Agrobacterium radiobacter Strain K1026, a Genetically Engineered Derivative of Strain K84, for Biological Control of Crown Gall. D. A. Jones, Research Associate, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064. A. Kerr, Professor, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064. Plant Dis. 73:15-18. Accepted for publication 28 June 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0015.

Agrobacterium radiobacter strain K1026 was tested in open-air pot trials, in comparison with strain K84, for its efficacy in controlling crown gall on almond seedlings. Seedlings aged 2 and 10 mo were dipped in water or a suspension of K1026 or K84, planted in soil infested with Agrobacterium tumefaciens strain K27, and grown for 7 mo. Galls were absent or rare on the roots of seedlings that had been treated with K1026 or K84. In contrast, the roots of seedlings treated with water had from 3 to 23 galls per plant for 2-mo-old seedlings and from 13 to 103 galls for 10-mo-old seedlings. There was no significant difference in gall incidence between plants treated with K1026 or K84, indicating that K 1026 is as effective as K84 in controlling crown gall. Because K 1026 is unable to transfer its agrocin-84 plasmid to pathogenic agrobacteria, it should be used as a replacement for K84 to prolong the effective biological control of crown gall. The registration of K 1026 as a pesticide would seem to be justified and applications for such registration have been submitted.