Accuracy, Precision, and Correlation to Yield Loss of Disease Severity Scales for Corky Root of Lettuce

A method for comparing disease severity scales using accuracy, precision, and correlation to yield loss was tested using disease assessment scales developed for corky root of lettuce. Two qualitative interval scales, a seven-level scale developed for assessing corky root severity of mature lettuce plants and a ten-level scale developed for screening seedlings for resistance 1 mo after inoculation, were compared with a 12-level Horsfall-Barratt (H-B) scale based on the percentage of the taproot area with corky root symptoms (...)