruit species of the Rosaceae, Vitaceae and Rutaceae was determined in comparison to tobacco and tomato plants.Agrobacteriumstrain A281 has been reported to be supervirulent on tobacco and tomato. Here, the supervirulent phenotype of A281 was clearly shown on tobacco plants but not on two different tomato cultivars. On woody fruit hosts, relative virulence induced by eachAgrobacteriumstrain was dependent on the infecting strain and the host species. On Rutaceae, A281 showed a supervirulent phenotype, while on Rosaceae and on grapevine the responses to allAgrobacteriumstrains were highly variable and supervirulence was never observed. It is suggested that different responses observed on different host species are probably due to the specificity of theAgrobacteriumstrain–host interaction. Implications of these results for the concept of supervirulence associated with strain A281 and its disarmed derivatives are discussed.