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Induction of Resistance Towards Bacterial Pathogens of Tomato by Exposure of the Host to Dinitroaniline Herbicides. R. Cohen, Newe Ya’ar Experiment Station, Post Haifa 31-999, Israel; D. A. Cuppels(2), R. A. Brammall(3), and G. Lazarovits(4). (2)(4)Agriculture Canada, London Research Centre, 1400 Western Road, London, Ontario, Canada N6G 2V4; (3)Horticultural Research Institute of Ontario, Horticultural Experiment Station, Box 587, Simcoe, Ontario, Canada N3Y 4N5. Phytopathology 82:110-114. Accepted for publication 16 September 1991. Copyright 1992 Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-82-110.

Growth of tomato seedlings (cv. Bonny Best) in rooting substrate amended with the dinitroaniline herbicide, dinitramine (1 ppm in sand/Pro-mix, 1:1 or 1:2, v/v), caused a suppression in bacterial wilt symptoms caused by the Pseudomonas solanacearum strain K60. Dinitramine was not inhibitory to P. solanacearum in in vitro assays nor did it restrict multiplication of the pathogen in treated plants. Dinitramine also caused a decrease in the severity of bacterial canker, caused by Clavibacter michiganense subsp. michiganense JD83-1, but had no significant effect on the severity of bacterial speck, caused by Pseudomonas syringae pv. tomato DC894H. Resistance was not induced by a similar exposure of plants to the herbicides ethalfluralin or oryzalin. Resistance to Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici, was induced by exposure of seedlings to the herbicides dinitramine, ethalfluralin, and oryzalin. Acetochlor induced resistance towards Fusarium wilt but did not towards bacterial wilt. Exposure of plants to the dinitroaniline herbicide, trifluralin, did not induce resistance towards either bacterial wilt or Fusarium wilt in our experiments.