VIEW ARTICLE

Techniques

Resistance to Black Shank in the Field Predicted by a Test of Tobacco Seedlings. G. S. Taylor, Assistant to the director, Connecticut Agricultural Experiment Station, New Haven 06504; P. E. Waggoner, director, Connecticut Agricultural Experiment Station, New Haven 06504. Phytopathology 69:1132-1134. Accepted for publication 14 May 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1132.

Roots of 10 seedlings of 17 lines of tobacco in petri dishes were inoculated with 1,000–5,000 zoospores of Phytophthora parasitica var. nicotianae. Although the relation between the number of seedlings killed and the number of plants of the same lines that became diseased in the field was strongly nonlinear, the relation between the calculated numbers of infections of seedlings and infections of plants in the field was more nearly linear (r = 0.86). If lines estimated by the multiple infections correction to have more than 20 infections per 10 seedlings had been discarded, all resistant lines—and only resistant lines—would have been kept.