Components of Resistance in Peanut to Cercospora arachidicola. M. D. Ricker, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. M. K. Beute, and C. L. Campbell, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 69:1059-1064. Accepted for publication 1 July 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1059.

Twenty genotypes of peanut (Arachis hypogaea) were tested in the greenhouse and ranked in increasing order of resistance to early leaf spot (Cercospora arachidicola) for each of the following components of rate-reducing resistance: number of lesions per leaf, lesion diameter, latent period, time until leaflet defoliation, and sporulation. With the exception of lesion diameter, differences among genotypes were found for all components. Number of lesions was influenced greatly by environment and therefore was an unreliable means to evaluate these genotypes in the greenhouse. Ranking of genotypes for latent period was consistent with two methods of measuring latent period: time until at least two lesions sporulated and time until 50% of the lesions sporulated. Genotypes with longer latent periods and fewer sporulating lesions generally had a longer period until leaflet defoliation. Genotype NC 3033 showed the greatest overall resistance to early leaf spot.