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Techniques

Use of Detached Leaves to Evaluate Tobacco Haploids and Doubled Haploids for Resistance to Tobacco Mosaic Virus, Meloidogyne incognita, and Pseudomonas syringae pv. tabaci. Rebeca C. Rufty, Assistant professor, Department of Crop Science, North Carolina State University, Raleigh 27695; E. A. Wernsman(2), and G. V. Gooding, Jr.(3). (2)Professor, Department of Crop Science, North Carolina State University, Raleigh 27695; (3)Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695. Phytopathology 77:60-62. Accepted for publication 16 May 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-60.

Development of disease-resistant cultivars in self-pollinated crops like tobacco (Nicotiana tabacum) can be greatly accelerated by evaluating populations of haploid plants derived from F₁ hybrids resistant to various diseases. A limitation of haploid breeding is the need to assess reactions to multiple pathogens on single plants. To avoid confounding systemic or lethal effects from inoculations with multiple pathogens, detached leaves were inoculated separately with tobacco mosaic virus and Pseudomonas syringae pv. tabaci. Resistance to Meloidogyne incognita was identified by the associated reactions of detached leaves to the M^SN^R strain of potato virus Y. Detached leaves were maintained by immersing their petioles in water until symptoms appeared. Symptoms in detached leaves were similar to those in intact plants, and disease reactions corresponded with whole-plant determinations. The technique can also be used with doubled haploid or diploid populations segregating for disease resistance. The original intact plants with identified resistance may be evaluated for other traits, and susceptible genotypes may be discarded. Field evaluations for agronomic characteristics can then be performed on a population fixed for disease resistance genes.