Use of Detached Leaves to Evaluate Tobacco Haploids and Doubled Haploids for Resistance to Tobacco Mosaic Virus,Meloidogyne incognita,andPseudomonas syringaepv.tabaci
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 MSNR 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.