A Greenhouse Method for Selecting Tomato Seedlings Resistant to Bacterial Canker. A. M. Hibberd, Queensland Department of Primary Industries, G.P.O. Box 46, Brisbane, Australia 4001. J. B. Heaton, G. P. Finlay, and S. R. Dullahide. Queensland Department of Primary Industries, G.P.O. Box 46, Brisbane, Australia 4001. Plant Dis. 76:1004-1007. Accepted for publication 22 April 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992. DOI: 10.1094/PD-76-1004.

Infiltrations of suspensions of inocula (10³–10⁸ cfu/ml) into leaflets and stems were used to evaluate resistance to Clavibacter michiganensis subsp. michiganensis in 4- to 5-wk-old tomato seedlings. Disease increased at slower rates in infiltrated tissues of Heinz 2990 than in Floradade and Morden with all concentrations except 10⁸ cfu/ml in leaflets and 10³ and 10⁴ cfu/ml in stems. Seedlings with low disease severity were selected from a segregating backcross population derived from Heinz 2990 following infiltrations of leaflets and stems with 10⁵ and 10⁸ cfu/ml, respectively. In field experiments, plants were inoculated by leaf excision with a scalpel dipped in inoculum of 10⁸ cfu/ml. Heinz 2990 developed less disease (P < 0.01) than Floradade and Morden. Less disease (P < 0.01) also developed on selfed progeny of previously selected backcross plants than on the susceptible parent Grosse Lisse, and segregation for resistance occurred among nonselected backcross plants. Disease severity levels in field-grown plants were higher (P < 0.01) in Morden than in Floradade, and fruiting was earlier and more concentrated in time in Morden. The test of seedlings in the greenhouse has potential for rapid screening of lines for partial resistance and in tomato breeding programs.