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Effect of Inoculum Concentration on Resistance of Lima Bean to Rhizoctonia solani. H. L. Warren, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Purdue University, West Lafayette, Indiana 47907; Phytopathology 65:341-345. Accepted for publication 16 October 1974. DOI: 10.1094/Phyto-65-341.

The effect of inoculum concentration of Rhizoctonia solani on resistant and susceptible lima bean cultivars was determined. A linear relationship between inoculum concentration, disease severity, and seedling infection was observed with Jackson Wonder, a resistant cultivar. The relationship between disease severity and seedling infection for Fordhook 242, a susceptible cultivar, was linear up to 30% and 50% inoculum concentration, respectively. Low concentrations of inoculum are sufficient to test selections of lima beans for resistance to Rhizoctonia. In addition, at low concentrations, seedlings intermediate in reaction can be separated.