Evaluation of Peanut Genotypes for Resistance to Southern Stem Rot Using an Agar Disk Technique1

Abstract Six tests were conducted at two locations over 3 yr using an agar disk technique. Multiple disease assessments were made with a 1 to 5 scale, allowing the use of areas under the disease progress curve for genotype comparisons. Of the 11 genotypes evaluated, four were commercial cultivars. The cultivar Florunner was highly susceptible, Southern Runner exhibited a moderate level of partial resistance, Early Bunch was slightly more resistant than Southern Runner, and Marc I was less resistant than Southern Runner. The runner line UF91108 and the virginia lines F79/4-6-2-1-1-Z1, F79/4-6-2-1-1-Z16, and F84/49-2-2 all appear to have similar levels of resistance to stem rot. The runner breeding lines UF85112 and UF86107 had less disease over the six tests than any other genotypes. The agar disk technique worked well in the field, allowing selection of breeding lines with resistance to stem rot. Lines that exhibited good resistance in the six tests will be useful germplasm resources for a cultivar improvement program.