VIEW ARTICLE

Resistance

Rating General Resistance on a Single-Plant Basis. W. Q. Loegering, Pathologist, Departments of Plant Pathology and Agronomy, University of Missouri, Columbia 65201; D. A. Sleper(2), James M. Johnson(3), and K. H. Asay(4). (2)(3)(4)Agronomist, Research Technician, and former Agronomist, respectively, Departments of Plant Pathology and Agronomy, University of Missouri, Columbia 65201, (4)Present address: U.S. Department of Agriculture, Agricultural Research Service, Logan, UT 84322. Phytopathology 66:1445-1448. Accepted for publication 7 June 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1445.

A method of rating single plants for general resistance was devised which directly compares, over time, the relative amount of disease on a single plant with all other plants in the test. The method is simple and rapid and has been found to be reproducible between 2 years and among seven judges. It involves taking notes many times (7-14) throughout the disease cycle on the basis of S = standard for the most disease as observed from a standing position on each day notes are taken, and L = less than standard. The number of times during the season that a plant is rated S is the disease index. If the ratings obtained with the method correlate with relative disease incidence in populations, it would make possible selecting for general resistance on a single-plant basis in a breeding program.