VIEW ARTICLE

Resistance

Nontransmissibility to Regenerants from Protected Tobacco Explants of Induced Resistance to Peronospora hyoscyami. J. A. Lucas, Department of Plant Pathology, University of California, Riverside 92521, Current address of senior author: Department of Botany, University of Nottingham, NG7 2RD, UK; T. E. Dolan(2), and M. D. Coffey(3). (2)(3)Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 75:1222-1225. Accepted for publication 21 May 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-1222.

Tobacco plants, Nicotiana tabacum, were protected against blue mold, caused by Peronospora hyoscyami f. sp. tabacina, by injection of the lowest stem internode with a sporangial suspension of the pathogen. Shoot-tip and leaf explants from protected tobacco were taken for rapid propagation through tissue culture, or used to establish callus lines. Regenerants obtained from protected tissues by rapid propagation were as susceptible to foliar challenge with sporangial inoculum of the fungus as similar regenerants derived from unprotected control explants. Regenerants produced by organogenesis from callus lines were also highly susceptible, although spore production per square centimeter of leaf area was significantly less in the case of protected regenerants. These results suggest that the expression of systemic induced resistance to blue mold depends mainly upon an active lesion being present in protected plants rather than an irreversible change in the inherent resistance expression of tobacco tissues.