Twenty-eight official tobacco (Nicotiana tabacum L.) cultivars, 35 candidate cultivars and one breeding line were evaluated for resistance to Phytophthora parasitica var. nicotianae (Breda de Haan) Tucker at field locations in Georgia, South Carolina, and North Carolina and, in greenhouse tests in North Carolina and Virginia. Cultivars which were considered resistant when they were released ranged from 49 to 100% killed in field locations and 59-100% killed in a greenhouse test. New candidate cultivars ranged from 100% killed to almost completely resistant to black shank. Correlation coefficients of % disease for field data vs. greenhouse data on candidate cultivars ranged from 0.57 to 0.76 (P =0.0001). Data for % disease between field locations had correlation coefficients from 0.81 to 0.86 (P = 0.0001). The Scott-Knot procedure of cluster analysis was used to separate means into distinct groups without overlapping. This method of statistical analysis facilitates researchers and extension specialists to give verbal ratings for cultivars according to their resistance to black shank.

(Full article published with kind permission from "Tobacco International")